DE1185034B - Metal powder mixture containing metal carbide for the production of coatings on metal bodies by spray welding - Google Patents

Description

Metal powder mixture containing metal carbide for the production of Coatings on metal bodies by spray welding It is known to use metal coatings to be applied to metallic surfaces by spray welding. To this To do this, the desired metal or metal alloy is first sprayed on and then welds the sprayed-on compound to the metallic substrate. This combination of metal spraying and subsequent welding has resulted result in the term »spray welding«, which is commonly used for this type of work.

The metal is sprayed on in the first step after the metal spraying processes known in the art. One guides the one to be sprayed Mass to a heating zone, where it is melted or softened by heat, whereupon they are finely divided in a molten or thermo-plastic state sprayed on the substrate to be coated. You can see the spray weld mass of the Feed in the heating zone as a powder or in some cases also in the form of a wire, which was made from a powder held together by plastic masses. In this case, however, the plastic masses used for this purpose must also be included the heat developed in the heating zone, leaving behind the metal particles.

The subsequent melting together of the sprayed-on metal layer can be in appropriate ovens or with the help of a directly on the coated Carry out surface-facing welding torch.

So far, only a limited one has been used for the spray welding process Number of metal alloys commonly referred to as "spray-weld alloys" are found to be useful, namely those whose components have a flux effect and which are therefore referred to as "self-fluxing alloys".

These are uniform alloys, which as such already had "self-flowing" or "flowing" properties. They are composed differently than those alloys which a flux separated during the heating process must be added or in which such a flux z. B. in the form of a core or a rod is separate from the actual alloy.

The flow properties are achieved in the metal heating process the following effects: 1. reduction or dissolution of metal oxides, 2. washing away or coagulation of metal oxides, 3. Reduction of the surface tension of the metals and thereby an increase in their wettability, 4. delay or prevention an oxidation. The self-fluxing alloys bring the flow properties their flow components both during the injection process as well as during the following The welding process. The effect of the flow components extends during of the spraying process mainly depends on the oxide content of the sprayed coatings greatly reduce. This is a necessary requirement because of the larger amounts of oxide adversely affect the subsequent welding process in the sprayed coatings.

So far it has not been possible to use carbide-containing coatings Spray welding process in an impeccable manner and economically usable extent to apply to metallic substrates. One of the fundamental ones that occur here The difficulty lies in the fact that most carbides get through the flame spray equipment Do not allow the heat generated to soften enough to adhere and layers form. When using very fine powders with particle sizes below 44 microns excessive oxidation occurs in the flame. In addition, very diffused fine particles too largely in the auxiliary metal mass, which the metallic binding or carrier mass for the carbide particles, and lose their favorable physical properties.

It has hitherto been common practice to use welded-on coatings made of carbide-containing Applying substances by using welding wires in the usual way and doing so electrical devices or the flame to achieve the required welding temperatures used. In these processes, the carbide particles are sometimes fed separately into Form of powder or grains from a special filling container too. One also has the carbide particles by casting in an auxiliary metal forming the welding rod brought in. The welding rod can be produced in another way by first the auxiliary metal is formed into a tube into which a core made of carbide particles is formed brings in.

Whenever carbide-containing coatings by welding in an auxiliary metal are produced, there always occurs an undesirable deterioration of the carbide particles one, since these diffuse into the auxiliary metal and here at least partially to be resolved. Also in these processes, the carbide particles are oxidized damaged, except when complete shielding by inert gases is ensured is. In addition, no uniform distribution can be found in the weld application of carbide particles within the auxiliary metal. Hence lie in individual Areas of the pavement contain carbide particles in higher concentrations than in others. The former areas tend to be overly brittle while the latter are common are too soft. For these reasons, one has the highest demands on wear resistance solid bodies, such as briquettes made of sintered carbides, instead of structures with welded carbide coatings are used. The extensive use of such bricks however, this is offset by their high price.

The invention shows a way to overcome the difficulties mentioned Avoid and after the spray welding process good coatings containing metal carbide on metallic substrates. The new process enables training such coatings with a high content of hard carbides, with simultaneous damage of the carbide particles by oxidation or diffusion into those forming the auxiliary metal Metal alloy is avoided.

