JPS6331546B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD This invention relates to abrasion and corrosion resistant coatings and methods of making the same. More particularly, the present invention relates to a new W--Co--Cr--C coating system with improved strength and abrasion resistance.

BACKGROUND ART W--Co--Cr--C coatings are used in applications that require both excellent wear resistance and corrosion resistance. Typical compositions for these coatings include about 8-10% by weight cobalt, about 3-4% by weight chromium, about 4.5-5.5% by weight carbon;
and the remaining tungsten. These coatings can be applied to a variety of substrates, such as iron-based alloy substrates, using well-known thermal spray techniques with good results. Such techniques are described, for example, in U.S. Pat. No. 2,714,563 and
Detonation gun (D) disclosed in No. 2950867
- Gun) Adhesion, U.S. Patent Nos. 2,858,411 and 3,016,447
and other so-called "velocity" plasma or "ultravelocity" combustion spraying processes.

Although W-Co-Cr-C coatings have been used with good results in many industrial applications over the past decade or more, there are even better coatings with excellent strength and wear resistance. The demands on coatings are ever increasing.

It is also desirable to deposit these coatings at faster deposition rates than are conventionally possible, thereby making the substrate more economical to apply.
However, a problem with fast deposition rates was that high residual stresses tended to build up within the coating. If the coating does not have high enough strength to withstand these stresses, it will crack and even fracture.

J. E., J. Jackson, filed on the same date as this application and assigned to a common assignee with this application.
Co-pending U.S. Pat. These coatings are ideally suited for use in gate valves handling highly corrosive fluids under high hydraulic pressure, for example in the petrochemical industry. Although these coatings are sufficiently tough and strong to withstand the high residual stresses that occur as a result of fast deposition rates, the abrasion resistance of the coatings is only that of conventional coatings.

As commonly known, W-Co-Cr-C
The coating derives its wear resistance from the presence of a composite carbide of W, Co, and Cr. On the other hand, corrosion resistance is derived from the presence of chromium. In practice, the chromium content is a compromise between the amount normally required for corrosion resistance and the amount that impairs or reduces the wear resistance and mechanical properties of the coating.

SUMMARY OF THE INVENTION In accordance with the present invention, it has been surprisingly and unexpectedly demonstrated that if higher chromium contents are used in proper balance with carbon and cobalt contents, the wear rate is lower and the deposition rate is progressively higher. It has now been found that it is possible to achieve improved coatings that can be applied without cracking or spalling.

The coating composition according to the invention essentially comprises:
About 4.0 to about 10.5% by weight of cobalt and about 5.0 to about chromium
about 11.5% by weight, about 3.0 to about 5.0% by weight carbon, and the balance tungsten.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The coatings of the present invention can be applied to a substrate using any conventional thermal spraying technique. The preferred method of applying the coating is by detonation gun (D-gun) deposition.
A typical D-gun essentially consists of a water-cooled barrel several feet long and about 1 inch (2.5 cm) inside diameter. In practice, a mixture of oxygen and a fuel gas, such as acetylene, in a specific ratio (usually about 1:1) is fed into the barrel along with the charge of powder to be applied. Then, when the gas is ignited, a detonation wave accelerates the powder to approximately 2400 ft/sec (730 m/sec),
Moreover, the powder is heated near or above its melting point.
After the powder exits the barrel, a pulse of nitrogen purges the barrel and prepares the system for the next datenation. The cycle is then repeated several times per second.

The D-gun deposits a circle of coating on the support for each detonation. The circle of coating is approximately 1 inch (25 mm) in diameter and a few ten thousandths of an inch (micron) thick. Each circle of coating consists of a number of overlapping fine splats corresponding to individual powder particles. The overlapping plates interlock and mechanically bond to each other and to the support so that they do not substantially alloy at their interfaces. The placement of the circles in the coating deposition is tightly controlled to deposit a smooth coating of uniform thickness and to minimize substrate heating and residual stress in the applied coating.

