KR20030024685A - Coating system for high temperature stainless steel - Google Patents

Abstract

MCrAlX or MCrAlXT, wherein M is nickel, cobalt, iron or mixtures thereof, X is yttrium, hafnium, zircon, lanthanum, scandium or combinations thereof, T is silicon, tantalum, titanium, platinum, palladium, rhenium, By coating the steel with a coating of molybdenum, tungsten, niobium or a combination thereof, for example carbon steel and stainless steel from coking and corrosion at high temperatures under corrosive environments during ethylene production by pyrolysis of hydrocarbons or reduction of oxide ores, In particular, a method for protecting high temperature stainless steel is provided. The coating and substrate are heat treated at about 1000 to 1200 ° C. for at least about 10 minutes, preferably about 20 minutes to 24 hours, effective to metalbond the overlay coating to the substrate and form the microstructure of the multiphase. The coating is preferably aluminum plated by depositing an aluminum layer thereon and subjecting the resulting coating to an oxidation treatment for an effective time to form an alumina surface layer at a temperature of about 1000 ° C. or higher. Interlayers containing aluminum in the middle can be deposited directly onto the substrate prior to deposition of the overlay coating, and heat treated with the coating to form a protective interlayer between the stainless steel substrate and the coating and to disperse nitride formation at the substrate / coating interface. do. In addition, the coating may be deposited on the substrate, the micronized powder of MCrAlXT may be metal bonded to the substrate by plasma grown arc deposition can omit the need for a separate heat treatment. In addition, a powder composition blended to produce the desired MCrAlXT alloy can be applied to the substrate.

Description

Coating System for High Temperature Stainless Steels {COATING SYSTEM FOR HIGH TEMPERATURE STAINLESS STEEL}

Stainless steel is an alloy group based on iron, nickel and chromium as main components and may include carbon, tungsten, niobium, titanium, molybdenum, manganese and silicon as additives to obtain specific structures and properties. Its main types are named as martensitic, ferritic, duplex and austenitic steels. Austenitic stainless steels are generally used where high strength and corrosion resistance are required. One group of these steels is collectively known as a high temperature alloy (HTA) and is generally used in industrial processes operating at temperatures above 650 ° C. extending to a temperature limit of ferrous metallurgy of about 1150 ° C. Used. The main austenite alloys used have a composition of 18 to 42% by weight of chromium, 18 to 48% by weight of nickel, the balance of iron and other alloying additives iron, nickel or chromium. Typically, high chromium stainless steel has about 31 to 38 weight percent chromium and low chromium stainless steel has about 20 to 25 weight percent chromium.

The bulk composition of the HTA is intended towards physical properties such as creep resistance and strength, and chemical properties of the surface such as corrosion resistance. Corrosiveness takes many forms, depending on the operating environment and includes carburization, oxidation and sulfidation. The bulk alloy is protected by a surface rich in chromium oxide (chromia). The specific composition of the alloy used means optimized physical properties (bulk) and chemical properties (surface). The ability to deal with the chemical properties of surfaces through surface alloys and physical properties through bulk compositions will provide many opportunities for improving material performance in many harsh service industrial environments.

Surface alloying can be performed by using a variety of coating processes to deliver the correct combination of materials to the component surface in an appropriate proportion. These materials need to be pre-engineered or alloyed with the bulk matrix in a controlled manner to obtain a microstructure that can provide the desired benefits. Such control requires control of relative phase diffusion and overall phaseevolution between all components. Once formed, the surface alloy can be activated and reactivated as needed by reactive gas heat treatment. Since both surface alloying and surface activation require significant movement of atomic components at temperatures in excess of 700 ° C., HTA products can be most beneficial from the process by their intended high temperature operating capabilities. This process can also be used for products intended for colder operating temperatures, but may require post heat treatment after surface alloy treatment and activation to reestablish physical properties. .

Surface alloys or coating systems may be intended to provide a wide range of benefits to end users, starting with commercial base alloy chemistry and ranging from properly designing the coating system to meet specific performance requirements. Characteristics that can be intended for such systems include: good high temperature gas corrosion resistance (carbonization, oxidation, sulfidation), controlled catalytic activity; And high temperature erosion resistance.

There are two metal oxides mainly used for protecting the alloy at high temperatures, ie chromia and alumina, or mixtures thereof. The composition of stainless steel for high temperature use is tailored to provide a balance between good mechanical properties and good oxidation and corrosion resistance. Alloy compositions capable of providing an alumina scale are preferred when good oxidation resistance is required, while compositions capable of forming chromia scales are selected for resistance to high temperature corrosion conditions. Unfortunately, the addition of high amounts of aluminum and chromium to the bulk alloy cannot maintain good mechanical properties, and coatings containing normally aluminum and / or chromium are applied to the bulk alloy to provide the desired surface oxides.

From a material point of view, one of the most precise industrial processes is the production of olefins such as ethylene by hydrocarbon steam pyrolysis (cracking). Hydrocarbon feedstocks such as ethane, propane, butane or naphtha pass through a furnace coil made of welded tubes and release tubes mixed with steam. These coils are heated on the outer wall and the heat is conducted to the inner wall surface leading to the pyrolysis of the hydrocarbon raw material to produce the desired product mixture in the temperature range of 850 to 1150 ° C. An undesirable side effect of this process is the production of coke (carbon) on the coil inner wall surface. There are two main types of coke: Catalytic coke (or filamentous coke), which grows in long thread form when promoted by a catalyst such as nickel or iron, and forms gas in gas Amorphous coke plated from the flow. Upon pyrolysis of a small amount of feedstock, the catalytic coke may account for 80-90% of the deposit, providing a large surface area for amorphous coke recovery.

Coke acts as a thermal insulator that needs to continuously increase the tube outer wall temperature to maintain throughput. Coke is produced in excess so that the tube surface temperature can no longer be increased, and problems arise when the furnace coil goes offline to remove coke (decoking) by combustion. The decoking process typically lasts for 24 to 96 hours, is required once every 10 to 90 for small feedstocks, and considerably longer for large feedstocks.

During the decoking period, there is no production of salable products and this represents a major economic loss. In addition, the decoking process accelerates the decomposition of the tube, which shortens the life. In addition to the inefficiencies introduced in the process, coke formation also results in accelerated carbonization of the tube inner wall, other types of corrosion and erosion. This carbonization is due to the diffusion of carbon into the steel to form a brittle carbide phase. This process leads to volume expansion, and embrittlement causes loss of strength and the possibility of crack initiation. As carbonization increases, the alloy's ability to provide some coking resistance through the formation of a chromium based scale degrades. At normal operating temperatures, half of the wall thickness of some steel pipe alloys can be carbonized in about two years of installation. Typical tube life is on the order of three to six years.

Surfaces of aluminum plated, silica coated steel, and steel rich in manganese oxide or chromium oxide have proven to be advantageous in reducing catalytic coke formation. Alonizing ^™ , or aluminum plating, involves the diffusion of aluminum into the alloy surface by pack cementation, a chemical vapor deposition technique. The coating provides an alumina scale that is effective in reducing catalytic coke formation and protecting it from oxidation and other forms of corrosion. The coating is not stable at temperatures such as those used in ethylene furnaces, and is also brittle and tends to spread or diffuse into base alloy matrices. In general, compression carburizing is limited to the deposition of one or two elements, and co-deposition of many elements is very difficult. Commercially, it is limited to the deposition of a few elements, mainly aluminum. Several studies have been carried out on the co-deposition of two elements, for example chromium and silicon. Another approach for applying aluminum diffusion coatings to alloy substrates is described in US Pat. No. 5,403,629 (P. Adam et al.). According to this patent, a method for depositing metallic interlayers, for example by sputtering, on the surface of a metal component is described in detail. Subsequently, an aluminum diffusion coating is deposited on the interlayer.

Another diffusion coating has been studied. In a paper by MC Meelu and MH Lorretto entitled "The Effect of Time at Temperature on Silicon Titanium Diffusion Coating on IN738 Base Alloy" in "Processing and Properties," Si-Ti coating applied by compression carburizing at high temperature over an extended period of time. The evaluation of is described.

Prior to that, the benefits of aluminum plating MCrAlX coatings on superalloys have been documented in detail for improved oxidation and corrosion resistance. For example, EP 897996 describes improving the high temperature oxidation resistance of MCrAlY on superalloys by applying an aluminide top coat using chemical vapor deposition techniques. Similarly, U.S. Patent No. 3,874,901 discloses an aluminum overlay on MCrAlY using electron beam-physical vapor deposition to enrich aluminum on the near surface of MCrAlY and seal the structural defects of the overlay to seal the high temperature corrosion resistance of the coating. And coating systems of superalloys that improve oxidation resistance. These systems all relate to improving the oxidation and / or high temperature corrosion resistance imparted to superalloys by depositing MCrAlY thereon. These references are not related to the improvement of the coking or corrosion resistance of high temperature stainless steel alloys used in the petrochemical industry.

The main difficulty in finding an effective coating is that many of the applied coatings do not tend to adhere to the tube alloy substrate under certain high temperature operating temperatures to hydrocarbon pyrolysis. In addition, the coating lacks the necessary resistance to some or all of thermal stability, thermal shock, high temperature erosion, carbonization, oxidation and sulfidation. Commercially available products for the production of olefins by hydrocarbon steam pyrolysis and for the direct reduction of iron ore should be able to provide the necessary coking and carbonization resistance over an extended operating life while exhibiting thermal stability, high temperature erosion resistance and thermal shock resistance.

Underground oil and gas drilling, production and casing tube strings and extensions are made of carbon steel that is susceptible to corrosion and erosion under a hostile subterranean environment. Therefore, there is a need to coat a protective surface on this carbon steel component.

Plasma transferred arc surfacing (PTAS), for example as described in US Pat. Nos. 4,878,953 and 5,624,717, is a technique used to apply coatings of different compositions and thicknesses onto conductive substrates. The material is supplied in the form of powder or wire to a torch that generates an arc between the anode and the workpiece. The arc generates a plasma that heats the surface of the powder or wire and the substrate to melt them and form a liquid puddle that forms a welded coating upon solidification. By varying the feed rate of the material, the speed of the torch, the distance to the substrate, and the current flowing through the arc, thickness, microstructure, density, and other coating properties can be controlled (P. Harris and BL Smith, Metal Construction 15 ( 1983) 661-666). This technique not only surface-treats MCrAlY on top of nickel-based superalloys (GA Saltzman, P. Sahoo, Proc. IV National Thermal Spray Conference, 1991, pp 541-548), but also exhaust valves and other internal combustion engine cylinders. It has been used in some applications to prevent high temperature corrosion, including surface treatment of high chromium nickel based coatings on parts (Danish Patent 165,125, US Pat. No. 5,958,332).