According to the invention, metal powder mixtures containing metal carbide for the production of coatings on metal bodies by spray welding consist of two components, the first of which consists of 10 to 600/0 of a powder of a self-fluxing spray welding alloy with particle sizes below approximately 149 microns and the second component of 90 to 40 % Substantially between 44 and 105 microns in size, produced by sintering or casting and comminuted composite carbide particles consists of particles of tungsten carbide and / or tantalum carbide and / or titanium carbide and / or chromium carbide and / or boron carbide and / or vanadium carbide and / or zirconium carbide and at least 60 / " especially 6 to 25" / "preferably 9 to 1501, an auxiliary metal consisting of nickel and / or cobalt or alloys of these are composed Alloy v is present.

The composite carbide particles are composed of fine carbide particles and grains held together intimately by auxiliary metal. The cohesion of the fine Carbide particles are made by casting or sintering. In the case of the composite carbide particles of the invention are always those produced by casting or sintering Crowds.

The casting or sintering is carried out according to the methods customary in the art performed. For the sintering process, the carbide powder is intimately mixed with a powder of the auxiliary metal, which is preferably used in the same or smaller particle size becomes like the carbide powder. It is then compacted into moldings at at least the temperature corresponding to the softening point of the auxiliary metal, for nickel and Cobalt preferably 1375 to 1510 ° C. The carbide powder should preferably have a particle size below 74 microns should be used, should be expedient both the carbide particles and the parts of the auxiliary metal through sieves with a Mesh size of 2 mm go. It is appropriate to mix the carbide powder with the powder to grind the auxiliary metal in such a way that the auxiliary metal touches the carbide grains before pressing and sintering.

The casting of the carbide composite is expediently done in a molten material Auxiliary metal and form containing carbide particles well mixed with it preferably Temperatures of around 2760 ° C. Carbide particles of approx same particle size as in the sintering process.

After sintering or casting, the pieces or briquettes are comminuted, for example with the aid of crushing rollers or comminuting presses, and reduced to the desired particle size. All composite particles should pass through 105 micron mesh screens, preferably 88 micron mesh screens. On the other hand, the grinding process or removal of fine particles to be controlled so as to not pass more than 1501 particles by sieves with 44 micron mesh size.

For the invention it is not necessary that the auxiliary metal Nickel or cobalt base is in pure form, it can also be waste or suitable Alloys are used provided that the auxiliary metal is its binding and has not lost its cohesive properties. Such products also apply as nickel or cobalt auxiliary metals within the meaning of the invention. After a special Embodiment of the invention, the auxiliary metal itself is a self-fluxing, spray-weldable one Alloy.

At most 1501, the injection-weldable, self-fluxing alloy used in powder form should be smaller than 44 microns. Spray weldable self fluxing alloys are known in the art. They include real alloys or mixtures of self-fluxing alloys with other alloys or non-self-fluxing metals if these powdered mixtures form a self-fluxing alloy when melted. In addition to the actual self-fluxing alloys, this designation also includes mixtures of self-fluxing alloys with other metals or alloys which become self-fluxing during melting.

In general, they contain injection-weldable, self-fluxing alloys at least 30 ° / °, preferably at least 400 / °, nickel or cobalt. As something that makes it flowable Boron is the main element in question. In special cases, good flow properties can be achieved also by phosphorus, lithium or by mixing these two elements with one another or mediate with boron. These metals or the mixtures mentioned can also take the place of boron. Boron is found in the spray weld alloys in general in amounts of 1 to 6 ° / °.

The following is a characteristic self-fluxing alloy based on boron and nickel which is particularly suitable for the invention. Table 2 ° / ° Si .......... 1 to 6 4 to 5 4 to 5 4 to 5 3.5 to 4.5 ° / ° B ........... 1 to 6 3.5 to 4.5 3.5 to 4.5 3.5 to 4.5 3.75 to 4.75 ° / ° Cu ......... 0 to 8 5 to 6 5 to 6 5 to 6 5 to 6 ° / ° Mo ......... 0 to 10 4.5 to 5.5 4.5 to 5.5 4.5 to 5.5 4.5 to 5.5 ° / ° Cr .......... 0 to 20 - 8 to 12 15 to 18 16 to 18 ° / ° C .......... 0 to 1 0 to 0.2 0 to 0.2 0 to 0.2 0.7 to 1 ° / ° Fe .......... 0 to 5 0 to 5 0 to 5 0 to 3 0 to 5 The remainder in all cases nickel.