The powders used to make the coatings of the present invention are selected to achieve the desired specific coating composition with a predetermined set of deposition parameters. Preferably, the oxygen-fuel gas mixture ratio used in the D-gun process is maintained at about 1.0. D
- It is also possible to use other operating conditions for the gun and, if the powder composition is further adjusted accordingly, to obtain the desired coating composition. Additionally, other powder compositions can be used in other thermal spray application equipment to compensate for compositional changes during deposition to obtain the desired coating compositions of the present invention.

The powders used in the D-gun for applying coatings in accordance with the present invention are preferably cast and crushed powders. However, other powder forms can also be used, for example sintered powders. Typically, the powder size should be approximately -325 mesh. Powders produced by other manufacturing methods and having other size distributions may be deposited using other thermal spray deposition techniques if the powders are more suitable for the particular spray equipment and/or size. can be used according to the invention.

A typical powder composition for depositing a coating in accordance with the present invention will consist essentially of about 8.0 to about 8.0 cobalt.
11.0% by weight, about 8.0 to about 11.0% by weight chromium, about 4.0 to about 5.5% by weight carbon, and the balance tungsten. A certain amount of carbon, e.g. about 1.0
There may be up to % by weight of unbound carbon, which may be lost in the deposition process. The feed rates of both oxygen and fuel gas (eg, acetylene) should be matched to this powder to give an oxy-fuel gas ratio of about 1.0. This is the same ratio that has been used to deposit conventional coatings of the prior art.

Alternatively, the coating of the present invention can be applied to the substrate by plasma arc spraying or other thermal spraying techniques. In a plasma arc spraying process, an electric arc is established between a non-consumable electrode and a spaced apart second non-consumable electrode. The gas is passed in contact with a non-consumable electrode such that the gas contains an arc. The arc-containing gas is throttled by a nozzle into an effluent stream with a high heat content. The powder coating material is deposited onto the surface to be coated by injecting it into a high heat content effluent nozzle. This process, described in the above-mentioned US Pat. No. 2,858,411, creates a strong, dense, substrate-adhesive coating. Application coatings also consist of irregularly shaped fine plates or flakes that are interlocked and mechanically bonded to each other and to a support.

In those cases where a plasma arc spray process is used to apply the coating in the present invention, the powder fed to the arc torch may have essentially the same composition as the applied coating itself. However, in the case of certain plasma arc or other thermal spray equipment, some change in composition is expected and in such cases the powder composition may be adjusted accordingly to form the coating composition of the present invention. can be achieved.

The coating of the invention can be applied to almost any type of support, e.g. metal supports such as iron or steel;
Alternatively, it can be applied to a non-metallic support such as carbon, graphite or polymer. Some examples of support materials suitable for use in various environments and as supports for the coatings of the present invention include, for example, steel, stainless steel, iron-based alloys, nickel, nickel-based alloys,
Includes cobalt, cobalt-based alloys, chromium, chromium-based alloys, titanium, titanium-based alloys, aluminum, aluminum-based alloys, copper, copper-based alloys, heat-resistant metals, and heat-resistant metal-based alloys.

Although the composition of the coating of the present invention can vary within the ranges indicated above, a preferred coating composition consists essentially of about 5.5 to about 7.5% by weight cobalt;
About 5.5 to about 7.5% chromium by weight and about 3.0 to about 5.0% carbon
% by weight and the remainder tungsten. In the practice of this invention, the ratio of cobalt to chromium is preferably about 1:1.

