CH625561A5 - Object from a base metal with a refractory metal coating - Google Patents

Description

The invention relates to an object made of a base metal with a refractory metal coating and a method for producing the object.

The invention is based on the knowledge that any base made of a metal, a metal alloy or a metal-containing material can be provided with a coating of a refractory metal with a melting point of at least 1490 ° C. if such a base is brought together with an electrolyte which is at least partially between the refractory metal particles and the surface of the backing material. Accordingly, the object is characterized in that the base metal has a zone in the region of the surface thereof in which a refractory metal consisting of individual particles with a melting point of at least 1490 ° C. is adhesively deposited on the base metal, with a number of adjacent particles each in nests are joined together, which are at a distance from one another and form the overall coating.

Of the refractory or protective metals that can be used, the following metals in powder or single particle form and all alloys containing these metals should be mentioned: boron, chromium, cobalt, iridium, molybdenum, niobium, osmium, palladium, platinum, rhenium, rhodium , Ruthenium, tantalum, thorium, titanium, tungsten, io vanadium, yttrium, zircon.

The starting form of these metal particles can be idiomorphic, block-like, coaxial, spherical, acicular or dentritic. The size of these particles is preferably as small as possible and is usually between 0.01 (im and 15 approximately 1 mm. The base materials on which the refractory materials should be applied can be aluminum, iron, chromium, cobalt, nickel, copper , Magnesium, tin, titanium or an alloy of these metals, for example steel, cast iron, brass, bronze, 20 solder, etc. However, it can also be any other suitable base metal.

The refractory metal present in the form of individual particles is expediently applied in the region of the surface of the base material with the aid of a finely divided electrolyte 25 which is at least partially located between the refractory metal and the base material.

Of the electrolytes that have proven to be suitable, acids such as mineral acids, hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, perchloric acid, fluorosilicic acid, etc., and the acid anhydrides, such as arsenic trioxide and chromium trioxide, etc., and the organic acids , Tartaric acid, malonic acid or the like. Suitable basic electrolytes are alkali metal and alkaline earth metal hydroxides, such as sodium, potassium, lithium, calcium, magnesium hydroxide 35 etc. Also suitable as electrolytes are: alkali metal and alkaline earth metal salts of the abovementioned acids, such as the alkali metal halide salts, in particular the chlorides, Chlorates, fluorides, nitrates, sulfates, phosphates, carbonates etc., as well as metal salts, the metal used as part of the electrolyte being one of the metals mentioned above as refractory metal or as the base metal, and such a metal being any salts can form, for example sulfates, phosphates, nitrates, carbonates, chromates, molybdenates, tungstates etc.

45 Also suitable as electrolytes are other chemical compounds, such as ammonium thiocyanate, potassium thiocyanate, zinc sulfate, ammonium carbonate, ammonium sulfate, potassium sulfate, sodium sulfite, sodium carbonate, potassium cyanide, calcium nitrate, potassium chloride and calcium chloride.

The electrolyte can generally be any acid, base or salt. It must dissociate in the presence of moisture, i.e. he must be able to conduct electricity, and a sufficient level or percentage of ss dissociation is also required. More specifically, the electrolyte must have a sufficiently high equivalent conductance.

The conductance is the ratio between the equivalent conductance at a dilution of 1 g equivalent per 101 60 water and the equivalent conductance at an infinite dilution, the temperature being 25 ° C (see "The Physical Chemistry of Electrolytic Solutions", Harned and Owen , Rheinhold Publishing Corp., 1958). The electrolytes suitable according to the invention are those with conductivities between 65 and about 0.13 and 0.93 and preferably above 0.60.

Some acids, bases and salts and the corresponding approximate equivalent conductivities are given below which meet the requirements of the invention:

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Acids

Bases

Hydrochloric acid 0.90

Sodium hydroxide

0.88

nitric acid

0.92

Potassium hydroxide

0.93

sulfuric acid

0.60

Calcium hydroxide

0.80

Strontium hydroxide

0.86

Barium hydroxide

0.86

Salts

Super nitrate

0.86

sodium

0.61

Potassium chloride

0.86

Ammonium sulfate

0.59

Sodium chloride

0.82

Barium nitrate

0.57

Potassium bromide

0.92

Strontium nitrate

0.62

Sodium nitrate

0.82

Lead nitrate

0.54

Sodium acetate

0.79

Copper (II) acetate

0.33

Potassium chlorate

0.83

Zinc sulfate

0.38

Calcium chloride

0.75

Copper sulfate

0.38

The dissociation is a criterion for the selection of an electrolyte to carry out the proposed method. As the electrolyte dissociates, its ability to cause the desired reaction increases. One can assume that the more complete the ionization of an electrolyte, the more effectively it can be used in the proposed sense.