Table 3 below gives the composition of some characteristic spray welding alloys Plate 3 ° / ° Cr .......... - - 30 to 35 16 to 20 16 to 20 ° / ° Ni .......... 0 to 30 - - 16 to 20 25 to 30 ° / ° Co ......... 30 to 70 60 to 65 42 to 46 35 to 45 35 to 45 ° / ° W .......... 0 to 20 4 to 5 16 to 20 8 to 12 - ° / ° C .......... 0 to 3 0.5 to 1.5 2 to 2.5 0 to 0.4 0 to 0.4 ° / ° Si .......... 0 to 4 - - 2.5 to 4.5 2.5 to 4.5 ° / ° B ........... 1.5 to 4 1.5 to 2.5 1.5 to 2.5 2.5 to 3.5 2.5 to 3.5 ° / ° Mo ......... 0 to 8 - - 4 to. 8 4 to 8 The mixture consisting of the carbide composite particles and the powder of the spray-weldable self-fluxing alloy can be sprayed directly onto the surface to be coated and melted together by the methods customary in spray welding technology.

According to one embodiment of the invention, this mixture is injected onto the surface to be coated and then spray another thin, preferably 50 to 254 micron thick coating made of a carbide-free self-fluxing Alloy. In this process, the outer diffuses out of the self-flowing Alloy existing coating when fused into those made from the mixture Coating, whereby after grinding the covering a top surface of greater density and hardness is obtained.

According to another embodiment, a thin, 50 to 254 micron thick sub-layer of a pure self-fluxing alloy is first sprayed Table 1 Element minimum content maximum content in ° (o in °, 'o Carbon ....... 0.7 1.0 Silicon .......... 3.5 4.5 Boron .............. 2.75 3.75 Iron ............. 3.5 4.5 Cobalt ........... - 1.0 Chromium ........... 16.0 18.0 Nickel ............ remainder remainder Table 2 below shows further spray welding alloys based on boron and nickel which can be used with favorable results for the spray welding process according to the invention. In all tables and in the examples, the quantities given are to be regarded as weight data, unless otherwise stated. of the type of boron-cobalt alloys or boron-cobalt-nickel alloys, which can be used for the invention with very favorable results. onto the surface and only then apply the mixture. Finally, a thin, 50 to 254 micron thick, self-fluxing alloy coating is then sprayed on again. This process allows, on the one hand, the formation of a hard, non-oxidized and dense outer surface, while, on the other hand, a particularly intimate bond between the base and the coating is achieved.

According to the invention, it is also possible to work in such a way that the composite carbide particles are first removed sprayed onto the surface without mixing with spray welding powder and then one approximately 50 to 254 microns thick, made from a self-fluxing spray-weld alloy existing coating is sprayed onto this intermediate layer, whereupon the entire coating mass is applied fuses in the usual way. According to a variant of this working method, you spray in this case, too, initially a self-flowing spray Welding alloy existing coating on the base before the carbide composite particles are applied will.

According to another embodiment of the invention, the auxiliary metal of the carbide composite particles is a self-fluxing spray-welded alloy. In the mixture of self-fluxing alloy and composite particles, only a content of self-fluxing spray-welded alloy reduced by the amount of self-fluxing spray-welded alloy contained in the composite particles is then required. In principle, it is even possible in this embodiment to spray on the carbide composite particles directly without further admixing a special self-fluxing alloy, since the entire amount of self-fluxing alloy can already be present in the form of the auxiliary metal. If the auxiliary metal is not a self-fluxing alloy, it should be present in quantities not exceeding 25%, based on the carbide weight. If the auxiliary metal but a self-fluxing alloy, it can be used in amounts up to about 850 / "are present based on the weight of the Carbidverbundteilchen. If the auxiliary metal has a in quantities of 10 to 850 /" by weight of the Carbidverbundteilchen, present self-fluxing alloy, so The composite particles can be sprayed onto the surface immediately after the usual spray welding process and then fused on site, in which case the special addition of a powder of a spray-weldable self-fluxing alloy can be dispensed with. Preferably, however, the composite particles are mixed with a conventional injection-weldable self-fluxing alloy in powder form or at least one thin coating of the self-fluxing alloy in a thickness of 50 to 254 microns is injected before and / or after the injection-molding of the composite particles and before fusing.

