DE1295855B - High temperature resistant materials and molded parts in dispersion form - Google Patents

Description

High-temperature-resistant dispersions of heat-resistant, non-metallic Substances in metals (dispersion-hardened materials) are of various types known. For example, German patent specification 764 144 describes a method for the production of hard supports for knives, cutting tools and other tools known, according to which a suspension of metal carbides, nitrides or borides and optionally an auxiliary metal on the surfaces subject to wear on tools and the object is sintered on it by heating.

The well-known high-temperature-resistant materials and molded parts in dispersion form however, do not meet the requirements of many cutting tools and components that are resistant to corrosion, Must be erosion and heat resistant, made requirements, so that a need consisted of particularly high-quality materials.

The invention now relates to high-temperature-resistant materials and Molded parts in dispersion form, especially for cutting, grinding, shaping, drilling or Punching tools, electrodes, compression molds, thread guides, bearings and seals, consisting of from 1 to 50 percent by volume iron, cobalt, nickel and / or their alloys with chromium, Tungsten, molybdenum or manganese, the remainder 50 to 99 percent by volume non-metallic phase from 5 to 99 volume percent titanium nitride, aluminum nitride, niobium nitride, vanadium nitride, Zirconium nitride, tantalum nitride and / or hafnium nitride, with the nitride up to 95 O / o by beryllium nitride, boron nitride, thorium nitride, uranium nitride, titanium boride, zirconium boride, Cerium nitride, tungsten carbide, molybdenum carbide, chromium carbide, titanium carbide, zirconium carbide, Tantalum carbide, niobium carbide, zirconium oxide, magnesium oxide and / or thorium oxide replaced and 1 to 95 volume percent of a heat-resistant aluminum compound with a melting point above 1200 ° C and a heat of formation of more than 10 kcal per gAtom of aluminum at 298 ° K, with the non-metallic phase at least 5 percent by volume titanium nitride, aluminum nitride, niobium nitride, vanadium nitride, zirconium nitride, Contains tantalum nitride and / or hafnium nitride.

The high temperature-resistant materials and molded parts according to the invention in dispersion form are extraordinarily hard and firm and show an extraordinary quality Resistance to chemicals, thermal deterrence, shock and high temperatures. They have high electrical and thermal conductivity and offer excellent resistance to erosion. They are as components, for corrosion and erosion resistant equipment of chemical processes, for High temperature electrodes, compression molds, thread guides, bearings and seals and useful for a variety of other purposes in which refractory fabrics are commonly used be used. In the form of tool drills and cutters and cutting tools, which are used for cutting, grinding, shaping, drilling and punching very hard metals or alloys are used, show these dispersion-hardened materials great resistance to wear and pitting, and they are resistant to welding on workpieces even when they cut i at high speed.

The ones used for the materials and molded parts according to the invention Metals can be obtained commercially or prepared in the usual way. the Nitrides can be used in combination with one another or in mixtures with other stable, heat-resistant connections are used.

Suitable heat-resistant aluminum compounds are, for example Aluminum oxide, aluminum nitride, aluminum carbide, aluminum oxycarbide and the aluminum oxide spinels. Other aminides, including those of titanium, zirconium, tantalum, hafnium, Vanadium, niobium, nolybdenum, and tungsten, are like the intermetallic compounds of aluminum with iron, cobalt and nickel for the manufacture of the invention Materials and molded parts can be used.

The dispersions according to the invention are produced by the intimate mixing of the nitride, the heat-resistant aluminum compound or their precursors with the to be used metal each mixed in the form of very fine particles until one homogeneous dispersion is achieved. This homogeneous powder can then be heated and pressed into the desired shape and to the desired degree of density.

The preparation of the powder dispersions is very important because the extraordinary Properties of the heat-resistant dispersions produced therefrom largely depend on the composition of the powder. For example, the homogeneity the common dispersion of the metal, the heat-resistant aluminum compound and the essential nitride, the final particle and crystal size of the nitride, the heat-resistant aluminum compound and the metal as well as the proportional ones Amounts of the metal, the refractory aluminum compound and the nitride are important to achieve the desired properties in the heat-resistant dispersions and are largely determined by the powder used to make the heat-resistant Dispersion is used.