The microstructure of the coating of the present invention is extremely complex and not completely understood. However, some of the major and minor phases of both powders and coating compositions can be analyzed essentially using three techniques: (1) X-ray diffraction, (2) metallography, and (3) scanning electron microscopy. Identification was made using an examination method (SEM). X-ray diffraction identifies the phases and provides an estimate of their volume. However, some of the phases present in small amounts are not observed by X-ray diffraction. The following phases were identified by X-ray diffraction: Powder Main: W ₂ C Small: Hexahedral WC, CoW ₃ C Coating Main: W ₂ C Small: Cubic WC The coating of the present invention is different from the conventional coatings of the prior art. exhibits both improved strength and abrasion resistance compared to Because of its improved strength, the coating of the present invention can withstand highly corrosive fluids (e.g., solutions containing chlorides, carbon monoxide, carbon dioxide, hydrogen sulfide, panadium salts, etc.) under moderately high hydraulic pressures.
Typically about 10000psi (700Kg/cm ² ), and 200〓
It is ideally suited for use in gate valves used in well service equipment that handle temperatures above (93°C). Previously, conventional coatings were ineffective under these conditions, often due to their relatively low tensile strength.

The mechanism of these failures is believed to be as follows: At high pressures and sufficiently high temperatures, the pressurized fluid slowly diffuses through the thickness of the coating and accumulates within the pores of the coating. During this stage, the coating is in compression and resists ambient pressure very well. After a predetermined time, the pressure within the pores reaches a value equal to ambient pressure and the inward diffusion of fluid ceases. As long as the pressure is maintained, the coating will not experience any abnormal pressure.

However, once ambient pressure is released, the pressure within the pores no longer balances with ambient pressure. Before the pressurized fluid within the pores has diffused out of the coating, the coating is stressed or loaded from within itself. If the specified load inside the coating exceeds the breaking stress of the coating, the coating will fail outwardly from within the coating.

In order to meet the stringent requirements for gate valves subjected to high pressures and temperatures, it is imperative to provide an even stronger coating while retaining all the usual requirements for gate valve coatings, such as wear resistance and corrosion resistance. .

Typically, coatings containing tungsten carbide, cobalt or nickel, chromium exhibit low resistance to failure of the types described above, and low resistance when hydraulically loaded outward from the interface. It showed strength. However, these coatings have shown good wear and corrosion resistance. On the other hand, coatings containing tungsten carbide and cobalt but without chromium have shown good fracture resistance and high strength when subjected to high internal pressures. However, these coatings provide little or no corrosion resistance due to the lack of chromium. Adding chromium to the coating can increase corrosion resistance, but at the cost of reducing the strength of the coating to the point of failure when the coating is subjected to high internal pressures.

The coating of the present invention represents a significant and unexpected improvement over the prior art. The coating not only incorporates sufficient chromium to impart corrosion resistance, but also incorporates sufficient cobalt, tungsten, and carbon in appropriate relative proportions to provide a 50% improvement in toughness and strength over conventional coatings; At the same time, it greatly increases wear resistance. Although the exact reasons for the improved strength and abrasion resistance are not clearly understood, it is believed that the improved strength and abrasion resistance result from chemical changes and associated phase changes within the coating.

In addition to improved strength and abrasion resistance, the present invention provides the advantage that coatings can be applied to substrates at faster deposition rates than previously possible without deep cracking or spalling.
This is naturally made possible by the coating of the present invention having sufficient strength to withstand the high residual stress build-up that occurs when the coating is deposited at high rates. Using high deposition rates considerably reduces the cost of manufacturing the coating because it requires less equipment and operator time.

Another advantage of the present invention is that the coating exhibits a smooth "as-stick" surface, which requires less abrasion to finish the coating compared to prior art coatings. In other words, the coatings of the present invention require less coating material to be deposited on the substrate to achieve the same finished coating surface and thickness as prior art coatings, while reducing abrasion and corrosion resistant coating requirements. I won't let you. On top of that,
Because less coating material is required to deposit, the coating process is much more efficient and less expensive than prior art processes.

The following examples serve to further illustrate the implementation of the invention.