Air Force Materials Laboratory performed by Air Force Materials in the "Controlled Composition Reaction sintering Process for Production of MCrAlY coatings" described in Technical Report AFML-TR-76-91 and Solar Division of International Harvester Company Research Laboratory in San Diego, California The process evaluated by the Materials Laboratory in a report entitled "Development and Evaluation of Process for Deposition of Ni / Co-Cr-AlY (McrAlY) Coatings for Gas Turbine Components" in Technical Report AFML-TR-79-4097 Has been used to make coatings of the type MCrAlY. The gas turbine blades were coated with an atomized MCrY-alloy using a slurry containing an organic binder. The coated turbine blade was then embedded in a pack consisting of aluminum oxide (Al ₂ O ₃ ), aluminum powder (Al), and ammonium chloride (NH ₄ Cl). The pack was heated in a controlled atmosphere under controlled time and temperature conditions to produce an MCrAlY-coating similar to a coating deposited by standard PVD processes. The main problem that arises when this process is used in gas turbines is that the thickness of the coating varies and is difficult to control. Al is also added to the coating via a pack aluminizing plating CVD process, which is environmentally unfriendly.

FIELD OF THE INVENTION The present invention relates to coating systems for forming protective surfaces for carbon steel and stainless steel, more specifically providing corrosion resistance and erosion resistance, and providing olefin production and direct ore It is directed to providing a metal alloy coating on the inner wall surfaces of hot stainless steel pipes and fittings to form surfaces that reduce the formation of catalytic coking in hydrocarbon treatments such as reduction. This protection system also has applications for carbon steel. For example, in underground oil and gas applications, the protection system improves the erosion and corrosion properties compared to commonly used carbon steels.

The process of the invention and the product produced thereby are described with reference to the accompanying drawings:

1 is a micrograph of a NiCrAlY coated cross section deposited on a stainless steel substrate;

FIG. 2 is a micrograph after heat treatment of the NiCrAlY coating shown in FIG. 1; FIG.

3 is a micrograph of a NiCrAlY coating cross section with an aluminum layer deposited over the NiCrAlY coating;

4 is a micrograph after heat treatment of a NiCrAlY coating with an aluminum layer;

5 is a micrograph of a diffusion coating deposited on a stainless steel substrate having a NiCrAlY coating deposited on the diffusion coating and an aluminum layer deposited on the overlay coating;

6 is a micrograph after heat treatment of the composite coating shown in FIG. 5;

7 is a micrograph of the interface between NiCrAlY deposited by plasma grown arc on HTA alloy 900B;

8 is a micrograph of the NiCrAlY top surface after aging for 500 hours in air at 1150 ° C .;

9 is a micrograph of a bulk microstructure after 500 hours of aging in air at 1150 ° C .;

10 is a micrograph of the interface between NiCrAlY coating and low chromium stainless steel after aging for 500 hours in air at 1150 ° C .;

11 is a micrograph of the interface between a NiCrAlY coating and high chromium stainless steel after aging for 500 hours in air at 1150 ° C .;

12 is a micrograph after heat treatment of the interface between diffusion coatings on a stainless steel substrate with a NiCrAlY coating on the stainless steel substrate.

Accordingly, it is an object of the present invention to provide beneficial properties to carbon steels and stainless steels through surface alloying to remove or reduce the catalytic formation of coke on the inner surfaces of tubes, pipes, release tubes and other accessory furnace materials, and catalytic coke Minimizing the number of formation sites and substantially improving the surface properties by improving the quality of the alumina scale on the surface alloy coating deposited on the steels. The alloy coating according to the invention is represented in the petrochemical industry by ethylene production, the production of other hydrocarbon-based products, for example olefins by hydrocarbon steam pyrolysis, which is represented by the direct reduction of iron oxide ore into metal iron in a carbon-containing atmosphere. Particularly suitable for high temperature stainless steel applications for production.

When the high temperature stainless steel pipes used in the ethylene furnace were coated with these materials, improvements in the coking, carbonization and high temperature erosion resistance of the tubes were observed.

Another object of the present invention is to increase the carbonization resistance of HTA used in tubes, pipes, release tubes and other accessory furnace materials during use.

It is another object of the present invention to provide improved thermal stability, erosion resistance and thermal shock resistance to increase the lifetime of improved performance derived from surface alloy treatment under commercial conditions.

According to the present invention, an MCrAlX alloy coating is formed directly on a high temperature stainless steel alloy substrate or an intermediate interlayer, and then subjected to heat treatment to form a coating microstructure, and to a surface alloy structure that can be formed by metal bonding the coating onto the substrate. Four embodiments are provided. When the tubes used in the ethylene furnace were treated by the above method, improvement in the coking resistance, carbonization resistance, and high temperature corrosion resistance of the tubes was observed.

A first embodiment of the surface alloy structure according to the invention is MCrAlX, wherein M is nickel, cobalt, iron or mixtures thereof, X is yttrium, hafnium, zirconium, lanthanum, scandium or their A coating material is applied to a high temperature stainless steel alloy substrate, and the MCrAlX coating and the substrate are appropriately heat treated.

A second embodiment of the surface alloy structure according to the present invention deposits a layer of aluminum or aluminum alloyed with silicon, or aluminum alloyed with at least one of silicon and chromium and titanium, onto the MCrAlX coating and Heat treating the alloy, MCrAlX coating, and the composition of the substrate to form a coated microstructure.

A third embodiment of the surface alloy structure according to the present invention includes depositing an interlayer on a high temperature stainless steel alloy substrate under an MCrAlX coating. The nitrogen and carbon content of standard high temperature stainless steel alloys can lead to the formation of unwanted brittle nitride and carbide layers at the coating / substrate interface. The deposition of interlayers containing stable nitride formers under the MCrAlX coating will act to disperse the nitride precipitates. This is more preferred compared to continuous nitride layers. The interlayer will also act to disperse carbide precipitates. This is more preferred compared to the continuous carbide layer at the coating / substrate interface. The interlayer will also increase the adhesion of the MCrAlX coating to the substrate and reduce the surface preparation content required for coating deposition. An MCrAlX alloy is deposited on the interlayer, an aluminum layer is deposited on the MCrAlX coating, the coating system is heat treated to diffuse aluminum into the MCrAlX coating and the layers and the substrate are metal bonded to each other to obtain the desired microstructure.

A fourth embodiment of the surface alloy structure according to the present invention comprises depositing a blended powder composition to produce an MCrAlXT-alloy through a reactive sintering process directly on the substrate surface.

Each of the above embodiments is pre-oxidized to form a protective outer layer of predominantly X-alumina. The X-alumina layer is very effective in reducing or eliminating the formation of catalytic coke. These surface alloys are compatible with high temperature commercial processes at temperatures up to 1150 ° C. which are applied in the production of olefins, for example by hydrocarbon steam pyrolysis represented by ethylene production.

In a broad aspect, the process according to the invention for providing protective and inert coatings on carbon steel and high temperature stainless steel substrates at temperatures of up to 1150 ° C. comprises 0-40% by weight of chromium, about 3-30% by weight. Aluminum and at most about 5.0% by weight, preferably at most about 3% by weight, more preferably at about 0.25-1.5% by weight of yttrium, hafnium, zirconium, lanthanum, scandium, or a combination thereof, MCrAlX alloy having a balance M Wherein M is nickel, cobalt or iron or mixtures thereof, and X is a continuous coating of yttrium, hafnium, zirconium, lanthanum, scandium or combinations thereof. The MCrAlX alloy is not particularly limited but may be deposited by various methods including thermal spray, plasma raised arc, physical vapor deposition, and slurry coating techniques. Preferably, the overlay and substrate are heat treated at a soak temperature in the range of about 1000 to 1200 ° C. for at least 10 minutes, more preferably about 20 minutes to 24 hours.

The coating is about 50 to 500 μm, preferably about 120 to 250, for example by magnetron sputtering physical vapor deposition on the substrate in the temperature range of about 200 to 1000 ° C., preferably about 450 ° C. Is deposited to a thickness of about 150 μm, most preferably about 150 μm, and the coating and substrate are heated to the desired aging temperature. Preferably, MCrAlX is NiCrAlX and has about 12-22 weight percent chromium, about 8-15 weight percent aluminum and about 0.8-1 weight percent yttrium, balance nickel.

The high temperature stainless steel substrate comprises about 18 to 38 weight percent chromium, 18 to 48 weight percent nickel, balance iron and alloying additives, preferably high chromium stainless steel having 31 to 38 weight percent chromium or Low chromium steel with 20 to 25 weight percent chromium.

According to another embodiment of the present invention, a high temperature stainless steel substrate having a continuous coating of the MCrAlX alloy having a thickness of about 120 to 250 μm is aluminum plated by depositing an aluminum layer thereon, and a coating having aluminum thereon; The substrate is heat treated for about 20 minutes to 24 hours in a aging temperature range of about 1000 to 1200 ° C. in an oxygen free atmosphere to metal bond the coating to the substrate and form a multiphased microstructure. The aluminum layer is deposited on the coating by a magnetron sputtering physical vapor deposition at a temperature of about 200 to 500 ° C., preferably about 300, preferably up to about 50% of the coating thickness, preferably about 20% of the coating thickness. The coating and substrate together with the aluminum layer are then heated to aging temperature.

According to another embodiment according to the method of the invention, a continuous interlayer is first deposited on the substrate prior to coating, dispersing the formation of the nitride or carbide layer at the coating / substrate interface. An effective interlayer is about 35 to 45 weight percent aluminum, at least one of 5 to 20 weight percent titanium or chromium, 40 to 55 weight percent silicon, preferably about 35 to 40 weight percent aluminum, about 5 to Consisting of 15 weight percent titanium and about 50-55 weight percent silicon, deposited on a high temperature stainless steel substrate, as described in co-pending US application Ser. No. 08 / 839,831, incorporated herein by reference, A continuous MCrAlX alloy coating is deposited on the diffusion coating and an aluminum layer is deposited on the MCrAlX alloy coating.

The interlayer is preferably deposited by physical vapor deposition in the temperature range of 400 to 600 ° C or 800 to 900 ° C, preferably 450 or 850 ° C. Thermal spray deposition techniques may also be used. The interlayer is then heated to the aging temperature at a rate of temperature rise of at least 5 ° C./min, preferably at a rate of 10 to 20 ° C./min to form a coated microstructure. The MCrAlX coating, preferably the aluminum layer, is deposited on the interlayer by physical vapor deposition and then heat treated to form a multiphase microstructure and metal bonded to the coating system.

The system can then be heated for an effective time to form a surface layer of VII-alumina thereon in a continuous or separate step at a temperature range of at least about 1000 ° C., preferably 1000 to 1160 ° C., in an oxygen-containing atmosphere. have.

The interlayer is deposited to a thickness of about 20 to 100 μm, preferably about 20 to 60 μm. The interlayer forms a diffusion barrier between an enrichment pool containing an intermetallic of base alloy and silicon and one or more titanium or aluminum and base alloy elements at aging temperatures ranging from about 1030 to 1150 ° C. In order to be heated for a valid time. Preferably, the interlayer comprises about 6 to 10 weight percent silicon, 0 to 5 weight percent aluminum, 0 to 4 weight percent titanium and about 25 to 50 weight percent chromium, balance iron and nickel and other bases. It contains an alloying element.

Another process for producing a similar coating system is an inert atmosphere, a aging temperature of about 1030-1160 ° C., to sequentially deposit the interlayer, MCrAlX alloy coating, and suitably aluminum, to form microstructures and bond the coatings. Heat treatment in the range.

It is therefore a further object of the present invention to properly provide a surface alloy MCrAlX coating on HTA in a single process step without separate heat treatment.