In order to introduce the refractory or protective material into the surface of the base metal or to apply it to the surface, no electrical current has to be applied, since the internally generated electrolytic currents are of a sufficient size on a microscopic scale. However, it was found that the process is influenced in a positive sense by the application of an electrical current.

When the refractory metal is applied to the base material, an electrochemical reaction takes place, the refractory metal, which is in the form of individual particles, interacting with the electrolytes and the base material. When using solid electrolytes, the exact total particle size of the electrolyte and the refractory metal is not important, since this size depends mainly on the dimensions of the usually harder refractory metal. The electrolyte particle size preferably ranges from 10-3 microns to about 1 mm, with the particles preferably being 10 to 100 times smaller than the associated refractory metal particle at the time of application to the base metal.

To initiate the reaction in which part of the base metal is exchanged for the refractory metal, the refractory metal is partially ionized, whereby the exchange reaction with the base metal is started. The ion concentration should be between 1 and 60,000 mg, preferably between 1,000 and 15,000 mg of the refractory metal ion per liter of the solution.

The refractory metal ion, after having undergone an exchange reaction with the base metal, forms a point at which the particle is deposited from the refractory metal, the reactions taking place only on a microscopic scale. In order to generate refractory metal ions in a sufficient amount and to initiate the desired reactions, the refractory metal must at least partially have a nascent fresh surface. The required concentration of refractory metal ions in the presence of electrolytes and the moisture present is generated on these fresh surfaces for reasons that have not yet been fully clarified. Although all refractory metals are insoluble in the existing moisture in the conventional sense of the word, sufficient ion concentrations are nevertheless formed from the nascent surfaces of the refractory particles in the presence of electrolytes and sufficient moisture. The required nascent surface can easily be generated mechanically, for example by rubbing, grinding, mixing by abrasion or by a chemical action of the electrolyte or another reactive material.

The extent of the mechanical or chemical effect for producing the nascent surface is not decisive, since each mixing produces a certain nascent surface. The refractory metal ions are formed in a period of about 1 minute to 30 days, preferably in 1 to 20 hours, the time depending on the moisture, temperature and solubility of the refractory metal and is therefore not critical. It is only essential that the required concentration of the refractory metal ions is present and that a certain nascent surface is created, the refractory metal present in the form of individual particles being deposited in the area of the surface of the base metal.

To create the intimate relationship between the electrolyte and the refractory metal in the form of individual particles and to bring the electrolyte between the surface of the base metal and the refractory metal and to cause a larger nascent surface to form on the particles of refractory metal, different methods are possible. If the refractory metal is a dry powder under ambient conditions and the electrolyte is in dry granular form, then an intimate mixture can be made by thoroughly mixing the two powders. The amount of the refractory metal can be between 99 and 50 and preferably between 96 and 66% by weight of the dry mixture of refractory metal and electrolyte. Accordingly, the electrolyte can be 1 to 50, and preferably 4 to 34% by weight of the dry mixture of refractory metal and electrolyte.

To increase the electrochemical effect, an element or a compound can be introduced which serves as a means for preventing electrochemical polarization. The addition of the refractory metal in the form of individual particles and the electrolyte in an amount of 1 to 10 wt .-%, based on the total mixture of refractory metal and electrolyte. Examples of such depolarizing compounds or elements are MnO 2, platinum metal powder, CuO, HgO, ionizable iron or tin salts such as the halides, sulfates, nitrates etc., and activated carbon.

The thickness of the electrolyte coating on the refractory particle should be continuous and uniform. It can vary from molecular films up to 25 micrometers or above up to 1 mm. Preferably a larger part of the refractory metal surface should be coated, however a smaller part of only about 10% is acceptable.

Mixing or trituration to produce one or both of the nascent surfaces on the refractory metal particle and coating the refractory particle with an electrolyte powder can be advantageously accomplished when both the electrolyte and refractory metal powders are substantially dry by only have little or no moisture. Mixing usually takes about 30 minutes to 30 days. Sufficient moisture is essential to generate the refractory metal ions, otherwise no ions will form.

Regardless of whether the refractory metal and / or the electrolyte are dry under ambient conditions, there should be water in the mixture of refractory metal and electrolyte

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in an amount of about 0.5 to 60% by weight, based on the total mixture, before the base metal is treated with the mixture. The amount of moisture should preferably be 1 to 40% by weight.

It is also appropriate to form an intimate moist mixture of the electrolyte and the refractory metal in the form of a paste, slurry or solution in a liquid medium such as water.

A sufficient amount of water in the mixture may be present when the electrolyte exhibits an electrical resistance less than about 106 ohm-cm. If the electrolyte is liquid, the addition of a liquid medium may be unnecessary, but is preferable, especially in the case of strong mineral acids.