EXAMPLE AISI 1018 steel specimens were cleaned and prepared for the following coating: One surface of each specimen was ground smooth and parallel to the opposite side. The surface was then grit blasted with 60 meshes of Al ₂ O ₃ to give a surface roughness of approximately 120 microinches RMS. These specimens were set aside and prepared for the hydraulic test as follows: on the side to be coated,
Eight small 0.020 inch (0.51 mm) holes are drilled into the specimen support, perpendicular to the surface, a few tenths of an inch (a few tenths of an inch) apart.
It was drilled to a depth of mm). The hole was then enlarged to accommodate a leak-tight coupling. A 0.020 inch (0.51 mm) diameter piano wire is then inserted through the coupler into the small hole and clamped so that the ends of the piano wire are uniform and provide a smooth connection with the surface to be coated. Tightened. All specimens were then applied by conventional techniques using a detonation gun (D-gun) and a sintered powder of the following composition: Co10
Weight%, Cr4wt%, C5.2wt%, remainder W. The powder size was approximately -325 mesh. Acetylene was used as the fuel gas. The oxy-fuel gas ratio was 0.98. The feed rate was 75 grams/minute.

Chemical analysis of the coating showed the following composition: 8% by weight Co, 3.2% by weight Cr, 4.7% by weight C, balance W. Chemical analysis was performed mainly by two methods. Carbon was analyzed by combustion analysis techniques using a Leco carbon analyzer and volumetric determination of gaseous production. Cobalt and chromium were analyzed by first separating the cobalt and chromium by melting the sample in Na ₂ O ₂ and then quantifying the amount of each potentiometrically.

The mechanical strength of the coating was determined by a hydraulic test as follows: after applying the sample prepared for this test in the manner described above, the piano wire was carefully removed and a hole (cavity) was placed just below the coating. gave. The hole was then connected to the hydraulic system by a coupler, and the hole was filled with hydraulic fluid. The hydraulic fluid was then pressurized and a load was applied to the coating outward from the interface to cause the coating to fail. Eight measurements were taken for each coating and the average value was defined as the burst pressure. The burst pressure was taken as a measure of the mechanical strength of the coating for a particular coating thickness. The burst pressure can then be used to evaluate different coatings of essentially the same thickness. Burst pressure for the three coatings is 0.0044 inch (0.11 mm) thick.
5400psi (390Kg/ ^cm2 ), thickness 0.0083 inch (0.21)
10,300 psi (724 Kg/cm ² ) at a thickness of 0.0105 inch (0.27 mm) and 13,200 psi (928 Kg/cm ² ) at a thickness of 0.0105 inch (0.27 mm). By linear regression, the burst pressure for a 0.0067 inch (0.17 mm) thick coating is
Estimated to be 8300psi (580Kg/cm ² ).

In addition, the wear characteristics of the applied coating are
Determined using the standard dry sand/rubber wheel abrasion test described in ASTM Standard G65-80, Procedure A. In this test, the coated specimens were loaded by a lever arm against a rotating wheel having a chlorobutyl rubber rim around the wheel. An abrasive (ie, 50-70 mesh Ottawa silica sand) was introduced between the coating and the rubber wheel. The wheel was rotated in the direction of abrasive flow. The specimens were weighed before and after testing and their weight loss was recorded. Because the densities of different types of materials tested vary widely, it is common to convert weight loss to volume loss in order to assess the relative ranking of materials. Coated specimen tested (conventional W-Co-Cr-C coating)
Average capacity loss about ^1.7mm3 per 1000 revolutions
It was hot.

The hardness of the coating was also measured by standard methods. The average hardness was found to be 1100DPH ₃₀₀ .

EXAMPLE Test specimens of AISI 1018 steel were prepared in the same manner as described in Example 1, including one specimen for hydraulic testing. The surface of the specimen was then coated using a D-gun and a cast and crushed powder of the following composition: 14.1% by weight Co, 4.8% by weight Cr, 4.2% by weight C, balance W. The powder size was -325 mesh. In addition, acetylene was used as a fuel gas. The oxy-fuel gas ratio in the D-gun was 0.98. The feed rate was 100 grams/min.