In a broad aspect, this embodiment according to the method of the present invention for providing a protective and inert coating to high temperature stainless steel comprises about 0 to 40% by weight of chromium, by plasma grown arc deposition of the coating on a high temperature stainless steel substrate. Preferably from about 10 to 25 weight percent chromium, from about 3 to 30 weight percent aluminum, preferably from about 4 to 20 weight percent aluminum, up to about 5 weight percent X, preferably up to about 3 weight percent CrAlX alloy having X, more preferably 0.25 to 1.5% by weight of X, the balance M, wherein M is nickel, cobalt or iron or mixtures thereof, X is yttrium, hafnium, zirconium, lanthanum, scandium or these Providing a protective and inert coating over the high temperature stainless steel comprising metal bonding the continuous coating.

The MCrAlX may be 0-25 wt% chromium, about 3-40 wt% aluminum, about 3 wt% or less yttrium, and FeCrAlY having a balance substantially iron.

The MCrAlX is preferably NiCrAlY and has about 12 to 25 weight percent chromium, about 4 to 15 weight percent aluminum and about 0.5 to 1.5 weight percent yttrium and the balance nickel.

According to one preferred embodiment of the present invention, a dense coking resistant NiCrAlY alloy coating is deposited on the HTA tube in a single step by plasma grown arc deposition, resulting in a progressive metal bond between the alloy coating and the substrate. The preferred final thickness of the coating is about 0.02 to 6 mm thick. Preferred thicknesses to maintain the powder cost reasonably and not to significantly reduce the inner diameter of the tube range from 80 to 500 μm.

By introducing an oxygen-containing gas such as air at a temperature of about 1000 ° C. or higher upon heating the substrate and coating in a separate step at a temperature of about 1000 ° C. or higher in an oxidizing gas atmosphere such as air, or at an operating temperature of about 1000 ° C. or higher during commercial use The introduction or presence of an oxygen-containing gas provides a NiCrAlY alloy coating to provide an aluminum source for providing a X-alumina based layer on its surface. The more complete the aluminum scale, the better the caulking and corrosion resistance. Therefore, the properties can sometimes be improved by another aluminum plating step.

However, according to another embodiment of the present invention, a high temperature stainless steel substrate having a continuous coating of the MCrAlX alloy having a thickness of about 50 to 2000 μm, preferably about 80 to 500 μm is made of aluminum, or about 60% by weight. Up to about 15% by weight of silicon, or preferably an aluminum layer alloyed with at least about 60% by weight of silicon and one or more of about 30% by weight of chromium and titanium Aluminum plating may be performed by depositing on a plasma grown arc coating, such as by thermal spraying or magnetron sputtering physical vapor deposition, to a thickness of 50% or less, preferably about 20% or less of the coating thickness. The system can be heated in an oxygen-containing atmosphere for a time sufficient to form a surface layer of X-alumina thereon in a continuous or separate post step.

Another object of the present invention is MCrAlX further having a T element selected from the group consisting of silicon and / or tantalum, titanium, platinum, palladium, rhenium, molybdenum, tungsten, niobium or combinations thereof to enhance the coating properties. To provide an alloy.

According to this aspect of the invention, about 0-40% by weight of chromium, about 3-30% by weight of aluminum, about 5% by weight or less of X, 0-40% by weight of silicone, and about 10% by weight or less of T , MCrAlXSiT alloy having a balance of M, where M is nickel, cobalt, iron or mixtures thereof, X is yttrium, hafnium, zirconium, lanthanum, scandium or combinations thereof, and T is tantalum, titanium, platinum, palladium, Rhenium, molybdenum, tungsten, niobium, or a combination thereof). Preferably, the MCrAlXSiT alloy has about 10-25 wt% chromium, 4-20 wt% aluminum, 3 wt% or less X, 35 wt% or less silicon and 10 wt% or less T. More preferably, X is present in an amount of 0.25 to 1.5% by weight, silicon is present in an amount of 15% by weight or less, T is 0.5 to 8.0% by weight, most preferably 0.5 to 5.0% by weight Exists as.

In one preferred embodiment, an MCrAlXSi alloy coating comprising 22% chromium, 10% Al, 1% Y and 3% Si, and balance nickel is effective to retain aluminum within the coating. The chromium-carbide layer was promoted at the coating / substrate interface, which functions as a diffusion barrier. The presence of silicon in the MCrAlX coating also improved the chromium-based scale produced by the overlay coating.

It is another object of the present invention to apply the blended powder slurry composition to a substrate to produce the desired MCrAlX or MCrAlXSiT.

According to one preferred embodiment of the present invention according to the present invention, a mixture of two or more of the constituents of MCrAlX or MCrAlXSiT is combined with an effective amount of a binder to adhere and coat the workpiece, and the workpiece having a MCrAlX or MCrAlXSiT coating The reaction is heated to a temperature for reaction sintering of the coating and for adhesion bonding of the coating onto the workpiece.

The method of the present invention for providing protective and inert coatings on carbon and stainless steels at temperatures of up to 1150 ° C. is deposited on steel substrates, thereon about 0-25 wt% chromium, about 3-40 wt% aluminum, MCrAlXSi having about 0 to 35% by weight of silicon, and up to 5.0% by weight, preferably about 0.25 to 1.5% by weight of yttrium, hafnium, zirconium, lanthanum, scandium, or a combination thereof, at least 40% by weight of M Metal bonding a continuous overlay coating of an alloy, where M is nickel, cobalt or iron, or a mixture thereof and X is yttrium, hafnium, zirconium, lanthanum, scandium, or a combination thereof. The overlay coating is not particularly limited, but may be deposited by various methods including thermal spraying, plasma raising arc, and slurry coating techniques, where reaction sintering occurs concurrently with deposition or subsequent deposition.

If no reaction sintering occurs during deposition, the overlay coating and substrate are subsequently heat treated at a aging temperature in the range of about 500 to 1200 ° C. to initiate reaction sintering.

Inclusion of silicon in the blended powder produces low melting constituents during the reaction sintering process, causing the molten alloy to wet the surface of the substrate and form an effective diffusion bond between the coating and the substrate. It is also believed that such silicon addition prevents the formation of brittle carbides at the coating / substrate interface. At a silicon concentration of 6% by weight or more, silicon dissolves the chromium carbide formed in the substrate, and when the silicon concentration drops to 6% by weight or less, silicon randomly reprecipitates carbide by diffusion into the substrate.

It is preferred to pre-react any of the components, for example by miniaturizing chromium, aluminum and silicon, to form CrAlSi powders prior to compounding the nickel, NiCr or NiAl powders or combinations thereof. Pre-reaction of the powder slows down the exothermic reaction of the powder and reduces the amount of heat released during the reaction sintering. The coated workpiece is heated to a temperature of at least about 500 ° C. to 1100 ° C. or higher to initiate reaction sintering of the coating on the workpiece substrate, and the temperature is raised to 1200 ° C. to bond to the substrate without sharp dividing lines between the coating and the substrate. It provides a continuous impermeable coating and allows for random distribution of aluminum nitride at the coating / substrate interface.

According to another embodiment of the invention, the coating is deposited to a thickness of about 50 to 6000 μm, preferably about 120 to 500 μm, more preferably 150 to 350 μm, wherein MCrAlXSi is NiCrAlYSi blended powder, containing up to 20 wt% chromium, about 4-20 wt% aluminum, about 5-20 wt% silicon, and about 0.5-1.5 wt% yttrium, remaining at least 40 wt% nickel Have

The high temperature stainless steel comprises 18 to 38 weight percent chromium, 18 to 48 weight percent nickel, balance iron and alloying additives, preferably high chromium chrome stainless steel with 31 to 38 weight percent chromium, or 20-25% by weight of chromium low chromium steel. The workpiece substrate for use as ethylene furnace is preferably high temperature stainless steel.

According to another embodiment of the present invention, a high temperature stainless steel substrate continuously surface alloyed with MCrAlXSi alloy by reaction sintering within a thickness of about 150 to 500 µm is an aluminum surface layer, 60 wt% or less, preferably 15 wt% A surface layer of an aluminum alloy containing less than or equal to silicon, or a surface layer of an aluminum alloy containing less than or equal to 60% by weight of silicon, up to 30% by weight of chromium and titanium, and aluminum having a balance of about 20% or more by weight is deposited thereon. And, preferably, aluminum plated by heat treatment at a aging temperature in the range of about 1000 to 1160 ° C. in an oxygen free atmosphere for at least about 10 minutes. The aluminum or aluminum alloy surface layer is preferably about 50% or less, preferably about 20% or less, of MCrAlXSi thickness on the overlay at a temperature of about 200 to 500 ° C., preferably about 300 ° C., by magnetron sputtering physical vapor deposition. The substrate deposited in thickness and surface alloyed with the aluminum overlayer is heated to aging temperature.

The system is then heated for an effective period of time to form a surface layer of VII-alumina thereon continuously or in a separate post step in an oxygen-containing atmosphere, a temperature range of about 1000 ° C. or higher, preferably 1000 to 1160 ° C. Can be.

With reference to FIG. 1 and 2, 1st Embodiment of this invention is described. A continuous coating of MCrAlX deposited and metal bonded on a substrate of high temperature austenitic stainless steel is shown. MCrAlX alloy of the present invention, wherein M is a metal selected from the group consisting of iron, nickel and cobalt or mixtures thereof, X is an element selected from the group consisting of yttrium, hafnium, zirconium, lanthanum and scandium or a combination thereof ) Is about 10-25 wt% chromium, about 8-15 wt% aluminum and about 3 wt% or less, preferably about 0.25-1.5 wt% yttrium, hafnium, zirconium, lanthanum, scandium or combinations thereof, Residual amounts of iron, nickel or cobalt.

Inclusion of these elements increases the mechanical strength of the oxide scale and reduces the growth rate of the oxide while functioning as a sulfur-getter. The high temperature stainless steel substrate has a composition of iron, nickel or chromium in the composition range of 18 to 42% by weight of chromium, 18 to 48% of nickel, the balance of iron and other alloying additives, and typically about 31 to 38% by weight. High chromium stainless steel with chromium or low chromium stainless steel with about 20 to 25 weight percent chromium.

Substrates to which MCrAlX coatings are applied are, for example, high chromium and low chromium stainless steels used in ethylene furnace, which are centrifugally cast or wrought tubes or release tubes, and the coating is applied to the inner surface of such products. do. Application of the coating by magnetron sputtering physical vapor deposition has been found to enable the application of a continuous, uniform thickness and dense coating over the entire inner surface of the tube and the release tube.

The coating is deposited on the substrate as a continuous layer of substantially uniform thickness of about 50 to 350 μm, preferably about 150 μm, by magnetron sputtering in the temperature range of about 200 to 1000 ° C., preferably about 450 ° C. The coating is heated at a aging temperature in the range of about 1000 to 1200 ° C. in an oxygen free atmosphere for about 20 minutes to 24 hours to metal bond the coating to the substrate and form a multiphase microstructure.

By heating the substrate in a continuous step to introduce an oxygen-containing gas such as air at a temperature of about 1000 ° C. or more at the end of thermal aging and coating in a separate step at a temperature of about 1000 ° C. or more in an oxidizing gas atmosphere such as air, Or by the introduction or presence of an oxygen-containing gas at an operating temperature of about 1000 ° C. or higher during commercial use, the coating provides an aluminum source for providing a mu-alumina based layer at the surface thereon.