The presence of some water in the mixture of refractory metal and electrolyte is important in order to generate the ion concentration of the protective metal and in view of the fact that the reactivity of the electrolyte is likely to cause an ion exchange with the base metal.

This simple mixing step or the combined mixing and aging step, if carried out over a period of 10 minutes to 30 days, can replace the time required for the generation of the nascent surfaces and the concentration of refractory metal ions, although if the Concentration of the refractory metal ions is not sufficient, remixing and / or further aging may be required for a period between 1 and 30 days. The actual concentration of the refractory metal ions is the test for the need to adhere to another mixing or aging period.

The intimately mixed powders, pastes, liquids, etc. of the electrolyte with the refractory metal can then be applied by spraying, dipping, brushing, tumbling, spraying, or by any other method of distribution or stratification using the mixture of refractory metal and electrolyte to form a thin coating be applied to the base material.

The mixture of the refractory metal with nascent surfaces and the electrolyte with the required moisture content and the necessary concentration of refractory metal ions is processed in a special ball mill with the parts to be treated, which ball mill works without balls. In this way a. there is sufficient coating of both the refractory metal and the electrolyte and thus carry out the next step, namely the deposition of the refractory metal. In the case of the wet mix, the electrolyte is between the surface of the backing metal and the refractory metal and acts in exactly the same way as in the case where the particles of the refractory metal have been coated with the electrolyte.

The base metal can be replaced by the refractory material at ambient temperature or at any suitable temperature, since the temperature is not critical with regard to the mode of operation and the feasibility of the invention. It has the effect of increasing the reaction rate as the temperature rises. It has been found that at ambient temperature, a time of about 1 to 168 hours, preferably 6 to 72 hours, is sufficient to impregnate the base material with the refractory material or to replace the base material with the refractory metal. Even longer times are not disadvantageous and do not affect the process. Shorter times may be appropriate if there is an adequate response. The temperature range can be between 0 and 200 ° C, preferably between 10 and 100 ° C

and in particular between 15 and 40 ° C. The lower limit of the temperature is not critical. It can also be lower than 0 ° C, but this entails a longer reaction time.

The areal density of the mixture of electrolyte and refractory metal as a protective material which can be applied to the base metal can vary from about 0.5 refractory particles of the protective coating / mm 2 to a completely uniform coating of the mixture on the surface of the base metal, which is approximately 106 particles / mm2 corresponds to a particle size of 1.0 micrometer. For complete coverage with particles from 1 to 5 microns in size, a concentration of these particles of approximately 4X104 to 106 particles / mm 2 is achieved. In the case of particles of approximately -325 mesh (nominal maximum diameter 44 microns), which include commercially available metal powder in combination with an electrolyte, the concentration of particles to be deposited on the backing metal can be from approximately 10 to 104 particles / mm2 fluctuate. The amount and size of the refractory metal particles applied determines the proximity of the particles and the size of the individual particles, which are then actually applied to the base.

The attached drawing shows schematically the various possible structures, on the base metal 10 and in the area of the surface 12 delimited by the planes A-A.

The properties of the individual particles 14 made of refractory metal, which are deposited in the surface areas of the base material, depend to a certain extent on the implementation of the invention. For example, refractory metal particles in the surface area of the base can have essentially the same shape and the same or somewhat smaller size than the powdery particles of refractory metal which were used as the starting material for carrying out the method. This characteristic was confirmed by microscopic examination of both the refractory metal powder and the single particle material used to carry out the process and the deposited refractory metal particles in the processed metal base.

A large number of such embedded particles have dimensions of no more than 2 micrometers. All of the refractory metal particles introduced in this way have been found to be between 0.01 and 100 micrometers in size.

Furthermore, a certain amount of refractory metal particles 14 can be deposited in the area of the surface 12 of the base metal 10, which have both larger and smaller dimensions than the nominal average particle size of the refractory metal powder of the individual particle material that was used to carry out the method. For example, if the initial shapes of the refractory metal particles used to carry out the process are idiomorphic or block-like and have an average dimension of 1 micrometer, the deposited, refractory metal particles can have such properties and, in addition, both the shape of large spherical particles with a diameter of up to 10 microns as well as small abutting particles with an average dimension of less than 0.2 microns. The deposited refractory metal particles 10 can take such additional forms, but it has been found that these particles are from 0.01 microns to 100 microns in size, with a plurality of the refractory particles having dimensions less than about 2 microns.

The places where the individual refractory metal parts5

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Chen are preferably located at the grain interfaces, the pores or depressions with a microscopic nature, in the portion near the surface of the base metal and / or within any irregularities in the area of the surface of the base metal, which have been generated by previous physical or chemical effects can be, for example, in recesses 16, which have been created by machining, etc. The distribution of refractory metal particles on essentially planar microscopic single-phase surfaces of the base metal is obviously spatially arbitrary. Similarly, it can be assumed that the appearance of microelectrolysis occurs essentially in an arbitrary spatial manner on such planar parts of the base metal, forming the initially discontinuous pattern of the individual refractory metal particles deposited.