Chemical analysis of the coating was performed using the same method as described in the example. Analysis showed the following composition: 16.5% by weight Co, 4.9% by weight Cr, 3.7% by weight C, balance W.

The same hydraulic test was used to determine the mechanical strength of the coating. The burst pressure for this particular coating is 0.0068 inch (0.17 mm) thick.
It was 27900psi (1960Kg/cm ² ).

In addition, a wear test was conducted using ASTM standard G65-80 and procedure A. The average volume loss for the coated specimens was 1.8 mm ³ per 1000 revolutions.

We also measure the hardness of the coating.
It turned out to be 1000DPH ₃₀₀ .

This example was made in accordance with the above co-pending application and shows a coating containing a high content of cobalt, i.e. 11.0-18.0% by weight, and having improved toughness and strength. The abrasion resistance of this particular coating is approximately equal to the prior art coating shown by Example 1.

EXAMPLE Test specimens of AISI 1018 steel, including one specimen for hydraulic testing, were prepared in the same manner as described in the example. The surface of the specimen was then coated using a D-gun and a cast and crushed powder of the following composition: 12.0% by weight Co, 2.1% by weight Cr, 4.9% by weight C, balance W. The powder size was -325 mesh. In addition, acetylene was used as a fuel gas. The oxy-fuel gas ratio in the D-gun was 0.98. The feed rate was 150 grams/min.

Chemical analysis of the coating was performed using the same method as described in the example. The analysis showed the following composition: 17.9% by weight Co, 2.8% by weight Cr, 4.1% by weight C, remaining W _0. The same hydraulic test was used to determine the mechanical strength of the coating. The burst pressure for this particular coating is 0.0067 inch (0.17 mm) thick.
It was 26500psi (1860Kg/cm ² ).

In addition, a wear test was conducted using ASTM standard G65-80 and procedure A. The average volume loss for the specimens was 3.6 mm ³ per 1000 revolutions.

We also measure the hardness of the coating.
It turned out to be 1000DPH ₃₀₀ .

This example also shows a coating made in accordance with co-pending application no. 1 that has high strength, but has lower abrasion resistance than the prior art for the example.

EXAMPLE Test specimens of AISI 1018 steel, including one specimen for hydraulic testing, were prepared in the same manner as described in the example. The surface of the specimen was then coated using a D-gun and a cast and crushed powder of the following composition: 9.6% by weight Co, 9.5% by weight Cr, 4.9% by weight C, balance W. The powder size was -325 mesh. In addition, acetylene was used as a fuel gas. The oxy-fuel gas ratio in the D-gun was 0.98. The feed rate was 150 grams/min.

Chemical analysis of the coating was performed using the same method as described in the example. Analysis showed the following composition: 6.9% by weight Co, 6.9% by weight Cr, 4.2% by weight C, balance W.

The same hydraulic test was used to determine the mechanical strength of the coating. The burst pressure for this particular coating is 0.0068 inch (0.17 mm) thick.
It was 13000psi (912Kg/cm ² ). This represents a 50% increase in strength compared to the coated specimens tested in the examples.

In addition, a wear test was conducted using ASTM standard G65-80 and procedure A. The average volume loss for the specimens was 1.0 mm ³ per 1000 revolutions.

We also measure the hardness of the coating.
It turned out to be 1209DPH ₃₀₀ .

This example describes a coating made in accordance with the present invention that has moderately high strength and excellent abrasion resistance. The coating has a fast deposition rate,
That is, even though the coating was applied at 150 g/min, no cracking or shattering occurred.

EXAMPLE Test specimens of AISI 1018 steel, including one specimen for hydraulic testing, were prepared in the same manner as described in the example. The specimen surface was then applied using a plasma spray torch and a conventional sintered powder of the following composition: 10% by weight Co, 4% by weight Cr, 5.2% by weight C,
Remaining W. The powder size was -325 mesh.

Chemical analysis of the coating was performed using the same method as described in the example. Analysis showed the following composition: 9.2% by weight Co, 3.5% by weight Cr, 5.0% by weight C, balance W.