When the powder dispersed together to form very solid heat-resistant compositions, for example for cutting tools and drills, are to be used, it is preferred that the mean particle size of the ingredients is less than 1 micron. Such a particle size increases the strength, Toughness and abrasion resistance achieved with the heat-resistant dispersions can be considerable.

Heat-resistant dispersions can be made from powdery joint dispersions of nitride, heat-resistant aluminum compound and metal are formed, which ranges from about 1 to about 99 parts by volume of nitride per part of metal are located.

A preferred amount of nitride in the powder dispersions is between 3 and 50 parts by volume per part of the metal. A limit on the amount of nitride to less than 30 parts by volume increases the likelihood of continuity of the Metal within the refractory dispersion to be formed and thereby the probability for exceptional impact resistance, strength, toughness and the like, vice versa ensures the presence of at least 3 parts by volume of nitride per part of the metal hardness, abrasion resistance, chemical resistance and the like in the powder. in a heat-resistant dispersion produced therefrom, which the same for such heat-resistant applications, such as cutting tools and drill, make it extraordinarily expedient.

The composite dispersions of the invention can be from about 1 to about 95 volume percent of the refractory aluminum compound, based on the volume of the non-metallic components. Amounts less than 10/0 tend to have a reduction in oxidation resistance and other improved To effect properties of the heat-resistant dispersions. The shares can Do not exceed 95% as the dispersions are at least 5% of any of the essential Nitrides must contain in order to form a nitride bond of the contiguous non-metallic Phase to ensure.

A preferred amount of the refractory aluminum compound is between about 5 and about 50 percent by volume, based on the volume of the non-metallic Components. Such amounts represent the greatest improvement in oxidation resistance and resistance to welding, pitting and seizing Safe cutting tools, which are made from the heat-resistant dispersions according to the Invention are made. It is more preferred to use heat-resistant aluminum compounds to use which are very hard and high melting point, such as aluminum dioxide and Aluminum nitride when the final use of the heat-resistant dispersion takes place in cutting tools or drills.

A preferred embodiment of the invention is a powder dispersion, in which the nitride particles are separated from each other by metal particles. this prevents or reduces the agglomeration or agglomeration of the individual nitride particles during the preparation of the heat-resistant dispersions.

Another preferred embodiment is a dispersion, in which individual nitride particles are uniformly dispersed in the metal, which exists as a continuous phase or a continuous structure and the individual Nitride particles separate from each other. Such a distribution of the metal usually results greatly improved mechanical properties in a heat-resistant dispersion.

Yet another preferred embodiment is a heat resistant one Dispersion, in which a limited amount of interconnection in a continuous Structure or network of the nitride and metal phase according to the invention is present. With such a structure, the nitride phase and the metal phase are interdependent together, with an interpenetrating network of each phase coexisting is. In such dispersions, it is preferred that the individual crystallites of interpenetrating networks are very small and distinguishable, although they are are connected to each other. The heat-resistant aluminum connection can be either present in or between these interpenetrating networks be distributed.

It is desirable that the nitride, the refractory aluminum compound and the metal each have a high chemical purity. In particular it is desired, the presence of oxygen, nitrogen, Boron, silicon or sulfur either in unbound form or as a compound with lower free energy of formation per atom than the corresponding oxides, nitrides, Borides, silicides or sulfides of iron, cobalt, nickel or their alloys too avoid. Other such elements in a form or in amounts specified during react with the metal used during the production of the heat-resistant dispersions or would dissolve in it in such a way that they produce an undesirable brittleness of the Metal should also be avoided. Examples of such Impurities that should be avoided are nickel oxide, iron oxide, cobalt oxide, Chromium oxide and large amounts of free carbon.

Smaller amounts of alloying agents, which are usually mixed with iron, Cobalt and nickel used can be used in the dispersions as long as they are in homogeneous solution with the metal, which is the crystal structure of the Metal owns, are held. Elements such as chromium, tungsten, molybdenum, manganese and others can be used in amounts which are 30 percent by weight of the metal not exceed. Molybdenum, tungsten and chromium are the preferred alloying elements, and they form solid solutions with iron, cobalt and nickel, thus improving their mechanical properties.