3 and 4, a second embodiment of the present invention will be described. The coating of MCrAlX is deposited on hot stainless steel as a continuous layer of substantially uniform thickness of about 50 to 350 μm, preferably about 150 μm, for example by magnetron sputtering. Aluminum, aluminum alloy containing up to about 60% by weight, preferably up to about 15% by weight of silicon, or at least 60% by weight of silicon, up to 30% by weight of chromium and titanium, the balance being about 20% by weight A uniform layer of an aluminum alloy containing at least% aluminum may be at most about 50%, preferably at least about 20%, of the coating thickness, for example by magnetron sputtering, in the temperature range of about 200 to 500 ° C, preferably about 300 ° C. It is deposited on MCrAlX in an amount of the following thickness. The substrate, coating, and aluminum layer are heated to a aging temperature in the range of about 1000 to 1200 ° C. for at least about 10 minutes, preferably about 20 minutes to 24 hours, to metal bond the coating to the substrate and form a microphase microstructure. The aluminum layer is diffused into the coating, and then sequentially heated in an oxidizing atmosphere of an oxygen-containing gas for at least 20 minutes, preferably 20 minutes to 4 hours, to oxidize the aluminum-rich layer and to a uniform thickness thereon. Forms a VII-alumina based layer to which it is attached. The oxidation of the aluminum layer is typically carried out in a separate step subsequent to the heating of the composite coating in an oxidizing atmosphere, typically at a temperature of about 1000 ° C. or more, in the range of about 1000 to 1150 ° C. for the formation of the X-alumina layer, or about 1000 Oxidation can occur during commercial operation in an oxidizing atmosphere at temperatures above < RTI ID = 0.0 >

The presence of an aluminum layer on the coating supplements the aluminum source in the MCrAlX coating to maintain a continuous, continuous alumina layer during commercial operation. The diffusion of aluminum into the coating heals the microscopic structural defects in the coating, while the abundance of aluminum in the surface of the coating proximate the surface deforms the oxide growth mechanisms, resulting in the removal of catalytic sites (such as Ni-oxide) on the protective aluminum scale. Reduce the number

5 and 6, a third embodiment of the present invention will be described. According to an embodiment according to the method of the invention, about 35 to 45% by weight of aluminum, in total about 5 to 20% by weight of one or more titanium or chromium, as described in co-pending US application Ser. No. 08 / 839,831, And continuous aluminum consisting of 40 to 55 weight percent silicon, preferably about 35 to 40 weight percent aluminum, a total of about 5 to 15 weight percent one or more titanium or chromium, and about 50 to 55 weight percent silicone. A containing interlayer is deposited on the hot stainless steel base alloy substrate, a continuous MCrAlX alloy coating is deposited on the interlayer, and an aluminum alloy comprising aluminum or nickel aluminide is deposited on the overlay alloy coating.

In this embodiment, aluminum in the interlayer can combine with nitrogen in the substrate to form a dispersion of aluminum nitride precipitates, thereby removing nitrogen released from the substrate.

The interlayer is preferably deposited by physical vapor deposition in the temperature range of 400 to 600 ° C or 800 to 900 ° C, preferably 450 or 850 ° C. The interlayer is then heated to a aging temperature at a rate of temperature rise of at least 5 ° C./min, preferably at a rate of 10 to 20 ° C./min to form a coated microstructure. The MCrAlX coating, preferably the aluminum layer, is deposited on the interlayer by physical vapor deposition and then heat treated to form a multiphase microstructure and metal bonded to the coating system.

The interlayer is deposited to a thickness of about 20 to 100 μm, preferably about 20 to 60 μm. The interlayer is effective for forming a diffusion barrier between a concentrated pool containing a base alloy and silicon and one or more intermetallic compounds of titanium or aluminum and a base alloy element at aging temperatures ranging from about 1030 to 1150 ° C. Is heated during. Preferably, the interlayer comprises about 6 to 10 weight percent silicon, 0 to 5 weight percent aluminum, 0 to 4 weight percent titanium and about 25 to 50 weight percent chromium, balance iron and nickel and other bases. It contains an alloying element.

The interlayer requires precise heat treatment to form a sufficiently layered and adherent final coating. For example, a coating comprising 10% titanium, 40% aluminum and 50% silicon by weight is deposited by using sputtering as a deposition process at a temperature of 400-500 ° C., preferably about 450 ° C. The coating can be deposited at temperatures up to 1000 ° C., but there is no reason to coat at higher temperatures unless subsequent thermal processes are performed in the same furnace. During processing, the rate of temperature rise should be in the range of at least 5 ° C per minute, typically 10-20 ° C per minute, from a maximum temperature of about 500 ° C to 5 ° C.

At temperatures between about 1130 and 1150 ° C., final layer separation of the coating occurs. The final microstructure obtained is highly dependent on temperature, but does not significantly depend on the time spent at these temperatures within a time range of about 10 minutes or more, preferably about 20 minutes to 2 hours. However, if the time at the final temperature is too short, for example less than 10 minutes, different and less desirable microstructures are obtained. At the lower limit of the temperature, 1130 ° C., void formation may occur. The optimum temperature range for the final aging temperature is 1135-1145 ° C. for at least about 20 minutes, preferably about 30 minutes to 2 hours. At higher temperatures, the diffusion barrier formed becomes unstable and at 1150 ° C. is quickly destroyed by internal diffusion of silicon. Above this temperature, aluminum diffusion may occur downward, leaving an aluminum content of 5% or less. However, below 1160 ° C., the aluminum content is still sufficient for diffusion of nitride.

If the stainless steel substrate is a annealed or cast low chromium based alloy substrate containing 20 to 25% by weight of chromium, the temperature rise rate should be the same for the high chromium based alloy substrate at about 10 to 20 ° C. per minute, but with desirable aging. The temperature is in the range of 1030 to 1160 ° C. In this embodiment, no chromium silicide-containing diffusion barrier is formed by low chromium concentration in the base alloy. Alloys having a chromium content of 20 to 25% by weight include Inco 800 ^™ series, such as 88H ^™ , 800H ^™ and 803 ^™ alloys. The minimum heating rate required does not depend on the base alloy composition.

Another embodiment of the present invention will be described with reference to FIG. 12. According to an embodiment according to the method of the present invention, an interlayer of NiCr alloy or TiAlSi alloy is deposited to a thickness of about 20 to 100 μm by magnetron sputtering on a high temperature stainless steel substrate, and the MCrAlX coating is one or two consecutive The coating is deposited on the interlayer and the resulting coated substrate is heat treated in a temperature range of 1000-1180 ° C. to bond the coating to the metal.

Embodiments according to the method of the present invention are described below with reference to the following non-limiting examples.

Tubes and coupons of 25Cr 35Ni (800H, 803, HPM, HK4M) and selected 35Cr 45Ni alloys were coated with the MCrAlX embodiments of the present invention using magnetron sputtering physical vapor deposition techniques. To improve the interfacial adhesion of the coating to the substrate by metal bonding and to form a fine-grained metal structure, the coated sample is heat-treated in hot vacuum, and then on the coating in an oxidizing atmosphere. Aluminum surfaces were deposited to form an oxide outer layer surface with caulking resistance. The upper surface layer of aluminum is deposited using the same coating technique of magnetron sputtering to improve the aluminum content of the MCrAlX coating and regenerate the protective oxide surface layer while healing a small number of structural defects in the coating to reduce the number of catalyst sites on the alumina scale. Improved the ability of the coating to make.

When coating certain centrifugally cast 25Cr-35Ni / 35Cr-45Ni alloys, an aluminum-containing diffusion coating, represented by a TiAlSi alloy, is deposited on the substrate to function as an interlayer between the substrate and the aluminum plated coating from the cast iron alloy. The coating was protected from external diffusion of released nitrogen. In addition, interlayers of NiCr alloys can be used to disperse nitride formation.

Coated and heat treated samples were characterized for uniformity, metal bonding, microstructure, thickness and composition using optical and scanning electron microscopy with energy dispersive spectroscopy by standard experimental techniques. Tests were conducted and recorded to evaluate thermal stability, oxidation resistance, carbonization resistance, thermal shock resistance, thermal fatigue resistance and creep resistance.

Small test coupons and 3-foot length tubes were tested in a simulated pyrolysis tester. A residence time of 0.4-3 seconds was used at a temperature in the range of 800-950 ° C. The run time was changed to 1-8 hours. The performance of the coated tubes and coupon samples was compared to uncoated hot alloys, ceramics and pure nickel. A 3 foot long coated tube with a 5/8 inch OD was tested in a simulated pyrolysis tester. The performance of the coated tube was compared with the uncoated hot alloy and quartz tube.

The coatings were uniformly deposited on the inner wall surface of the tube and heat treated according to the method of the invention. Coated and uncoated and release tubes in terms of metal bonding to the surfaces of commercially produced high chromium / nickel centrifugal casting tubes and annealed tubes under coking speed, carbonization, thermal shock and thermal cycling conditions and high temperature corrosion resistance. Was compared.

Example 1

1 and 2, a NiCrAlY coating 10 containing 22 wt% chromium, 10 wt% aluminum and 1 wt% yttrium, and a balance nickel, is placed on a magnetron on an Incoloy 800H ^™ stainless steel substrate 12. Deposited at 450 ° C. by sputtering to obtain an average coating thickness of 150 μm. The NiCrAlY coating and substrate were heat-treated in vacuo to 1100 ° C. at a rate of 15 ° C. per minute, and maintained at 1100 ° C. for 1 hour to prepare nickel aluminide precipitated phase 14 in the alloy matrix shown in FIG. 2.

The resulting coating was carbonized at 1080 ° C. in a CO / H ₂ atmosphere for 70 16-hour cycles. The coating showed good carbonization resistance. The coating was found to maintain thermal stability at 1150 ° C. for 1000 hours. The coating showed good mechanical properties (compared to the diffusion coating), while the stress-rupture test did not show any significant side effects on the substrate properties.

Example 2

An aluminum plated NiCrAlY coating 16 containing 22 wt% chromium, 10 wt% aluminum and 1 wt% yttrium, balance nickel was applied at 450 ° C. with magnetron sputtering on a Sandvik 800H ^™ stainless steel substrate 18. It was deposited to obtain a coating thickness of 150 to 200 mu m. An aluminum layer 22 was magnetron sputtered on the coating at 450 ° C. to obtain an average aluminum coating thickness of about 40 μm as shown in FIG. 3.

The aluminum plated NiCrAlY coating and the substrate were heat-treated in vacuo at an elevated rate of 15 ° C. per minute and held at 1100 ° C. for 1 hour to provide nickel aluminide phase 22 and alloy matrix 26 in the alloy matrix 26 adjacent to the stainless steel substrate 18. Underneath, a nickel aluminide precipitated phase was prepared. The aluminum plated coating was oxidized at about 1050 ° C. for 1 hour in air to prepare a K-alumina surface layer 28.