The same hydraulic test was used to determine the mechanical strength of the coating. Burst pressure for this particular coating is 9600 psi at 0.0069 inch (0.18 mm) thick
(670Kg/cm ² ). In this coating, 8
Instead of one measurement, seven measurements were performed.

In addition, a wear test was conducted using ASTM standard G65-80 and procedure A. The average volume loss for the coated specimens was 9.3 mm ³ per 1000 revolutions. The abrasion resistance of this coating was poor even when compared to that of the conventional D-gun coating of the example. This should be expected with plasma spray coatings, which do not hold up as well as D-gun coatings.

We also measure the hardness of the coating.
It turned out to be 687DPH ₃₀₀ .

EXAMPLE Test specimens of AISI 1018 steel, including one specimen for hydraulic testing, were prepared in the same manner as described in the example. The specimen surface was then applied using a plasma spray torch and cast and crushed powder with the following composition: 9.6 wt.% Co, 9.5 wt.% Cr, 4.9 wt.
Weight %, remainder W. This was the same powder composition used in preparing the example coating. The powder size was also the same, ie -325 mesh.

Chemical analysis of the coating was performed using the same method as described in the example. Analysis showed the following composition: 8.7% Co, 8.1% Cr, 3.8% C, balance W.

The same hydraulic test was used to determine the mechanical strength of the coating. Burst pressure for this particular coating is 9300 psi at 0.0064 inch (0.16 mm) thick
(653Kg/cm ² ).

In addition, a wear test was conducted using ASTM standard G65-80 and procedure A. The average volume loss for the coated specimens was 6.7 mm ³ per 1000 revolutions.
The wear rate for this coating was approximately 1/3 lower than that for the plasma spray coating of the previous example using conventional sintered powder.

In addition, the hardness of the coated test piece was measured to be 775DPH _300.
It turns out that it is.

From the foregoing it can be seen that the present invention provides a novel W--Co--Cr--C coating system with improved strength and superior wear resistance.
The D-Gun coating of the present invention has a coating thickness of approximately 0.006 inches (0.15 cm) and a coating weight of approximately 13,000 lbs.
It can withstand hydraulic pressures in excess of in ² (914 kg/cm ² ) and exhibits a wear rate of only about 1.0 mm ³ per 1000 revolutions. Even the plasma coatings of the present invention have lower wear rates than prior art plasma coatings. Moreover, the coating can be applied with fast deposition rates and is free from cracking and spalling.

Although the powder and coating compositions are defined herein by certain ranges for each of the essential ingredients, it will be understood that various impurities may be present in small amounts. Iron, usually resulting from the grinding operation, is the major impurity in the coating and can be present in amounts up to about 1.5, and in some cases up to 2.0%, by weight of the composition.

Although the above examples only include D-gun and plasma spray coatings, other thermal spraying techniques such as "velocity" plasma, "supersonic" combustion spraying processes, or various other detonation devices may be used. It will be appreciated that coatings of the present invention can be manufactured.

Claims (1)