Nests 18 are then formed from these refractory metal particles and are randomly distributed on the essentially planar surfaces 20 of the base metal. These particle nests are arranged at a distance from one another and are preferably formed in the region of the surface of the base metal in the event of irregularities, such as depressions 16, which go back to processing.

The proposed process reactions can be developed further, for example, by increasing the treatment time or by increasing the treatment temperature or the like. It is thereby achieved that the nests 18 formed irregularly from individual particles 14 adjoin adjacent nests, as a result of which microscopic (small-scale) zones 22 are formed from deposited refractory metal in the zone near the surface of the base metal. Such microscopic zones made of deposited refractory metal extend continuously and cover the base metal within the zones. These microscopic zones 22 made of refractory metal are irregularly arranged at a distance from one another and are preferably formed on irregularities, for example on recesses 16 or the like due to processing, in the zone near the surface of the base metal.

Since the diversity of the reacting surfaces is increased by increasing the surface density of the individual particles on the substrate, the mutual binding capacity of the refractory metal becomes clearer. Both preferred and irregularly arranged microscopic zones 22 of refractory metal extend to other adjacent microscopic zones of refractory metal, such as at location 24, with macroscopic zones 26 of deposited refractory metal in the zone near the surface of the base metal be formed. Such macroscopic zones 16 made of deposited, refractory metal appear to the unarmed eye continuously, since the base metal is covered within such zones. These macroscopic zones of deposited, refractory metal are arranged at a distance from one another and are obviously arranged irregularly in the zone in the region of the surface of the base material.

Subsequently, the entire base metal 10 is coated with the refractory metal and shielded from it with continuous lateral growth of the refractory metal, as shown at 28. Furthermore, the refractory metal is removed perpendicular to the surface of the backing by thickening the refractory metal layer at location 30. In this way, an adherent and continuous layer 32 of refractory metal is produced which is bonded to the base metal 10 and forms an integral part of the same.

Such a distribution and subsequent connection of the separated individual refractory metal particles in the manner described above results in a deposition pattern which is different from any other metal deposition process, in particular electrochemical processes. If, for example, a metal sheet made of river steel is treated according to the invention, the unarmed eye sees a continuous coating which can withstand a bend of 140 ° by a radius of 3 mm (3 / s inch).

without there being any visible cracks or tears. This coating, although appearing continuous, has a discontinuous structure.

The treatment of a tool steel base by the method according to the invention requires the application of individual refractory metal particles in the form of arbitrarily arranged particle nests. These particle nests arise in the zone in the area of the surface of the base metal, preferably on the essentially planar metal matrix, which is exposed between the carbide particles of this steel. Treatment of SAE 1018 steel using the proposed method gives a similar but more complex pattern of deposition of refractory metal particles in the area of the backing. In this case, the refractory metal particles are deposited individually in the form of irregularly arranged particle nests on the essentially planar ferrite micro-component of the base and additionally preferably distributed on the intermediate car-bid-ferrite part of the pearlite micro-component of the base metal. In the case of both types of steel, the continuous metal phase is the preferred location for the deposition of refractory metal particles. In both cases, irregularly spaced nests of individual particles are observed, which are deposited on essentially planar sections of the continuous metal matrix phase of the support.

The build-up thickness of the deposited particles, which form an adhesive coating, can vary according to the time, the temperature and the ion concentrations. Current applied during a certain period of time during which the electrolyte or refractory metal is in contact with the base material can also affect the coating properties. A thickness that begins with molecular films, which can be selectively continuous or discontinuous, and is up to 0.5 mm, can be deposited in the region of the surface of the base material. It should also be pointed out that the refractory metal which is applied to the base metal replaces part of the same, so that no change in the dimension of the base metal can be determined by conventional measurement methods. A dimensional change can only be perceived in the most advanced state of deposition.

According to a particular embodiment, microscopic amounts of at least one corrosion product 24 can be present in the zone in the area of the surface of the base metal. These corrosion products are the solid chemical compounds that are substantially insoluble in the electrolyte, which are formed as a result of any corrosion reaction in which the parent metal is chemically attacked by the electrolyte. Most of these compounds consist of cations from the base metal and anions from the electrolyte. The corrosion products can occur as base metal hydroxide, chlorides, nitrates, sulfates, cyanates, acetates, carbonates or the like; it can also be more complex base metal compounds, such as oxyhydrates, oxychlorides, thiocyanates or the like.