When extreme hardness in the metal to be used in the dispersion is desired, elements such as aluminum, titanium, boron, silicon and carbon, in small quantities according to normal metallurgical heat treatment practices used to harden these metals by precipitation. From these elements aluminum and titanium are preferred for nickel-based alloys, and carbon is preferred for iron alloys. As stated earlier, the heat-resistant Aluminum compound present in this form and by reaction on the spot made of added aluminum metal with the binding metal iron, cobalt or nickel be.

When the nitrides are used in combinations with each other, will often found that different interactions occur between the nitrides. This can be solid solutions, mixed nitride compounds or combinations the same form. It is noted that the object of the invention is achieved when these interactions take place, and also in those cases in which the individual Nitrides remain in their original, discrete forms. In terms of properties of the common dispersions obtained, such as abrasion resistance, mechanical properties and heat resistance properties behave simple mixtures, solid solutions and mixed nitride compounds all alike by adding them to the compositions grant extraordinary properties.

Other chemically stable heat-resistant compounds can be used as additives can be used to partially replace the nitride in the dispersions. Such chemically stable nitrides, such as beryllium nitride, boron nitride, uranium nitride, cerium nitride and thorium nitride, can be used to remove some of the aluminum nitride, Titanium nitride, tantalum nitride, vanadium nitride, zirconium nitride, niobium nitride, hafnium nitride or to replace their mixtures. Such stable carbides and oxides, such as titanium carbide, Zirconium carbide, Tungsten carbide, molybdenum carbide, chromium carbide, tantalum carbide, Niobium carbide, zirconium oxide, manesium oxide and thorium oxide can be used in the same manner will. Other compounds, such as the borides of titanium and zirconium, can also be used be used.

However, it is essential that the titanium nitride, aluminum nitride, vanadium nitride, Niobium nitride, tantalum nitride, zirconium nitride, hafnium nitride or mixtures thereof, respectively in amounts of at least 5 percent by volume of the non-metallic phase of the dispersion available. It is generally stated that the heat-resistant dispersions can be improved in proportion to the amount of the essential nitrides which are present are, at least to the point where there is a continuous phase of nitrides is present in the heat-resistant dispersions of the invention. The necessary Criterion to ensure that the continuous nitride phase is present, is explained in more detail below.

It is also essential, as mentioned above, that the heat-resistant Compounds that are used as additives are not those with react to the binding metal in such a way that it becomes brittle or which decompose and brittle components tremble, the presence of which is not permitted for the same reason is.

In general, the one to be followed when choosing these connections The basic idea that their melting point should be above 1600 ° C, while their free energies of formation from the elements forming them should be greater than that free energies of the compounds, which by decomposition of the additional compounds and reactions of the constituent element with the binder metal are formed.

For example, tungsten carbide is a satisfactory additive if it with the nickel or cobalt bonded compositions according to the invention is used because its free energy of formation is the combined free energies of nickel or cobalt carbide and of nickel or cobalt-tungsten alloys, which results from its disproportionation and the reaction of its components with nickel or cobalt, considerably exceeds. In the same way is titanium carbide a suitable additive for an iron-bound composition since its free Formation energy the combined free formation energies of the titanium-iron alloy and the iron carbide resulting from its disproportionation and reaction with the binding metal iron, exceeds.

It is noted, however, that small amounts of additives are included those which react by disproportionation, of the compositions according to the invention are not absolutely excluded. However, if such reactions can occur, it is necessary to limit the amounts of each of these additives to quantities which in the particular composition used in relation to the invention Binder metals are small. This restriction prevents the agglomeration of a Amount of the binding metal which reduce the strength of the heat-resistant dispersion and would make it undesirably brittle.

The amount of refractory additive used in conjunction with or used as a partial replacement for the nitrides essential according to the invention is preferably less than a sufficient amount to be penetrating Network or lattice of addition to form and the formation of a contiguous Network or lattice of the essential nitrides.