The melted masses are melted in the usual way, for example with the help of a burner, especially one working with acetylene Welding torch. One can also fuse with the spray gun itself, whereby the supply of the powdery spray welding compound or in the form of a welding wire or welding rod supplied mass is interrupted. Finally you get flawless fused coatings also in corresponding melting furnaces. The merging is generally carried out at temperatures between 1040 and 1260 ° C.

If you use a spray-weldable, self-fluxing nickel alloy that contains boron and silicon, it is best to fuse at temperatures between 1065 and 1120 ° C.

The coatings are applied to suitable metal bases, for example to those made of steel or steel alloys.

It has been found that adherence to a very specific Content of auxiliary metal in the carbide composite particles and a very specific particle size these composite particles for the formation of a high quality coating and one high application effects are of decisive importance. Carbide composite particles, whose individual particles are larger than 105 microns have a strong drop in the Performance of the application result. When adhering to the invention Particle size requirements are a high application yield of 900/0 and more achievable. Considering the high cost of carbides, these make up yield the process is only economically viable.

The coatings produced according to the invention are distinguished by their uniformity Distribution of the carbide particles in the auxiliary metal. The entrapped carbide particles are hard, with a relatively sharp demarcation from the auxiliary metal and show very little, if any, diffusion or solid solution of the carbides in the auxiliary metal and no oxidation or other damage to the carbide particles. As a result of these advantages, coatings with superior physical properties are obtained and better wear resistance than the known methods. When comparing with those coatings that have been produced by known welding processes, for example those in which the auxiliary metal was first formed into a hollow rod, in which a core of carbide particles has been introduced, or in which one has cast Welding rods or solid, sintered carbide shaped pieces always resulted a superior wear resistance of the coatings produced according to the invention.

The following examples illustrate the invention; so far unless stated otherwise, all quantitative data are to be regarded as weight data.

Example 1 First, 80% of a sintered tungsten carbide powder was mixed with 20% of a self-fluxing alloy of the following composition: element Weight percent Carbon ....................... 0.8 Silicon ......................... 4.0 Boron .............................. 3.0 Iron ............................ 4.0 Chromium .......................... 17.0 Nickel ........................... rest Virtually all of the carbide powder passed through 88 micron mesh screens while, on the other hand, it was essentially retained by 44 micron mesh screens. The individual particles of this powder of sintered carbide mass were composed of smaller carbide particles which had been coated with cobalt and mixed in such a way that a mixture containing 120% cobalt, the remainder tungsten carbide, was present. This was then sintered into bricks, which were then crushed and sieved off. The self-fluxing alloy was used in the form of a powder, the particles of which passed virtually entirely through 125 micron mesh screens, while only about 100 /, were retained by 44 micron mesh screens.

This mixture produced according to the invention could be with the usual, spray devices used for spraying hot melt materials, a coating was formed, which then becomes a hard, wear-resistant, fused dense layer, which consisted of carbide particles in the cobalt auxiliary metal and embedded in the self-fluxing alloy. Example 2 In one with steel balls 6.3 mm diameter grinding drum equipped with a fine, through Sieves of 44 micron mesh size -through-it tungsten carbide powder with finely powdered Grind cobalt metal until the whale fiber carbide particles are at least partially were coated with cobalt and a mixture was present, the 10% cobalt, the remainder tungsten carbide, contained.

This mixture was then pressed into moldings in small molds and then sintered in a hydrogen furnace at about 1482 ° C. The sintered together Moldings were then comminuted and sieved in such a way that a powder was obtained, its Particles essentially completely through 88 micron mesh sieves while only 5% went through 44 micron mesh screens.