If there are corrosion products, they tend to nucleate and grow in zone 12 in the s

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Areas of the surface of the base 10 as well as at the locations that are accessible to the electrolyte, in particular at locations where the refractory metal is not in direct physical contact with the base. The essentially lateral growth of the corrosion products tends to the effect that the refractory material deposited in the form of particles 14, nests 18, microscopic zones 22 and macroscopic zones 26 is surrounded by the corrosion products (see reference number 36) is embedded (see reference number 38), is partially embedded (see reference number 39) or is enclosed by it (see reference number 40). Since these corrosion products adhere to the base metal, it is believed that they require the refractory metal particles to adhere more firmly to the base, especially if the refractory metal particles are surrounded or enveloped.

The composite coating structure formed in this way consists of refractory metal particles that are adhesively bonded to the underlay metal, refractory metal particles that are surrounded or enclosed by the corrosion product or that adhere even more firmly to the substrate due to corrosion products, and additionally some refractory metal particle material that is completely enveloped by the corrosion product is. Such a composite structure increases the likelihood that certain refractory metal particles, in particular those which are completely encased by the corrosion product, are mechanically embedded in the base metal, welded into the base metal by friction, in the region of the surface zone, as a natural result of forces which are generated when the coated part is put into operation. In this sense, the composite coating or composite coating acts as a reservoir, which ensures a continuous supply of refractory metal individual material that adheres in the zone near the surface of the underlying metal. In some cases, the corrosion product itself acts as a lubricant to reduce friction and / or wear either by its own properties or as a porous reservoir for conventional lubricants such as oils, greases, graphite, molybdenum disulfide or the like.

The preferred final stage of the proposed treatment of base metals consists of a quick wash with hot water and subsequent quick air drying. This measure ends the microelectrolytic effect, with virtually all ionized products and salts being removed from the vicinity of the base metal substrate. The run-off washing liquid, usually water, contains valuable, non-deposited, refractory metal particles, the recovery and use of which is expedient. Up to 99% of the total weight of the refractory metal particles can be recovered by standard measures, for example by clarifying, sedimentation, centrifuging or the like of the washing water running off, but not all refractory metal particles can be recovered in this way.

There are specific combinations of refractory metals and electrolytes that unfortunately combine with each other after the washing cycle. This bonding is undesirable because the product so formed cannot be used for recycling purposes and cannot be easily converted back into particles. In such cases, mineral acid treatment of the wash water is expedient, the concentration of the acid in the wash water being kept between 1 and 10% by volume, based on the total amount, in order to avoid the binding or cementing process.

For example, it has been found that in the case of a treatment mixture of tungsten metal powder as the refractory metal and calcium chloride as the electrolyte, the cementation can be avoided by adding hydrochloric acid in an amount of approximately 5% by volume based on the total wash water running off, followed by the Wash and clarify or centrifuge the drain again to recover the tungsten powder that was not consumed in the treatment reaction. The concentration of hydrochloric acid to reach a corresponding wash water concentration is not critical.

The following examples are intended to explain the invention further:

example 1

Tungsten powder in pure form is used to apply tungsten metal as an abrasion-resistant, refractory material in the zone in the area of the surface of textile machine outrigger rings made of steel with a high carbon content, but there are no special requirements for the purity. This powder has a size of 1-325 mesh (particles that pass through a sieve with a mesh size of 0.045 mm). This shows that the tungsten metal particles have a maximum dimension of 45 micrometers, with many of the particles being significantly smaller than this size, down to approximately 1 micrometer maximum dimension. This dry tungsten powder is mixed with dry anhydrous calcium chloride powder with a commercially available particle size in a ratio of 1 part by weight CaCk to 10 parts by weight tungsten powder. These two powders are then mixed or ground together in a shaker ball mill for a period of approximately 24 hours, using porcelain balls in a 6 to 12 mm size porcelain jar. The use of a mortar and pestle during the same period is also satisfactory. During this joint grinding, it is believed that nascent surfaces are formed on the refractory tungsten particles. The particle size of the CaCk is reduced, the CaCk being applied or smeared onto the surfaces of the tungsten metal powder particles.

The jointly ground mixture of dry powders is then left in contact with moist air with a relative humidity of 60% for about 20 hours. Due to the hygroscopic nature of the CaCk, water is taken up by this mixture in an amount which corresponds to approximately 10 to 20% of the total weight of the moistened mixture. At this point, the majority of the CaCk has dissociated into ions, while a small amount of the tungsten metal powder has also gone into solution in ionic form, producing an equivalent concentration of approximately 3000 to 10,000 mg of the refractory metal ions per liter of the liquid phase of the mixture is. The moistened and aged mixture is then applied as a slurry to the excavation rings in such a way

that the rings are tumbled together with the mixture. The parts are previously cleaned in a CCk bath to remove grease, oil, or other foreign matter to expose the zone near the surface of the steel backing material of the rings for exposure to the mixture of electrolyte and refractory metal and to allow contact. During a period of 24 hours at room temperature, the refractory metal powder particles as well as the refractory metal ions, which act together with the electrolyte and the steel backing, produce a deposit of metallic tungsten particles in the zone near the surface of the steel backing of the rings. The final stage of processing the steel haul rings described above is a quick wash with

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hot (80 to 100 ° C) water and then quick drying in the air. The microelectrolytic effect is ended. In addition, ionized products and salts are removed from the vicinity of the steel substrate.