The formation of a continuous lattice does not depend solely on the mutual volume fractions of the nitride and the additive, since it is also influenced to a considerable extent by the particle size or crystallite size of the nitride starting powders in relation to the starting powders of the additive particles. If, therefore, coarsely ground particles of the additive, for example particles with a size of 10 microns, are used in conjunction with very finely divided particles of the nitride essential to the invention, for example in the size range from 20 to 100 millimicrons, a thorough network or lattice is formed, which in the is held together essentially by the nitrides according to the invention. This is also true when the nitrides are present in amounts as small as 5% of the non-metallic phase.

As it is generally preferred, additives having a particle size of Using less than 1 micron are slightly larger amounts of the essential nitrides of the order of 20%, the non-metallic phase usually required, to achieve the desired continuity. In the same way it can if the particle size of the essential nitrides to be used is larger than 20 millimicrons the nitrides in as large amounts as 50 percent by volume of the refractory Use phase or above to ensure that the preferred continuous ceramic phase, which is bound by the nitrides according to the invention, is formed will.

It is noted that there are reasons other than desirability the formation of a continuous nitride phase, that is generally quite large amounts of the essential nitrides of the invention in most preferred compositions available. While the mechanism is not entirely clear, it appears that the nitrides according to the invention to an exceptional extent the properties the resistance to welding or sticking to metals that are cut or drilled if the compositions of the invention are used as cutting tips or drill bits can be used, with the ability to form stronger and more stable Combine bonds with the binder metals according to the invention.

A general criterion which is used to form the preferred type of structure, in which a continuous ceramic network or grid of the invention Nitride is formed, is to be followed, is that the product of the volume fraction and the specific surface area of the essential nitrides about the same or preferably greater than the product of the volume fraction and the specific surface area of the additives to be used. Proper attention to this criterion when choosing of the compositions usually gives the preferred type of structure.

Because the structure to some extent also due to the speed the crystal growth that occurs during manufacture is determined it does not need the said criterion in completely rigid Form to apply. Under particularly favorable circumstances, when the rate of growth of the Nitride network under the applied manufacturing conditions the growth rate or the rate of recrystallization of the additive to be used far exceeds, quantities of the essential nitrides according to the invention can be used, which are significantly lower than those corresponding to the criterion just explained, and it becomes the preferred nitride-bonded penetrating ceramic network nonetheless or lattice of the non-metallic phase formed. Manufacture of metals The metals, which can be used in the dispersions according to the invention are iron, Cobalt, nickel and their alloys. A suitable method for making this Metals for incorporation into the dispersions according to the invention is hydrogen reduction of the corresponding metal oxides or carbonates at a temperature of about 600 up to about 1200 ° C.

When making the metals, it is best to use such a low temperature applied as compatible with a reasonably rapid implementation of the reduction is. This is done to avoid excessive sintering and agglomeration of the formed To prevent metal particles.

After the reduction, milling operations are carried out in an inert liquid Medium carried out. In this way, the metal can be obtained in a powder form preferably having a specific surface area of more than 1 m2 / g, whereby it can subsequently be conveniently dispersed with the aluminum nitride. It it is desirable that the grinding media used in the grinding operations be the same Metal like that to be produced, or that they are made of extremely abrasion-resistant Material, such as tungsten carbide bonded with cobalt, insists on potential contamination to make it minimal. Preparation of the nitrides The nitrides to be used according to the invention can be finely ground in any known manner by nitriding the appropriate Hydrides or metallic elements or by suitable reaction in a molten Salt, as described below, can be prepared.

There is a preferred type of production of the nitrides according to the invention in suitable reactions in a molten salt that they too extraordinarily fine particle sizes in the range below 1 micron.

Suitable salts for a salt bath to be used in this reaction may be the alkali halides and alkaline earth halides, especially those which are thermally and thermodynamically stable, like the chlorides and fluorides of sodium, Potassium, lithium, calcium, magnesium and barium.

A second component of the molten salt bath is a halide or oxide of titanium, zirconium, aluminum, niobium, vanadium, tantalum or hafnium. This The component is the metal source for the nitride to be produced.

A stoichiometric amount of alkali or alkaline earth nitride, such as the nitrides of sodium, lithium, calcium, and magnesium, are used in small proportions fed to the weld pool. Gradual addition of the nitride avoids one too violent reaction. The reaction mixture is stirred vigorously while the nitride is added, to ensure a complete response.