The coating obtained showed good carbonization resistance to withstand for 45 (+) 16-hour periods in a CO / H ₂ atmosphere. The coating was found to maintain thermal stability at 1150 ° C. for 500 hours. The coating was subjected to 1000 cycles of heat treatment at 1100 ° C. and showed good coking resistance similar to inert ceramics.

Example 3

Referring to FIG. 5, a diffusion coating 30 containing 10 wt% chromium, 40 wt% aluminum and 50 wt% silicon was placed on a Manoir XTM ^TM stainless steel substrate 32 by magnetron sputtering at 850 ° C. FIG. It deposited on and obtained the average thickness of 40 micrometers. A NiCrAlY coating 34 containing 22 wt% chromium, 10 wt% aluminum and 1 wt% yttrium, balance nickel, was deposited on the diffusion coating by magnetron sputtering at about 850 ° C. to obtain an average coating thickness of 150 μm. Got it. The aluminum layer 36 was applied to the NiCrAlY coating 34 by magnetron sputtering at 450 ° C. to obtain an average aluminum coating thickness of 20 μm.

The aluminum plated NiCrAlY coating on the diffusion coating was heat treated in a vacuum at an elevated temperature rate of 15 ° C. per minute, and maintained at 1100 ° C. for 1 hour to diffuse diffusion barrier 40 and diffusion onto substrate 32 as shown in FIG. 6. The concentrated pool 42 adjacent to the barrier 40 was obtained. Nickel aluminide phase 44 was formed by internal diffusion of the aluminum layer with the NiCrAY coating 46. At the end of the vacuum heat-treatment, air was added to form the X-alumina base layer 48 on the surface of the nickel aluminide phase 44.

The resulting coating was kept at 1150 ° C. for 500 hours to evaluate thermal stability and to test thermal shock. The coatings showed good thermal stability and good resistance to thermal shock.

Example 4

A NiCr alloy containing 50 wt% Cr and 50 wt% Ni was deposited on the Kubota KHR35CW alloy by magnetron sputtering at 450 ° C. to obtain an average thickness of 40 μm. NiCrAlY coating containing 22 wt% Cr, 10 wt% Al, 1 wt% Y, and the balance Ni was deposited at 450 ° C. by magnetron sputtering to obtain an average thickness of 60 μm, followed by 18 wt% Cr, A second NiCrAlY coating containing 15 wt% Al, 1 wt% Y and the balance Ni was deposited at 450 ° C. by magnetron sputtering to obtain an average thickness of 80 μm. The resulting coatings and substrates were heat treated at 1150 ° C. for 1 hour in vacuum.

The heat treated coating was isothermally oxidized in laboratory air for 192 hours and the coating was still in relatively good condition. The coating also showed good mechanical properties when compared to NiCrAlY without a NiCr layer.

Example 5

A TiAlSi alloy containing 20 wt% Ti, 20 wt% Al and the balance of Si was deposited on the Manior XM alloy at 850 ° C. by magnetron sputtering to obtain an average thickness of 40 μm. Thereafter, a NiCrAlY alloy containing 22 wt% Cr, 10 wt% Al, 1 wt% Y, and the balance Ni was deposited at 850 ° C. by magnetron sputtering to obtain an average thickness of 160 μm. Subsequently, the coating was heat treated at 1150 ° C. under vacuum for 1 hour to prepare the interlayer shown in FIG. 12.

The resulting coatings were isothermally oxidized in laboratory air, showing a protective effect for up to 480 hours and successfully dispersing damaging nitride phases.

Example 6

Referring to Figures 7 to 11, a continuous coating of MCrAlX was deposited on a substrate of high temperature austenitic stainless steel and metal bonded by a plasma grown arc process. The MCrAlX alloy of the present invention wherein M is a metal selected from the group consisting of iron, nickel and cobalt or mixtures thereof, X is an element selected from the group consisting of yttrium, hafnium, zirconium, lanthanum, scandium and combinations thereof 40 wt%, preferably about 10-25 wt% chromium, about 3-30 wt%, preferably about 4-20 wt% aluminum, and about 5 wt% or less, preferably about 3 wt% or less And, more preferably, about 0.5 to 1.5% by weight of yttrium, hafnium, zirconium, lanthanum, and / or scandium, the balance of iron, nickel or cobalt or combinations thereof.

Substrates to which the MCrAlX overlay coating has been applied are typically high or low chromium stainless steel centrifugal cast iron or soft iron tubes or release tubes, and the application of the coating by plasma grown arc process deposition is continuous over the entire length of the inner surface of the tubes and release tubes. It allows for uniform thickness and dense coating.

Preferred MCrAlX is NiCrAlY comprising about 12-25 weight percent chromium, about 4-15 weight percent aluminum, about 0.5-1.5 weight percent yttrium, and the balance nickel.

The deposition process for the NiCrAlY coating involves applying a powder raw material of MCrAlX composition to a base alloy substrate that forms part of the electrical circuit by a plasma growing arc process. In this process, the plasma arc melts the powder and base alloy, and argon is used as a carrier gas and a shrouding gas to prevent oxidation. The process parameters are controlled during deposition to form a melt puddle that will form a coating to the desired thickness. By the molten portion of the substrate alloy some dilution occurs which affects the final composition of the coating. In addition, it forms the desired transition zone between the base alloy and the coating which, in a scattered fashion, contains carbides and nitrides formed by diffusion of carbon and nitrogen at high temperatures operating in an ethylene furnace. This significantly reduces the risk of spallation of the coating.

The coating thus prepared is dense, forms an alumina scale when exposed to hot air, and adheres firmly to the tube. The plasma growing arc process may omit a separate aluminum plating step. The material transfer method is also very efficient and 80 to 90% of the raw material is incorporated into the coating, compared to 25 to 30% by magnetron sputtering.

Two high temperature alloy stainless steel materials were used as substrates: one is an H46M alloy and the other is a 900 B alloy. Coatings were obtained from NiCrAlY powders having 10 wt% Al, 22 wt% Cr, 1 wt% Y, nominal composition of the balance of Ni, and less than 1 wt% impurities. The size distribution of the powder was +45 microns -106 microns. The gun was fed across the arc at a rate of 30 grams per minute using 100 amps and 50 volts.

The coating was dense and continuous to a thickness of at least 4 mm with a smooth interface as shown in FIG. No defects were observed across the coating surface from the base alloy, but some bubbles were found near the outer surface of the coating. The composition reflected the fact that some of the alloy was melted, causing NiCrAlY to mix and dilute with the elements present in the HTA. In both cases, the aluminum content was 5 to 7% by weight. However, the samples deposited on H46M contained less iron and more nickel and chromium than the samples deposited on 900B. Some other elements present in the base alloy, such as silicon, niobium and manganese, were diffused into the coating, but none of the elements exceeded 1% by weight on the weld layer. No heat treatment was done before the inspection of these samples.

Samples were aged in air at 1150 ° C. for up to 500 hours. After each aging period, the samples were taken out of the oven and immersed in water to assess the overall thermal shock resistance. No sample fractured or cracked after this treatment. As shown in Figures 8 and 9, the bulk microstructure did not change significantly even after the aging period. However, new structures have been formed at free surfaces and interfaces. A 10 micron thick layer of aluminum was formed on the outer surface that proved to significantly reduce the formation of catalytic coke in the coated HTA alloy. In the voids and other internal defects, a core of mixed oxides (Cr-Al-Ni-Y O) precipitated inside the aluminum surface. Oxygen penetrated several microns inside the coating. At that interface, a large amount of nitride, basically AlN, was produced; These crystals were grown in a dispersed manner as shown in FIGS. 10 and 11. The number of nitrides was higher in the samples prepared on the high chromium H46M alloy, which is presumed to be due to the large amount of nitrogen dissolved inside the alloy. Even in this case, the nitrides did not aggregate linearly or continuously, and thus the mechanical Reduces the possibility of failure This avoids the need for the deposition of an interlayer whose main purpose is to absorb the nitrogen released from the tube. The amount of aluminum in the bulk, which was part of the original aluminum diffused into the base alloy, was reduced to just over 5% by weight after aging at 1150 ° C. for 500 hours.

This embodiment according to the method of the present invention provides a number of important advantages. The interfacial layer obtained by applying NiCrAlY powder to the substrate alloy by plasma growing arc is dense, continuous, flat, and metal-bonded with the HTA substrate. Precipitated nitrides and carbides are dispersed in and near the interfacial layer, which may eliminate the need for heat treatment of the coating and the provision of a separate interlayer. Sufficient aluminum is used in the coating to form the alumina surface scale. Aging in air at 1150 ° C. for 500 hours and evaluation of thermal shock resistance resulted in a slight change in composition and bulk structure. However, the nitride formed near the interfacial layer will disperse and eventually not appear as a delamination of the coating. The surface area showed oxidation, but the oxidation was thin and enough aluminum remained to maintain the protective alumina scale. The surface alloys on HTA according to the invention have a special use in the coating of reactor tubes for use in high temperature corrosive environments such as furnaces for ethylene production, for example.

The additive silicone may be present in an amount of 0 to about 40% by weight, preferably 3 to 15% by weight. The additive T may be present in an amount of 0 to 10% by weight, preferably 0.1 to 5% by weight, more preferably 0.5 to 3% by weight. Preferred additives T in MCrAlX consisting of about 12 to 25 wt% chromium, about 4 to 15 wt% aluminum, about 0.5 to 1.5 wt% yttrium, the balance nickel is titanium, tantalum, platinum or palladium, tungsten, molybdenum, Niobium or rhenium. Adding silicon to the MCrAlX coating improves high temperature corrosion resistance and oxidation resistance. The addition of tantalum and tungsten to the Cr-based coating improves sulfidation and oxidation resistance. The presence of molybdenum in the aluminum-forming alloy improves the quality of the Cr-based oxide scale that forms aluminum that has been removed from the coating alloy. The inclusion of titanium in the MCrAlX alloy composition improves coating resistance to high temperature corrosion, especially coating resistance to compounds containing sulfides and / or halides. The addition of niobium harmonizes with the thermal expansion of the substrate by reinforcing the coating and changing the coating thermal expansion coefficient. The presence of palladium, platinum or rhenium gives a good, slower growing alumina scale. Preferred compositions are MCrAlXSi comprising 22 weight percent Cr, 10 weight percent Al, 1 weight percent Y, 3 weight percent Si, balance nickel.

The thickness of the MCrAlXSi or MCrAlXT overlay coating is 20 to 6000 μm, preferably 50 to 2000 μm, more preferably 80 to 500 μm.

An aluminum surface layer, a surface layer of an aluminum alloy containing up to 50% by weight, preferably up to 15% by weight of silicon, or one of up to 60% by weight of silicon, up to 30% by weight of chromium and titanium, the balance being about 20% by weight An aluminum alloy surface layer containing at least% aluminum may be deposited on the MCrAlXSi or MCrAlXT coating in an amount up to 50% by weight of the coating thickness. Preferred top layers are aluminum layers or aluminum alloy layers having a thickness of 20% or less of the MCrAlSi or MCrAlXT overlay coating thickness.