The product obtained is a steel part, in the zone of which tungsten metal is deposited in the vicinity of its surface in the form of randomly arranged nests of individual particles. This spatially discontinuous deposition of tungsten particles is interspersed with a solid corrosion product, which is believed to be essentially hydrated ferric oxides, deposited as a contiguous mass in the zone near the surface of the steel base are and adhere to it. This corrosion product surrounds, encases and partially overlaps the deposited tungsten particles, forming an adherent composite corrosion product layer on the steel backing.

The coated steel surfaces reveal themselves to the unarmed eye as uniformly coated and darkened, showing a macroscopic green color and preferably absorbing visible electromagnetic radiation in a wavelength range between 580 and 610 nanometers compared to an uncoated base. Such a quality of treated surfaces results in both increased absorption and increased emission of electromagnetic radiation, the latter being of particular importance with regard to the dissipation of radiant heat.

Example 2

In order to apply tungsten as an abrasion-resistant refractory metal to the surfaces of heat-treated bevel gears made of low-alloy steel, the wetted and aged mixture of tungsten and CaCh is produced exactly as in Example 1. This mixture is then applied in the form of a slurry by brushing onto the abrasion surfaces of the bevel gears in such a way that a surface density of approximately 103 refractory metal particles per mm 2 of the surface of the cleaned steel bevel gears is set. Within 24 hours at room temperature, the refractory metal ions work together with the electrolyte and the low alloy steel backing material to create a coating of metallic tungsten particles in the zone near the surface of the steel bevel gears. The wheels are then washed and dried as in Example 1.

Laboratory sliding abrasion tests on similarly treated low-carbon steel plates (type SAE 1018) show that at a load of 0.5 kg and a speed of 120 cm / sec. the treated material is approximately 250 times more resistant to abrasion than a similar untreated sample as measured by weight loss. The treated material used to perform these 1 hour accelerated abrasion tests has the same macroscopic appearance as the treated low alloy steel bevel gears described above.

Example 3

Tungsten powder with a size of -325 mesh (particles that pass through a sieve with a mesh size of 0.045 mm) is used to apply tungsten as an abrasion-resistant, refractory material to the surfaces of parts. The dry tungsten powder is mixed with dry anhydrous CaCk with a commercially available particle size. The powders are mixed as in Example 1 and ground together.

The co-ground mixture of the dry powders is then sprayed onto cleaned abrasion surfaces in such a way that a surface density of approximately 3 X103 refractory metal particles per mm 2 of the surfaces is set. Such abrasion surfaces are then exposed to air at 40 ° C with a relative humidity of 40 to 50% for a period of 20 hours. Within this 20 hour period, the refractory metal powder particles and the refractory metal ions act together with the electrolyte and the abrasion surfaces to produce a deposit of metallic tungsten particles in the zone near the surface of these abrasion parts.

Example 4

In order to apply tungsten as an abrasion-resistant refractory metal to the surfaces of parts, a wetted and aged mixture of tungsten and calcium chloride is produced exactly as in example 1. A relatively large amount of this mixture is then placed in a stainless steel vessel, which acts as a positive pole of an electrolytic cell. In this case, the wetted mixture serves as the "electrolyte" of the electrolytic cell. Taking into account the specified polarities, a DC voltage of approximately 1 volt is applied across the cell (stainless steel - "electrolyte" - substrate to be coated). In this way, the electric current is allowed to flow for a period of about 6 hours, after which it is found that the substrate has taken on the typical blue tone that also occurs in the case of the surfaces produced in accordance with Examples 1 and 3, in which case no power has been applied. In this case the application of the current results in an acceleration of the deposition of the discrete particles.

Example 5

Variously designed and shaped loop thread guides and needles made of hardened carbon steel as well as some loop thread guides and needles made of chrome steel and tufting knives made of a tungsten steel are exposed to the action of a mixture of 1.5 ccm hydrochloric acid and 20 g powdered tungsten (-325 mesh) Pass the sieve through with a mesh size of 0.045 mm]). The hydrochloric acid forms the electrolyte and is mixed in an amount of 1 part of the acid with 5 parts of water. The mixture of hydrochloric acid and tungsten is ground into a uniform mixture over a period of 24 hours before contacting the parts to be treated. After trituration, the mixture is in the form of a wet powder. The moisture content is adjusted to 9% by weight, based on the total mixture. After a 24 hour aging period, the tungsten ion concentration should be at least 5000 mg per liter of the solution. The desired product is then applied in an amount of 200 parts per mm2 evenly at 25 ° C to the surfaces of the loop thread guides, the tuft knives and the needles. These items are left in open troughs for a period of 12 hours. At the end of this period, all the pieces will look slightly darker. After the end of the reaction period, the pieces have surfaces with an abrasion resistance that lasts longer than that of untreated pieces.