The temperature of the reaction should be between the melting point of the salt mixture and 1200 ° C. In general, a temperature of at least 450 ° C is desirable, while a range of 600 to 1100 ° C is most preferred for these reactions will.

The reaction product can be quenched from the molten salt bath the same and dissolving the salt and reaction of the by-products in a solvent which has a high tendency to dissolve the salt and the by-products possesses, but does not attack the heat-resistant nitrides significantly or not quickly. Suitable solvents are distilled water, alcohols and water, mixed with acids such as hydrochloric acid and acetic acid.

If desired, the nitride obtained in this way can additionally be reduced cleaned of broken ammonia in an atmosphere.

In certain cases, the nitrides can be obtained from the molten salt by distilling off the salts and by-products at a temperature of 1100 to 1400 ° C. under a high vacuum. This method avoids exposing the nitride to oxygen, which is why it does not have to be further reduced with ammonia.

In the event that some agglomeration occurs during the synthesis of the nitride occurs, it is possible, for example, by treatment in a Parting ball mill in a non-reactive solvent.

After milling, it may be desirable to add the nitrides, for example to clean by acid treatment to during grinding by abrasion of the grinders to remove absorbed impurities. If desired, a very low one To maintain oxygen levels, the nitride can be broken down in an atmosphere such as Ammonia, to be reduced to any ingested during the cleaning process Remove oxygen.

To avoid the need for cleaning, it is preferred to use a grinding medium, like the balls, made of the same metal as the one with which the nitride should be dispersed. Manufacture of the heat-resistant Aluminum compounds The heat-resistant aluminum compounds can be based on known Ways are made. Process, which the compound obtained in an extraordinarily finely divided form are preferred.

It is generally stated that either the metal aluminides of binder metals according to the invention or those of groups IVB, VB and VIB of the periodic table, especially at high temperature, a certain solubility in the inventive Show binding metals. If the amounts of the compositions according to the invention to be used aluminum compound are very small and are the minimum for the compositions according to the invention required 1 percent by volume approach, a considerable part of the heat-resistant aluminum compound can actually pass into solid solution in the binder metals according to the invention, especially if the production is carried out above the melting point of the binding metal. If it is desired to eliminate these heat-resistant aluminum compounds, can use suitable heat treatment schemes, as are commonly used in metallurgical Practice used to manufacture the precipitation hardened superalloys are used to ensure that the heat-resistant aluminum compounds according to the invention are in particulate form. Preparation of the powder dispersions The common dispersions of metals with heat-resistant aluminum compounds, the nitrides and, if desired, other heat-resistant compounds in the form of a powder represent a preferred embodiment of the invention. The titanium nitride, Aluminum nitride, vanadium nitride, niobium nitride, zirconium nitride, tantalum nitride, hafnium nitride or their mixtures, the heat-resistant aluminum compounds and as required other refractory compounds can be made with the metal powder in any convenient manner Way are dispersed together, for example by mixing in a hydrocarbon solvent or acetone in a colloid mill or a ball mill. Treatment times in the Ball mills from 24 to 500 hours have been found to be satisfactory.

Since the nitride component according to the invention is difficult to clean, it is desirable to have grinders, like the balls, made of the same metal too use such as that with which the nitride is dispersed, or of a material which is extremely resistant to abrasion, such as tungsten carbide bonded with cobalt. The mill can be coated with an elastomeric material such as neoprene, which is not softened or attacked by the grinding media.

After the mixture is milled to homogeneity, the milling media can eliminated by washing out with a suitable solvent such as hexane and taking Vacuum dried. A chemical analysis can be done at this stage be, and if significant amounts of oxygen, carbon or nitrogen with the Metal in any form other than the above-mentioned stable, heat-resistant Compounds are combined, the powders can be reduced to these impurities to remove. This reduction is preferably carried out below 1000 ° C with very dry, pure hydrogen.

The average particle size can easily be determined by examining the dispersed powders together using a light microscope for larger ones Particles and an electron microscope for smaller particles. Under The average particle size becomes the arithmetic mean of the particle diameter Understood. In the case of the preferred powder dispersions, the surface area is per cubic meter Solid from about 3 to 180 m2. The surface per cubic meter can be determined by the specific surface area, measured by normal nitrogen adsorption methods, divided by the density of the solids in the dispersion.