The sintering powder was then mixed with the powder of a self-fluxing alloy in such a way that the mixture contained 80 ″ of the sintered carbide powder (including the cobalt contained therein) in addition to the remainder of the self-fluxing alloy. The admixed self-fluxing alloy had the following composition: element Weight percent Carbon '...................... 0.8 Silicon ......................... 4.0 Boron ............................. 3.0 Iron ............................ 4.0 Chromium .......................... 17.0 Nickel ........................... rest Essentially all of the powder of this self-fluxing alloy passed through 125 micron mesh screens while only 15% passed through 44 micron mesh screens. The powders of sintered carbide mass and self-flowing alloy were intimately mixed with one another and then fed to the storage container of a spray gun suitable for spraying on heat-meltable substances. The mixture was sprayed onto a mild steel plate until a coating about 1 mm thick was formed. Then the mixture of self-fluxing alloy and sintered carbide mass was removed from the metal powder storage container of the pistol and this was charged with the powder of a pure, self-fluxing alloy, the composition and particle size of which are listed above. The self-fluxing alloy was then sprayed onto the intermediate layer to a thickness of about 0.1 mm.

The covering was then placed on the steel plate with the help of an oxygen-acetylene burner heated to 1093'C and held at this temperature for a few moments to achieve the to bring self-fluxing alloy to 'fuse. After that there was a dense relatively non-porous melt layer formed, the hard tungsten carbide particles embedded in the auxiliary metal. The auxiliary metal consisted of one Share of the cobalt present in the sintered carbide and from the self-fluxing carbide Alloy together. If desired, the overlay can be re-grinded Sintered carbide or diamond grinding wheels are used. Example 3 a fine powder of tungsten carbide was intimately melted at about 10 percent by weight Nickel mixed and cast in molds to form bricks. These -were -in shredding rollers crushed and then sieved to particle sizes between 88 and 44 microns brought. The obtained powder of composite carbide particles was mixed with the powder as a Injection-weldable, self-fluxing alloy mixed, .Its particle size was between 125 and 44 microns. The mixture consisted of 75% carbide particles. The powder was poured into a welding rod made of low-melting-point polyethylene introduced, and with a wire spray gun of conventional design on a mild steel plate sprayed on. After the coating had been sprayed on, it was removed with the aid of an oxygen-acetylene torch Heated to about 1093'C until the alloy melted. It had changed after that a -dense, relatively non-porous enamel layer is formed, which consists of hard, tungsten carbide particles embedded in the auxiliary metal.

Example 4 The procedure of Example 2 was repeated, however instead of tungsten carbide now titanium carbide, tantalum carbide, chromium carbide, boron carbide, Vanadium carbide and zirconium carbide are used. In addition, test series were carried out, in which mixtures of these carbides with each other or with tungsten carbide applied became. Flawless coatings were obtained in all cases.

Example 5 In a ball mill, fine tungsten carbide powder (particle size below 15 microns) was ground with the fine powder of a spray-weldable, self-fluxing alloy containing 0.8 "/ 'carbon', 40 /, silicon, 3" /, boron, 4% Contained iron, 170 / chromium and the remainder nickel. The ground material was ground to a fine powder mixture consisting of 300/0 of the self-fluxing alloy, the tungsten carbide particles being at least partially enclosed by the particles of this alloy.

The powdery mixture was then pressed into moldings and sintered in a hydrogen furnace at temperatures of about .1066 ° C. After cooling, it was crushed so that 88-48 micron particles could be sieved off. The powder was then sprayed onto a steel plate with a powder spray gun to a thickness of about 127 microns. This was then brought to 2000 ° C. with the aid of an oxygen-acetylene burner, so that the sprayed-on coating melted together.

After melting, there was a dense, relatively non-porous layer originated in which the hard tungsten carbide particles embedded in the auxiliary metal lay.