The definitions of three terms used according to the invention are given below. Terms that are not defined are to be understood in their usual meaning:

Deposition involves the chemical, mechanical, or physical connection of one material to another and

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relates in particular to covering, binding, adhering and embedding.

Refractory metal ion concentration: This is the concentration of refractory metal ions in an aqueous solution on a weight basis, assuming that the metal itself is ionized in a monovalent or polyvalent state. This simple concept of ionization cannot reflect the actual case. For example, tungsten can occur in solution as tungsten, tungsten being intimately initiated with oxygen.

Zone in the area of the surface: The base metal and its immediate surroundings are considered to be the system in question. In parallel to the actual boundary between the parent metal and the environment, assume two surfaces, one on either side of the actual boundary that is far enough from that boundary so that all irregularities and inhomogeneities in the surface of the parent metal completely fall between them. The volume enclosed by these two surfaces is the "zone in the surface area" of the base metal. This definition corresponds to that of J. Willard Gibbs (cf. C. E. Reid “Principles of Chemical Thermodynamics”, Reinhold Publishing Company, New York, 1960). As for the structural details, the zone in the area of the surface depends on the measures used to produce the surface, but in general all such surfaces have characteristic openings, cracks or pores with an irregular size or shape as follows to: see broad or lateral dimensions between 0.02 microns and 1 mm and depth of about 0.02 microns to 200 microns, irregularly distributed over the surface of the object to be treated. Substantially planar surfaces of the base material remain between these openings. The openings may have an undercut and thus an overhanging portion of the surface that extends into the openings of the base material. In the present case, all such geometric structural details are defined as falling into the zone near the surface.

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1 sheet of drawings

Claims (30)