Claims: 1. essentially about 4.0 to about 10.5% by weight cobalt;
About 5.0 to about 11.5% chromium by weight and about 3.0 to about 5.0% carbon
% by weight and the balance tungsten. 2. essentially about 5.5 to about 7.5% by weight cobalt;
About 5.5 to about 7.5% chromium by weight and about 3.0 to about 5.0% carbon
% by weight and the balance tungsten. 3 Coating thickness approximately 0.0060 inch (0.15 mm)
The coating composition of claim 1 having sufficient mechanical strength to withstand hydraulic pressures in excess of about 13,000 pounds/in ² (910 Kg/cm ² ). 4. A coating composition according to claim 1 having a hardness value of more than 1000 DPH ₃₀₀ . 5 The support is steel, stainless steel, iron-based alloy, nickel, nickel-based alloy, cobalt, cobalt-based alloy, chromium, chromium-based alloy, titanium, titanium-based alloy, aluminum, aluminum-based alloy, copper 2. The coating composition according to claim 1, wherein the coating composition is a metal material selected from the group consisting of , a copper base alloy, a heat-resistant metal, and a heat-resistant metal base alloy. 6. The coating composition according to claim 1, wherein the support is a non-metallic material selected from the group consisting of carbon, graphite, and polymer. 7 Suspending the powder coating material in a high temperature, high velocity gaseous stream, heating it to a temperature at least close to the melting point of the powder material, and directing the gaseous stream towards the surface of the support to remove the powder coating material. in a method of coating a support in which the powder coating material is deposited on the support to form a coating consisting essentially of about 4.0 to about 10.5 weight percent cobalt and about 5.0 to about chromium. 11.5% by weight of a coating, about 3.0 to about 5.0% by weight of carbon, and the balance tungsten. 8 The powder coating material is characterized in that the coating deposited on the support comprises essentially about cobalt.
5.5 to about 7.5% by weight and about 5.5 to about 7.5% by weight of chromium
and about 3.0 to about 5.0 weight percent carbon, the balance tungsten. 9. The method of claim 7, wherein the powder coating material is suspended in a high temperature, high velocity gaseous stream produced by a detonation device. 10. Claims in which the powder coating material has a composition consisting essentially of about 8.0 to 11.0 weight percent cobalt, about 8.0 to about 11.0 weight percent chromium, about 4.0 to about 5.5 weight percent carbon, and the balance tungsten. The method described in Section 7. 11. The method of claim 7, wherein the powder coating material is suspended in a high temperature, high velocity gaseous stream produced by a plasma arc torch. 12. The method of claim 11, wherein the powder coating material has a composition that is substantially the same as the composition of the coating. 13 feeding a mixture of oxygen and fuel gas along with a powder coating material into the barrel of a detonation gun; igniting the mixture of oxygen and fuel gas to create a detonation wave along the barrel to bring the powder coating material to a high temperature; accelerating in a high velocity gaseous stream; directing the gaseous stream towards a surface of a support to deposit the powder coating material on the surface to form a coating; the coating deposited thereon consists essentially of about 4.0 to about 10.5 weight percent cobalt;
About 5.0 to about 11.5% chromium by weight and about 3.0 to about 5.0% carbon
% by weight and the remainder tungsten. 14 The powder coating material is characterized in that the coating deposited on the support comprises essentially about cobalt.
5.5 to about 7.5% by weight and about 5.5 to about 7.5% by weight of chromium
and about 3.0 to about 5.0 weight percent carbon, the balance tungsten. 15. The method of claim 13, wherein the ratio of oxygen to fuel gas in the mixture is approximately 1.0. 16. Claims wherein the powder coating material has a composition consisting essentially of about 8.0 to about 11.0 weight percent cobalt, about 8.0 to about 11.0 weight percent chromium, about 4.0 to about 5.5 weight percent carbon, and the balance tungsten. The method according to scope item 15. 17 Essentially about 8.0 to about 11.0% by weight cobalt
, about 8.0 to about 11.0% by weight of chromium, and about 4.0 to about carbon
A powder coating composition for applying a high-strength, abrasion- and corrosion-resistant coating to a substrate by a thermal spraying process comprising about 5.5% by weight and the balance tungsten. 18. A powder coating composition according to claim 17, comprising a cast and a crushed powder. 19 a support and a coating applied to the support by a thermal spraying process, the coating comprising essentially from about 4.0 to about 10.5% by weight cobalt;
A product consisting of about 5.0 to about 11.5 weight percent chromium, about 3.0 to 5.0 weight percent carbon, and the balance tungsten. 20 said coating is essentially about cobalt.
5.5 to about 7.5% by weight and about 5.5 to about 7.5% by weight of chromium
and about 3.0 to about 5.0 weight percent carbon, and the balance tungsten.