Industrial embodiments of coatings according to the present invention are caulking and corrosion resistant reactor tubes for use in high temperature environments, including elongated tubes of high temperature stainless steel, and include physical vapor deposition, plasma thermal spraying or plasma grown arc surface treatment. From about 10 to 25 weight percent chromium, from about 4 to 20 weight percent aluminum, up to about 3 weight percent X, and up to about 8 weight percent T, deposited by one of several methods or applied by a binder coating, MCrAlXT alloy containing M as the remainder, wherein M is nickel, cobalt, iron or mixtures thereof, X is yttrium, hafnium, zirconium, lanthanum, scandium or combinations thereof, and T is silicon, tantalum, titanium, platinum, A continuous metal-bonded coating on the inner surface of the elongated tube comprising palladium, rhenium, molybdenum, tungsten, niobium, or a combination thereof, wherein the MCrAlXT coating is about 2 It has a thickness of 0-6000 micrometers.

MCrAlXSi coated silicon present in an amount of 3 to 40% by weight is added to the organic binder with a blending powder of two or more MCrAlXSi constituents to a substrate of carbon steel or low or high temperature stainless steel such as tubes and release tubes to form a slurry, and the substrate is It can be applied by coating with the slurry. The coated substrate is dried and heated in a vacuum furnace for evaporation of the organic binder and also for reaction sintering of the substrate and the coating for attaching the coating to the substrate.

Preferred slurry compositions include at least two powder components of MCrAlXSi where M is nickel. The powder is blended and added to an organic binder, such as an acrylic binder dissolved in an organic solvent. Nickel has a relatively small average size of 2 to 10 μm compared to the average size of the residual constituents or constituents 50 to 150 μm, and nickel has an irregular shape compared to the circular or spherical shape of the residual constituents or constituents. This change in size and shape causes the particles to interlock and remain on the substrate as the binder evaporates, as described below.

When 40 wt% or less of silicon is included in the blended powder, the melting point of the coating is lowered to about 900-1150 ° C. At a silicon concentration of 6% by weight or more, silicon dissolves the chromium carbide formed in the substrate, and when the silicon concentration drops to 6% by weight or less, silicon randomly reprecipitates carbide by diffusion into the substrate.

According to the subject matter of the present invention, by depositing two or more powders of the constituents of the MCrAlXSi alloy and coating the workpiece in a vacuum or oxygen-free atmosphere by heating the workpiece to a temperature for reactive sintering of the MCrAlXSi alloy and diffusion bonding of the alloy to the substrate. Five embodiments of surface alloy structures that can be produced are provided.

In the first embodiment of the present invention, two or more powders of the constituents of the MCrAlYSi alloy are blended together and isostatically pressed onto the workpiece surface. The workpiece with the pressed overlay coating is heated until reaction sintering occurs in a vacuum or oxygen-free atmosphere. In reaction sintering, it is necessary to balance the chemical activity of the components in order to avoid violent reactions. Once the coating is formed, the reaction must occur at a temperature at which adhesion of the coating to the substrate occurs. An example of an uncontrolled reaction is the formation of NiAl intermetallic compounds from Ni and Al powders. The temperature rises rapidly to about 1600 ° C., forming molten droplets of NiAl on the relatively cold substrate surface. These droplets solidify rapidly and do not react with the substrate due to the low substrate temperature and high chemical stability of NiAl. According to the invention, the activity of the powder is controlled to avoid violent reactions between the powders. Some constituents, such as Si and Al, are pre-reacted to lower the activity. For example, the micronized CrAlSi powder can be combined with a combination of Ni, NiAl and NiCr powders. This reduces the amount of heat generated during the reaction and allows the reaction to occur at higher temperatures. At high temperatures, the coating reacts with the substrate surface to form good coating / substrate bonds. It is necessary to add Si to the coating to form a low melting liquid (900-1000 ° C.) with Fe and Ni. These liquids wet the surface of the substrate and form a bond between the coating and the substrate. Si addition is also used to prevent brittle carbide formation at the coating / substrate interface. At initial concentrations above 6% by weight, Si dissolves the chromium carbide found in the substrate and randomly reprecipitates the chromium carbide because silicon diffuses into the substrate when the silicon concentration drops below 6% by weight.

In a second embodiment of the invention, two or more powders of the constituents of the MCrAlYSi-alloy are blended together and deposited as a coating on the workpiece surface by magnetron sputtering from thermal spraying, chemical vapor deposition or previously thermally sprayed anodes. . The coated workpiece is then heated until reaction sintering occurs in a vacuum or oxygen-free atmosphere.

In the third embodiment of the present invention, two or more powders of the constituents of the MCrAlYSi-alloy are blended together and deposited on the workpiece surface by a plasma growing arc process which performs a reaction sintering process simultaneously with deposition.

In a fourth embodiment of the invention, two or more powders of the constituents of the MCrAlYSi-alloy are combined with an effective amount of an organic binder and, if necessary, combined with a viscous transporting agent to deposit as a slurry on the workpiece surface. Mixed solvent. The workpiece is dried before heating in a vacuum or oxygen-free atmosphere until reaction sintering with overlay slurry coating occurs.

One of the advantages of the reactive sintering process is that no sharp dividing line is formed between the coating and the substrate. This not only produces better bonds between the coating and the substrate, but also results in a random distribution of brittle aluminum nitride in the case of the MCrAlY alloy on nitrogen containing the substrate. In MCrAlY coatings deposited by the PVD process, the nitride forms a brittle layer at the coating / substrate interface resulting in layer separation of the coating.

When heating the substrate, an oxygen-containing gas such as air is introduced at a temperature of about 1000 ° C. or higher at the end of heat soak as a continuous step and at a temperature of about 1000 ° C. or higher in an oxidizing gas atmosphere such as air in a separate step. By coating, or by the introduction or presence of an oxygen-containing gas at an operating temperature of about 1000 ° C. or higher during commercial use, the coating provides an aluminum source for providing a X-alumina based layer on its surface.

A fifth embodiment of the surface alloy structure according to the present invention includes depositing an aluminum layer on top of the MCrAlXSi surface alloy structure and heat treating the composition of the aluminum and MCrAlXSi surface alloyed substrate to form the desired coated microstructure. .

It is obvious that embodiments of the invention illustrated and described herein may be modified without departing from the scope and scope of the invention as defined in the appended claims.

Claims (100)