625 561 PATENT CLAIMS 1. Object made of a metal-containing base material with a heat-resistant metal coating, characterized in that the base material has a zone in the region of the surface thereof in which a heat-resistant metal consisting of individual particles with a melting point of at least 1490 ° C. is adhered to the base material, a number of adjacent particles are put together in nests, which form a multiplicity of macroscopic metal zones and overall the coating. 2. Object according to claim 1, characterized in that the heat-resistant metal consists of idiomorphic and equi-axial particles or only of idiomorphic or needle-shaped particles, the majority of the idiomorphic particles being less than 2 micrometers and the equiaxial particles being less than 10 micrometers. 3. Object according to claim 1, characterized in that the same in the region of the surface of the base material (10) has a zone formed by a solid corrosion product of the same, adhering to the base metal, which corrosion product at least partially surrounds other heat-resistant particles at locations where these others Particles do not adhere to the backing metal, so that these particles form an additional, abrasion-resistant coating. 4. Object according to claims 1 to 3, characterized in that the adjacent nests (18) form the same microscopic, refractory metal regions, at least some regions being at a distance from one another. 5. Article according to claims 1 to 4, characterized in that the same has a solid corrosion product (24) of the base metal in a zone (12) in the region of the surface, which adheres to the base metal in places that are not by microscopic sections or by refractories Particles are occupied, the corrosion product (24) at least partially surrounding the microscopic sections and holding other refractory particles (14) that are not firmly attached to the base metal (10), whereby a further abrasion-resistant coating is formed. 6. Article according to claims 1 to 5, characterized in that a plurality of the nests (18) with the formation of microscopic, refractory metal sections (30) adjoining each other and a plurality of such microscopic areas with formation of macroscopic locations (26) from the refractory metal adjoin each other on the base metal. 7. Object according to claims 1-6, characterized in that the zone (12) in the areas of the surface of the base metal (10) has irregularities, openings, cracks or pores with an irregular size or shape, a plurality of the nests (18) with formation of microscopic, refractory metal sections adjoining one another and a large number of these microscopic sections are located in the region of the surface with the irregularities, so that a partial coating through the microscopic points is present in the zone in the region of the surface. 8. Article according to claims 1-7, characterized in that the same has adjacent, macroscopic locations (26) which form a macroscopically continuous coating of the refractory metal on the base metal. 9. Object according to claims 1-8, characterized in that the same visible and infrared electromagnetic radiation absorbs more than the non-coated base metal in a technically pure state. 10. The article of claims 1-9, characterized in that it has a macroscopically gray color and absorbs visible electromagnetic radiation in a wavelength range between 580 and 610 nanometers more than an uncoated base material. 11. Object according to claims 1-9, characterized in that the metal for the base material is selected from aluminum, chromium, cobalt, copper, iron, magnesium, nickel, tin, titanium and alloys thereof such as steels, cast iron, brass, bronzes and solder is. 12. Article according to claims 1-11, characterized in that the refractory metal made of boron, chromium, cobalt, iridium, moldydane, niobium, osmium, palladium, platinum, rhenium, rhodium, ruthenium, tantalum, thorium, titanium, tungsten, vanadium , Yttrium, zirconium or alloys thereof is selected. 13. Article according to claims 1-12, characterized in that the same adhesive means for attaching individual particles of the refractory material to the base, which means are selected from groups that hydroxides, chlorides, nitrates, sulfates, cyanates, carbonates, acetates, Oxyhydrates, oxychlorides and thiocyanates of the base metal include. 14. Article according to claims 1-13, characterized in that these agents have further refractory metal particles that are not in contact with the metal base, the further refractory metal particles giving the base metal improved abrasion properties. 15. A method for producing an article according to claim 1 by applying a refractory metal to a base metal to increase the wear resistance, characterized by the following steps: Use of an electrolyte material which is capable of dissociating in ions and has a conductance between 0.13 and 0.93, calculated using a 0.1 normal solution, Use of a refractory metal present in individual particles with a melting point of at least 1490 ° C. which is to be deposited in the area of the surface of the base material, - Mixing 99 to 50 wt .-% of the refractory metal with 1-50 wt .-% of the electrolyte for a period of time sufficient to form nascent surfaces on each of the refractory metal particles to be deposited, which metal particles are at least partially surrounded by electrolytes , Maintaining a moisture content in the mixture sufficient to maintain an electrolyte resistivity of less than 10 6 ohms and to produce a concentration of 1-60,000 mg per liter of mixture of refractory metal ions, Contact and partially cover the surface of the base material with the refractory material in particle form and with this electrolyte mixture, - Implementation of the mixture with the base material at temperatures between 0 and 200 ° C and - depositing the refractory metal within the surface zone of the base material in the form of individual particles in order to obtain a protective surface for the base material. 16. The method according to claim 15, characterized in that the refractory metal is deposited in the form of individual particles. 17. The method according to claim 15, characterized in that the reaction is carried out at a temperature between 15 and 40 ° C. 18. The method according to claim 15, characterized in that in the zone in the region of the surface of the base metal, the refractory metal is deposited in a thickness of up to 0.5 mm. 19. The method according to claim 15, characterized in that an electrolyte with a degree of dissociation of 0.60 to 0.93 is used. 20. The method according to claim 15, characterized in 2nd s 10th 15 20th 25th 30th 35 40 45 50 55 60 65 3rd 625 561 that the electrolyte used consists of a mineral acid, an organic acid, a base, a salt of such an acid or base or an acid anhydride. 21. The method according to claim 15, characterized in that the refractory metal used is made of boron, chromium, Cobalt, iridium, molybdenum, niobium, osmium, palladium, platinum, rhenium, rhodium, ruthenium, tantalum, thorium, titanium, tungsten, vanadium, yttrium, zirconium or alloys thereof. 22. The method according to claim 15, characterized in that the refractory metal used has a particle size of 0.01 mm to about 1.0 mm. 23. The method according to claim 15, characterized in that the base metal used consists of aluminum, iron, chromium, cobalt, copper, nickel, magnesium, tin, titanium or an alloy such as steel, cast iron, brass, bronze or solder. 24. The method according to claim 15, characterized in that to produce the nascent surfaces, the mixing of refractory metal and electrolyte takes place over a period of approximately 30 minutes to 30 days. 25. The method according to claim 15, characterized in that to form the said concentration of the refractory metal ions, the refractory metal particles with nascent surfaces with the electrolyte and the specified moisture concentration during a period of Kept in contact for 10 minutes to 60 days. 26. The method according to claims 15 and 25, characterized in that a reaction time between 1 and 168 hours is observed. 27. The method according to claims 15 and 25, characterized in that a humidity of 0.5 to 60% is maintained. 28. The method according to claim 15, characterized in that an additive in the amount of 1-10 percent by weight of a material of the mixture is added as a means for preventing electrochemical polarization. 29. The method according to claims 15 and 25, characterized in that Mn02, CuO, HgO, platinum metal powder, ionizable iron and tin halides, sulfates, nitrates or activated carbon is added to prevent electrochemical polarization. 30. The method according to claim 15, characterized in that the product is washed with water and the refractory metal-containing outlet is treated with a mineral acid solution, in an amount which is 1-10 percent by volume of the mineral acid.