Example 6 The powder of the composite carbide particles of Example 2 was made before adding a self-flowing alloy with a conventional spray gun sprayed onto a steel plate. Then that described in Example 2 was self-fluxing alloy sprayed onto the intermediate layer formed, whereupon finally the entire coating at about 1093 ° C with the help of an oxygen-acetylene flame was melted together. After melting it had become part of his Properties of the Coating corresponding to Example 2 educated.

Example 7 Example 16 was repeated, but instead of titanium carbide of tungsten carbide is used. The coating produced contained embedded auxiliary metal Titanium carbide particles, it had excellent density and was proportionate non-porous. Similar favorable results were obtained using tantalum carbide, Chromium carbide, boron carbide, vanadium carbide or zirconium carbide can be obtained.

Example 8 A fine powder of tungsten carbide which passed through 44 micron mesh screens was ground for about 3 hours with a powder of impure nickel metal so that the carbide particles were covered by the nickel. The mixture was adjusted to a nickel content of 1111/0, the remainder being tungsten carbide. It was then pressed into moldings, which were then sintered in a hydrogen furnace at about 1482 ° C. After the briquettes had been comminuted in a press, the mass was sieved off and a powder with individual particles 44 to 88 microns in size was collected. This powder was then mixed with the powder of a self-fluxing alloy to a 820 /, the sintered composite residual self-fluxing alloy containing mixture. Particle size of the self-fluxing alloy: 44 to 125 microns. Composition: 340 /, chrome, 45 % cobalt, 17% tungsten, 20 /, carbon, 2 per cent boron. The powder mixture was then placed in the reservoir of a powder spray gun, sprayed onto a steel plate to a thickness of about 1.27 mm, and then melted together at about 1093 ° C. This procedure resulted in a uniform, non-porous, fused-together layer in which the hard tungsten carbide particles were embedded in the auxiliary metal.

Example 9 Example 8 was repeated, but instead of the nickel powder Cobalt powder used. In further experiments, nickel powder or cobalt powder was used applied in the form of self-fluxing, spray-weldable alloys, their composition can be found in tables 1, 2 and 3. Simultaneously in these experiments as carbides titanium carbide, tantalum carbide, chromium carbide, boron carbide, vanadium carbide, zirconium carbide and mixtures of these carbides with one another or with tungsten carbide are used. In Comparably good results were obtained in all cases. Also let themselves be with all mixtures given in Tables 1, 2 and 3 get good results, if you use this instead of the self-flowing, spray-weldable powdery Applied alloys.

Claims (6)

Claims: 1. Metal carbide containing metal powder mixture for the production of coatings on metal bodies by spray welding, consisting of two components, of which the first consists of 10 to 600 /, a powder of a self-fluxing spray welding alloy with particle sizes below about 149 microns and the second component of 90 to 400 /, essentially between 44 and 105 microns in size, produced and comminuted by sintering or casting, consisting of particles of tungsten carbide and / or tantalum carbide and / or titanium carbide and / or chromium carbide and / or boron carbide and / or vanadium carbide and / or Zirconium carbide and at least 6%, in particular 6 to 25%, preferably 9 to 15%, of an auxiliary metal consisting of nickel and / or cobalt or alloys of these are composed. 2. metal powder mixture according to claim 1, characterized characterized in that the composite carbide particles are substantially between 44 and 88 microns. 3. metal powder mixture according to claims 1 and 2, characterized characterized in that the composite carbide particles contain tungsten carbide as the metal carbide. 4. metal powder mixture according to claims 1 to 3, characterized in that the auxiliary metal is replaced by 10 to 850 /, a self-fluxing spray welding alloy in the second component. 5. Process for the production of coatings Metal bodies by spray welding using a metal carbide containing Metal powder mixture according to claims 1 to 4, characterized in that before and / or after spraying the mixture, a thin coating of a carbide-free one self-fluxing spray welding alloy, preferably in a thickness of 50 to 254 microns, is sprayed onto the surface. 6. Modification of the procedure after Claim 5, characterized in that first the carbide composite particles and on this then the self-fluxing spray welding alloy, preferably in one thickness from 50 to 254 microns. Considered publications: German patent application A 14180 VI / 48 b (published on September 17, 1953); Austrian U.S. Patent No. 177,261.