MCrAlX alloy deposited on a steel substrate and having from about 0 to 40% by weight of chromium, from about 3 to 40% by weight of aluminum and up to about 5.0% by weight of X, with a balance of M, wherein M is nickel, Non-catalytic surface to low-carbon steels and stainless steels, comprising metalbonding a continuous coating of cobalt or iron or mixtures thereof and X is yttrium, hafnium, zirconium, lanthanum, scandium, or a combination thereof A method of providing a protective coating having a. The method of claim 1 wherein the substrate is a high temperature stainless steel and the McrAlX alloy comprises about 10 to 25 weight percent chromium, about 5 to 20 weight percent aluminum and about 3 weight percent or less X, balance M Way. 3. The method of claim 2, wherein the coating and the substrate are metalbonded to the substrate by heat-treating to a aging temperature for a time effective to change the microstructure of the multi-phase and to bond the coating to the substrate. The method of claim 3, wherein X is present in an amount of 0.25 to 1.5 weight percent, the coating is deposited to a thickness of about 50 to 500 μm and the substrate is heated to ripening temperature in the range of about 1000 to 1200 ° C. How to keep at least about 10 minutes at temperature. The method of claim 4 wherein the MCrAlX is NiCrAlY, has about 12 to 22% by weight of chromium, about 8 to 20% by weight of aluminum and 0.8 to 1% by weight of yttrium, the balance of nickel, the coating is magnetron sputtering physical Depositing a thickness of about 50 to 350 μm on the substrate in a temperature range of about 200 to 1000 ° C. by vapor deposition. 5. The aluminum surface layer according to claim 4, wherein the aluminum surface layer has a thickness of about 50% or less of the coating, an aluminum alloy surface layer containing 50% or less of silicon, or 60% or less of silicon, up to 30% by weight of chromium and titanium. The surface layer is coated by depositing an aluminum alloy surface layer containing at least about 20% by weight aluminum in the coating, and heat-treating the coating together with the aluminum or aluminum alloy thereon and the substrate thereon at a aging temperature in an oxygen-free atmosphere. And metal bonding the coating overlay to the substrate, optionally heat treating in an oxidizing atmosphere to form an alumina surface scale thereon. 7. The aluminum alloy of claim 6, wherein the aluminum alloy contains up to 15% by weight of silicon and the aluminum or aluminum alloy is coated on the coating at about 20% of the coating thickness in a temperature range of about 200 to 500 DEG C by magnetron sputtering physical vapor deposition. Depositing and heat-treating for an effective time to form an alumina scale thereon in a temperature range of about 1000 ° C. to 1160 ° C. in an oxidizing atmosphere. 7. The method of claim 6, wherein a continuous layer is deposited on the stainless steel substrate prior to depositing the continuous MCrAlX coating to minimize or avoid formation of continuous nitride or carbide at the coating and substrate interface. And providing an interlayer of the method. The method of claim 8, wherein the interlayer comprises about 35 to 45 weight percent aluminum, about 5 to 20 weight percent chromium or titanium, and about 40 to 55 weight percent silicon, and 400 to 600 degrees Celsius. Or deposited to a thickness of about 20 to 100 μm on a high temperature stainless steel substrate at a temperature in the range of 800 to 900 ° C., wherein the interlayer is heat treated at a aging temperature in the range of 1030 to 1180 ° C. for at least about 20 minutes. The method of claim 9, wherein the stainless steel substrate contains about 31 to 38 weight percent chromium and the interlayer is heat treated at a aging temperature in the range of about 1130 to 1160 ° C. for about 30 minutes to 2 hours. The method of claim 9, wherein the stainless steel substrate contains about 20 to 25 weight percent chromium and the interlayer is heat treated at a aging temperature in the range of about 1050 to 1160 ° C. for about 30 minutes to 2 hours. 9. The high temperature stainless steel of claim 8, wherein the interlayer comprises about 35 to 45 weight percent aluminum, at least one of about 5 to 15 weight percent chromium or titanium, and about 50 to 55 weight percent silicon. A continuous MCrAlX alloy, wherein M is deposited on the substrate and has on the interlayer about 10-25 wt% chromium, about 6-15 wt% aluminum and about 3 wt% or less X, Nickel, cobalt or iron, or mixtures thereof, X is a yttrium, hafnium, lanthanum, scandium, or combination thereof), optionally depositing an aluminum layer on the MCrAlX alloy coating, A layer, a coating and an aluminum or aluminum alloy surface layer are used to diffuse the surface layer into the coating at a aging temperature in an oxygen free atmosphere and to provide a multi-phase microstructure and interlayer with the coating. Heat treatment for an effective time to metal bond to the substrate, and then heat treatment for an effective time to form an alumina surface scale thereon in an oxidizing atmosphere of about 1000 ° C. or more in some cases. 13. The method of claim 12, wherein the coating and substrate are heated for about 20 minutes to 24 hours to a aging temperature in the range of about 1030 to 1180 ° C. 13. The method of claim 12, wherein the interlayer is deposited by magnetron sputtering physical vapor deposition in the temperature range of 800 to 900 ° C, wherein the MCrAlX coating and substrate having the interlayer, aluminum or aluminum alloy surface layer are heated at a rate of 5 ° C / min or more. Heated to aging temperature. 15. The method of claim 14, wherein the MCrAlX coating with the interlayer, aluminum or aluminum alloy surface layer and the substrate are heated to a aging temperature at an elevated rate of 10 to 20 [deg.] C./min. The method of claim 15, wherein the interlayer is deposited to a thickness of about 20 to 100 μm, and the MCrAlX coating and substrate base alloy with the interlayer, aluminum or aluminum alloy surface layer is a base at a aging temperature in the range of about 1030 to 1160 ° C. 17. A method of heat treatment for an effective time to form an interlayer between an alloy and a concentrated pool containing an intermetallic compound of silicon and one or more titanium or aluminum and base alloy elements. 17. The method of claim 16 wherein the interlayer comprises about 6 to 10 weight percent silicon, 0 to 5 weight percent aluminum, 0 to 4 weight percent titanium and about 25 to 50 weight percent chromium, balance iron and A method containing nickel and other base alloy elements. The method of claim 17, wherein the stainless steel substrate contains about 31 to 38 weight percent chromium and the interlayer is heat treated at a aging temperature in the range of about 1130 to 1160 ° C. for about 30 minutes to 2 hours. 18. The method of claim 17, wherein the stainless steel substrate contains about 20 to 25 weight percent chromium and the interlayer is heat treated at a aging temperature in the range of about 1050 to 1160 ° C for about 30 minutes to 2 hours. About 10-25 wt% chromium, about 5-20 wt% aluminum and about 3 wt% or less of yttrium, hafnium, lanthanum, scandium, or the like, comprising a stainless steel base alloy substrate and a continuous coating deposited thereon MCrAlX alloy having a balance of M, the balance of M, and heat treated at a temperature effective to metal bond to the substrate and provide a microstructure of the multiphase, wherein M is nickel, cobalt, iron or mixtures thereof, and X is yttrium, hafnium , Lanthanum, scandium, or a combination thereof. 21. The surface alloyed component of claim 20, wherein X is present in an amount of 0.25 to 1.5 weight percent and the coating and substrate are heated at a aging temperature in the range of about 1000 to 1180 ° C for about 20 minutes to 24 hours. 22. The surface alloyed component of claim 21 wherein the MCrAlX is about 12-22 weight percent chromium, about 8-13 weight percent aluminum, about 0.8-1 weight percent yttrium, and NiCrAlY, the balance being substantially nickel. . 22. The surface alloyed component of claim 21 wherein the coating is deposited on the stainless steel substrate by magnetron sputtering. The surface alloyed component of claim 23 wherein the coating has a thickness of about 50 to 350 μm. 22. An aluminum surface layer as claimed in claim 21 having a thickness of about 50% of the coating thickness, an aluminum alloy surface layer containing up to 50 wt% silicon, or up to 60 wt% silicon, up to 30 wt% total. At least one of chromium and titanium, the surface alloy treated component further comprising an aluminum alloy surface layer containing aluminum having a balance of about 20% by weight or less. 26. The method of claim 25, wherein the aluminum or aluminum alloy surface layer is deposited on the coating by magnetron sputtering to a thickness of about 20% or less of the coating thickness and to form a protective alumina scale thereon at a temperature of about 1000 ° C. or higher in an oxidizing atmosphere. Surface alloyed components oxidized for valid time. 21. The surface of claim 20, further comprising an interlayer deposited on the substrate between the substrate and the coating, the interlayer being metal bonded to the substrate and the coating effective to minimize or avoid the formation of continuous nitrides or carbides at the coating and the substrate surface. Alloyed components. The method of claim 27 wherein the interlayer has a thickness of about 20 to 100 μm and comprises about 35 to 45 weight percent aluminum, about 5 to 15 weight percent titanium or chromium, and about 45 to 55 weight percent silicon. Surface alloy treated components comprising. The method of claim 20, having a thickness of about 20-100 μm, deposited on the substrate between the substrate and the MCrAlX coating, about 50 wt% chromium and about 50 wt% nickel or about 20 wt% titanium, The surface alloy treated component further comprising an interlayer having 20% by weight of aluminum and the balance of silicon. The surface alloyed component of claim 28 wherein the interlayer has a thickness of about 20 to 60 μm prior to heat treatment. 29. The surface alloyed component of claim 28 wherein the interlayer has a diffusion barrier between a stainless steel substrate and a coating containing silicon and an intermetallic compound of one or more titanium or aluminum and base alloy elements after heat treatment. 31. The method of claim 30, wherein the interlayer is subjected to heat treatment of stainless steel and about 6 to 10 weight percent silicon, 0 to 5 weight percent aluminum, 0 to 4 weight percent titanium and about 25 to 50 weight percent chromium, balance of A surface alloyed component having a diffusion barrier between the coating containing iron and nickel and other base alloy elements. In a coking and corrosion resistant reactor tube or release tube for use in high temperature environments, a high temperature stainless steel alloy and about 10 to 25% chromium, about 5 to 20% aluminum and up to about 3% yttrium, Extensions comprising hafnium, zircon, lanthanum or scandium, remaining amounts of MCrAlX alloy, where M is Ni, Co, Fe or mixtures thereof and X is yttrium, hafnium, lanthanum, scandium or combinations thereof An elongated tube or release tube formed from a continuous coating deposited on the inner surface of the drawn tube or release tube, wherein the MCrAlX alloy coating is metal-bonded to the inner surface of the extended tube or release tube and a multiphase microstructure is provided to the MCrAlX alloy coating. Caulking and corrosion resistant reactor tubes or release tubes that are heat treated at an effective temperature. 34. The composition of claim 33, which is at least one of an aluminum surface layer, an aluminum alloy surface layer containing up to 50 weight percent silicon, or up to 60 weight percent silicon, up to 30 weight percent chromium and titanium, remaining at least about 20 weight percent. A caulking and corrosion resistant reactor tube or release tube further comprising an aluminum alloy surface layer containing aluminum, having a thickness of about 50% or less of the coating thickness and metal bonded to the coating, the protective alumina scale thereon. 35. The composition of claim 33, wherein about 35 to 45 weight percent aluminum is deposited on the inner surface of the elongated tube or release tube as an interlayer between the stainless steel substrate and the coating and metal bonded to the inner surface of the elongated tube and coating. A caulking and corrosion resistant reactor tube or release tube further comprising an interlayer having 5 to 15 weight percent chromium or titanium, and about 45 to 55 weight percent silicon. 36. The caulking and corrosion resistant reactor tube or release tube of claim 35, wherein the interlayer has a thickness of about 20 to 100 microns prior to heat treatment. 37. The reactor or release tube of claim 36 wherein said interlayer has a diffusion barrier between a stainless steel substrate and a concentration pool containing silicon and intermetallic compounds of one or more titanium or aluminum and base alloy elements. . 37. The method of claim 36 wherein the interlayer is stainless steel and about 6 to 10 weight percent silicon, 0 to 5 weight percent aluminum, 0 to 4 weight percent titanium and about 25 to 50 weight percent chromium, balance iron And a caulking and corrosion resistant reactor tube or release tube having a diffusion barrier between the coating containing nickel and other base alloy elements. Caulking and corrosion resistant reactor tubes or release tubes made by the process according to claim 4. A caulking and corrosion resistant reactor tube or release tube produced by the process according to claim 7. A caulking and corrosion resistant reactor tube or release tube produced by the process according to claim 16. Each reactor tube is a high temperature stainless steel alloy and about 10-25 wt% chromium, about 5-20 wt% aluminum and about 0.25-1.5 wt% yttrium, hafnium, zircon, lanthanum, scandium or combinations thereof, balance A continuous deposited on the inner surface of an elongated tube comprising an MCrAlX alloy with M, wherein M is Ni, Co, Fe or a mixture thereof and X is yttrium, hafnium, lanthanum, scandium or a combination thereof An ethylene comprising a plurality of reactor tubes heat treated at a temperature effective to extend the tube formed from the conventional coating and to metal bond the MCrAlX alloy overlay to the inner surface of the extended tube and provide the multiphase microstructure to the MCrAlX alloy overlay. Into production. 43. The reactor of claim 42 wherein each reactor tube is at least one of an aluminum surface layer, an aluminum alloy surface layer containing up to 50 weight percent silicon, or up to 60 weight percent silicon, up to 30 weight percent chromium and titanium, with a balance remaining. A furnace containing at least 20% by weight aluminum, having a thickness of 50% or less of the coating thickness, and further comprising an aluminum alloy surface layer metal-bonded to the MCrAlX coating, the alumina scale thereon. 44. The reactor of claim 43 wherein each reactor tube has a thickness of about 20 to 100 micrometers and comprises about 35 to 45 weight percent aluminum, about 5 to 15 weight percent titanium, and about 45 to 55 weight percent silicon. And an interlayer deposited on the inner surface of the tube extending between the stainless steel substrate and the coating and metal-bonded to the inner surface of the extended tube and the coating. Plasma-grown arc deposition of a coating on a high temperature stainless steel substrate to provide an MCrAlX alloy having from about 0 to 40% by weight of chromium, from about 3 to 30% by weight of aluminum and up to about 5% by weight of X, with a balance of M, wherein M Silver nickel, cobalt or iron, or mixtures thereof, wherein X is a metal coating of a continuous coating of yttrium, hafnium, lanthanum, scandium, or a combination thereof) to provide a protective and inert coating to hot stainless steel. Way. 46. The method of claim 45, wherein the MCrAlX alloy has about 10-25 weight percent chromium, 4-20 weight percent aluminum, and 3 weight percent or less. 46. The method of claim 45, wherein the coating is deposited on the substrate to a thickness of about 20 to 6000 microns. 48. The method of claim 47, wherein the coating is deposited to a thickness of about 50 to 2000 micrometers and X is present in an amount of 0.25 to 1.5 weight percent. 48. The method of claim 47, wherein the coating is deposited to a thickness of about 80-500 μm. 46. The method of claim 45, wherein the MCrAlX is 0-25 wt% chromium, about 3-40 wt% aluminum, up to about 3 wt% yttrium, and FeCrAlY having substantially iron as balance. 49. The method of claim 48, wherein said MCrAlX is NiCrAlY and has about 12-25 weight percent chromium, about 4-15 weight percent aluminum and about 0.5-1.5 weight percent yttrium, balance nickel. 48. The method of claim 47, wherein the coating comprises an aluminum surface layer having a thickness of about 50% of the coating thickness, an aluminum alloy surface layer containing up to 50% by weight of silicon, or up to 60% by weight of silicon, up to 30% by weight of chromium. And depositing an aluminum alloy surface layer containing at least one of titanium, the balance being at least about 20% aluminum by weight, and heat treating the substrate and the substrate with aluminum thereon to diffuse aluminum into the coating. 53. The method of claim 52, wherein the aluminum or aluminum alloy layer has a thickness of about 20% or less of the coating thickness deposited on the coating. MCrAlX alloy comprising stainless steel base alloy substrate and about 0-40 wt% chromium, about 3-30 wt% aluminum and about 5 wt% or less of yttrium, hafnium, zircon, lanthanum or combinations thereof, balance M Wherein M is nickel, cobalt, iron, or mixtures thereof, and X is yttrium, hafnium, lanthanum, scandium, or a combination thereof; and a continuous coating deposited thereon by plasma grown arc deposition, wherein The MCrAlX alloy coating has a thickness of about 20 to 6000 μm, and the surface alloyed component is metal bonded to the stainless steel substrate. 55. The surface alloyed component of claim 54 comprising a stainless steel substrate and an MCrAlX alloy having about 4 to 20 weight percent aluminum, 10 to 25 weight percent chromium and up to 3 weight percent X. 56. The surface alloyed component of claim 55 wherein X is present in an amount from 0.25 to 1.5 weight percent. 59. The surface alloy treated of claim 56 wherein MCrAlX is about 12-25 wt% chromium, about 4-15 wt% aluminum, about 0.5-1.5 wt% yttrium, and NiCrAlY containing substantially nickel as balance. ingredient. 56. The surface alloyed component of claim 55 wherein the coating has a thickness of about 80-500 μm. 59. The surface alloyed component of claim 58 further comprising an aluminum surface layer having a thickness of about 50% or less of the coating thickness and metallicly bonded to the coating. 60. The surface alloyed component of claim 59 wherein the aluminum surface layer has a thickness of about 20% of the coating thickness and has a protective alumina scale thereon. 55. The surface alloyed component of claim 54 wherein MCrAlX is about 0-25 wt% chromium, about 3-40 wt% aluminum, up to about 3 wt% yttrium, and FeCrAlY containing substantially iron as balance. . MCrAlX alloys having a high temperature stainless steel alloy and about 10-25 wt% chromium, about 4-20 wt% aluminum, and up to about 3 wt% yttrium, hafnium, zircon, lanthanum or scandium, or a combination thereof, wherein M Silver, Ni, Co, Fe, or mixtures thereof, wherein X is yttrium, hafnium, lanthanum, scandium, or a combination thereof) from a metal-bonded continuous coating by plasma growing arc deposition on the inner surface of the elongated tube. And an elongated tube formed, wherein the MCrAlX coating has a thickness of about 20-6000 μm and is metal bonded to a stainless steel substrate. An MCrAlX alloy having a high temperature stainless steel alloy and about 0-25 wt% chromium, about 3-40 wt% aluminum, and up to about 3 wt% yttrium, wherein M is iron and y is yttrium A coating comprising an extended tube formed from a continuous coating of metal bonds by plasma-growing arc deposition on the inner surface of the extended tube, wherein the MCrAlX coating has a thickness of about 20-6000 μm and is metal bonded to a stainless steel substrate; Caulking and corrosion resistant reactor tubes for use in high temperature environments. 58. A coking and corrosion resistant reactor tube as recited in claim 57, further comprising an aluminum surface layer having a thickness of 20% or less of the coating thickness and metal bonded to the coating and having an alumina scale thereon. A caulking and corrosion resistant reactor tube made by the process according to claim 48. A caulking and corrosion resistant reactor tube made by the process according to claim 51. A caulking and corrosion resistant reactor tube made by the process according to claim 53. Each reactor tube has high temperature stainless steel and about 10 to 40 weight percent chromium, about 3 to 30 weight percent aluminum and up to 5 weight percent yttrium, hafnium, zircon and / or lanthanum, balance M, about 20 MCrAlX alloys deposited to a thickness of from about 6000 μm and metal bonded to the inner surface of the tube extended by the plasma grown arc deposition method, wherein M is Ni, Co, Fe, or a mixture thereof, and X is yttrium, hafnium, zircon Ethylene production furnace comprising a plurality of reactor tubes comprising an elongated tube formed from a continuous coating of lanthanum, scandium or a combination thereof. 69. The reactor of claim 68, wherein each reactor tube is at least one of an aluminum surface layer, an aluminum alloy surface layer containing up to 50 weight percent silicon, or up to 60 weight percent silicon, up to 30 weight percent chromium and titanium, with a balance of about A furnace containing at least 20% by weight aluminum, having a thickness of 50% or less of the coating thickness, and further comprising an aluminum alloy surface layer metal-bonded to the MCrAlX coating, the alumina scale thereon. 69. The furnace of claim 68, wherein MCrAlX is NiCrAlY with about 10-25 wt% chromium, about 4-20 wt% aluminum and about 0.5-1.5 wt% yttrium, balance nickel. The method of claim 1 wherein MCrAlX further comprises up to about 40 weight percent silicon and up to about 10 weight percent T element selected from tantalum, titanium, platinum, palladium, rhenium, molybdenum, tungsten, niobium, or combinations thereof And heat treating the coating and the substrate to a aging temperature for a time effective for changing the microstructure of the multi-phase and for bonding the coating to the substrate. High temperature stainless steel substrate tube and about 0-40 wt% chromium, about 1-30 wt% aluminum, about 5 wt% or less X, about 40 wt% or less silicon, and about 10 wt% or less T, balance MCrAlXSiT alloy with M, wherein M is nickel, cobalt, iron or mixtures thereof, X is yttrium, hafnium, zircon, lanthanum, scandium or mixtures thereof, and T is tantalum, titanium, platinum, palladium, rhenium , Molybdenum, tungsten, niobium, or a combination thereof. 73. The surface of claim 72, wherein the MCrAlXSiT alloy has about 10-25 wt% chromium, 5-20 wt% aluminum, 3 wt% or less X, 15 wt% or less silicon, and 10 wt% or less T. Alloyed components. 74. The surface alloyed component of claim 73 wherein X is present in an amount from 0.25 to 1.5 weight percent. 74. The surface alloyed component of claim 73 wherein the silicone is present in an amount of about 3 to 15 weight percent. 74. The surface alloyed component of claim 73 wherein T is present in an amount from 0.1 to 5.0 weight percent. 74. The surface alloyed component of claim 73 wherein T is present in an amount from 0.5 to 3.0 weight percent. 73. The surface alloyed component of claim 72 wherein the coating has a thickness of 20 microns to 6000 microns. 73. The surface alloyed component of claim 72 wherein the coating has a thickness of 50 microns to 2000 microns. 73. The surface alloyed component of claim 72 wherein the coating has a thickness of 80 μm to 500 μm. 73. The method of claim 72, wherein the MCrAlXSiT alloy is NiCrAlXSi, wherein about 12-25 weight percent chromium, about 4-15 weight percent aluminum, about 0.5-1.5 weight percent X, about 15 weight percent silicon and the balance nickel Surface alloy treated component having a. 74. The method of claim 73 wherein MCrAlXSiT is NiCrAlXTi, wherein about 12-25 weight percent chromium, about 4-15 weight percent aluminum, about 0.5-1.5 weight percent yttrium, about 5 weight percent or less titanium and the balance nickel Having surface alloy treated components. 74. The method of claim 73, wherein MCrAlXSiT is NiCrAlYTa, wherein about 12-25 weight percent chromium, about 4-15 weight percent aluminum, about 0.5-1.5 weight percent yttrium, about 0.5-5 weight percent tantalum and balance nickel Surface alloy treated component having a. 74. The method of claim 73, wherein MCrAlXSiT is NiCrAlYPt and comprises about 12-25 weight percent chromium, about 4-15 weight percent aluminum, about 0.5-1.5 weight percent yttrium, about 0.5-5 weight percent platinum and balance nickel. Surface alloy treated component having a. 74. The method of claim 73, wherein MCrAlXSiT is NiCrAlYPd and comprises about 12-25 wt% chromium, about 4-15 wt% aluminum, about 0.5-1.5 wt% yttrium, about 0.5-5 wt% palladium and the balance nickel Surface alloy treated component having a. 74. The surface alloyed component of claim 73 further comprising a surface layer that is about 50% or less thick of the MCrAlXSiT layer thickness. 85. The surface alloyed component of claim 84 wherein the aluminum alloy contains up to about 15 weight percent silicon and has a thickness of up to 20% of an MCrAlXSiT coating. MCrAlXSiT with high temperature stainless steel and about 10-25 wt% chromium, about 4-20 wt% aluminum and about 3 wt% or less X, 15 wt% or less silicon and about 5 wt% or less T, balance M Coating, wherein M is nickel, cobalt, iron or mixtures thereof, X is yttrium, hafnium, zircon, lanthanum, scandium or combinations thereof, T is tantalum, titanium, platinum, palladium, rhenium, molybdenum, tungsten, An elongated tube of continuous coating metal-bonded by physical vapor deposition, plasma spraying, or plasma-grown arc surfacing on the inner surface of the elongated tube), wherein the MCrAlXSiT coating comprises about 20 A caulking and corrosion resistant reactor tube for use in high temperature environments having a thickness of from about 6000 μm. Deposited on a steel substrate, wherein about 0-40% by weight of chromium, about 3-40% by weight of aluminum, about 0-35% by weight of silicon and about 5.0% by weight or less of X, remainder, about 40% by weight Metal bonding a continuous coating of MCrAlXSi alloys having M or more, wherein M is nickel, cobalt or iron, or mixtures thereof, X is yttrium, hafnium, zirconium, lanthanum, scandium, or a combination thereof To provide a protective and inert coating on the carbon steel. 90. The method of claim 89, wherein the coating is deposited by physical vapor deposition, thermal spraying, plasma growing arc, welding overlay, isotropic pressing, and slurry coating. 90. The method of claim 89, wherein the coating consists of at least two powders of the constituents of MCrAlXSi, partially prealloyed and blended together, deposited on a substrate, and to a temperature of 500 to about 1200 ° C. in a vacuum or oxygen-free atmosphere. Heated for a time effective to initiate reactive sintering and metal bond the coating as a continuous impermeable coating to the substrate. 92. The method of claim 91, wherein the coating is deposited to a thickness of about 50 to 6000 micrometers and the MCrAlXSi coating is substantially from about 0 to 20 weight percent chromium, about 4 to 20 weight percent aluminum, about 5 to 20 weight percent Silicon, and from about 0.25 to 1.5 weight percent yttrium, with at least 40 weight percent nickel remaining. 93. The method of claim 92, wherein the substrate is high chromium stainless steel with 18 to 38 weight percent chromium, 18 to 48 weight percent nickel, balance iron and alloying additives, and the coating is about 120 to 500 μm thick. How to be deposited. 94. The method of claim 93, wherein the coating is deposited to a thickness of about 150 to 350 microns. 95. The method of claim 94, wherein at least 10 minutes effective for depositing an aluminum layer having a thickness of about 50% or less of the MCrAlXSi coating to the coating and forming the multi-phase structure at a aging temperature in the range of about 1000 to 1160 ° C. The coating is aluminum plated by heat treatment during the process. 96. The method of claim 95, wherein the aluminum layer is deposited to a thickness of about 20% of the MCrAlXSi coating in a temperature range of about 200 to 500 ° C. by magnetron sputtering physical vapor deposition. 92. The method of claim 91, wherein the substrate, MCrAlYSi coating and aluminum layer are sequentially heated for a time effective to form an alumina layer thereon at a temperature in the range of 1000 to 1160 ° C. in an oxygen-containing atmosphere. 92. The method of claim 91, wherein chromium, aluminum, and silicon are micronized to form CrAlSi powders prior to blending with nickel, NiCr or NiAl powders, or combinations thereof. A surface alloyed component prepared by the method according to claim 89. A surface alloyed component produced by the method according to claim 92.