Manufacture of the heat-resistant dispersions The common dispersions metals with nitrides, heat-resistant aluminum compounds and, each if desired, other heat-resistant compounds in the form of a solid substance represent another preferred embodiment of the invention. A representative one Method of forming these dispersions is to make the powder dispersions pressed and heated to almost their theoretical density. The pressing and heating can be done one after the other as in cold pressing and sintering or as in hot pressing, Hot extrusion, hot rolling, hot forging can be carried out simultaneously. That Pressing and heating can be carried out in the presence of a nitrogen atmosphere, if wanted. The preferred manufacturing method is hot pressing.

The pressing temperature depends on the amount of metal used, his State of subdivision and the composition and state of subdivision of the Nitrides. In general, the temperature is at least 1/2 of the melting point, expressed in ° K of the metal component, and should be at least 1000 ° C and not be more than 2000 ° C. The greater the amount of nitride used and the less the pressure applied, the higher the production temperature should be. at Using hot pressing, it is preferred to use a temperature of about 1350 to about 2000 ° C to be used.

Those used for pressing at the highest temperature and below The time required for the full applied pressure changes according to the temperature and the manufacturing process used, as well as the composition and condition the dispersion. In general, the time is between a few seconds for hot extrusion and 1 to 30 minutes for hot pressing and between 10 minutes and a few hours in production by cold pressing and sintering.

The pressure applied also changes according to the temperature and the manufacturing process used, as well as the composition and condition of the dispersion, but usually does not exceed 35.15 at.

Another method of dispersing the ingredients together with each other before making a solid dispersion is that that too metal to be used on previously prepared fine particles of the metal to be used Nitride and the heat-resistant aluminum compound to be used will. The metal can be precipitated, for example, as a hydroxide or aqueous metal carbonate and the resulting homogeneous mixture can then be reduced in an atmosphere that is enriched with nitrogen and hydrogen, for example split Ammonia. This enables the oxides present to be reduced without any change is caused in the nitrides used.

In the same way, an oxide precursor of the nitride to be used, like titanium dioxide as a precursor for titanium nitride, with the hydroxide, the aqueous metal carbonate or the aqueous metal oxide and the desired heat-resistant aluminum compound be precipitated. Then a sufficient Amount of carbon black mixed with the mixed oxide precipitate to form the nitride precursor reduce, and the whole composition can then be brought to a temperature of 1100 to 1500 ° C in split ammonia are heated to an inventive Composition made of nitride, metal and heat-resistant aluminum compound. This composition can, if desired, be ball milled to to dissolve any agglomeration that may have occurred as a result of the heating and reduction.

After a heat-resistant dispersion has been prepared, the particle sizes can the components by making a metallographic cut, etching the Cut with a suitable chemical and examine the surface with a Microscope using an optical microscope or an electron microscope, depending on suitability. When using an electron microscope must, a conventional carbon or plastic negative of the surface is first made and then taking measurements on the negative.

The average particle size of the constituents of a heat-resistant Dispersion according to the invention should not be less than 50 microns. Both In preferred embodiments of the invention, the mean particle size is less than 10 microns, and in the most preferred embodiments of the invention the mean particle size is less than 1 micron.

The type of joint dispersion of the nitride and the heat-resistant Aluminum compound with the metal as well as the dimensions of the metal in the invention Heat-resistant dispersions are a function of the manufacturing conditions and the volume fraction used and the nature of the starting material. A certain Lumping or agglomeration of nitride particles does occur, but as above mentioned, a preferred embodiment of the invention is that most Nitride particles by some sort of continuous metal lattice or structure from one another separated, resulting in a homogeneous and uniform dispersion of each Nitride particles results.

In particular, it is preferred that the homogeneity of the dispersion be such is that the distribution of the nitride and the metal in the refractory dispersion is on a 100 square micron area. This means that a metallographic or an electron micrograph as commonly used in metallurgy Used to study the structure of alloys, both the nitride as well as showing the metal present in a square area, which one is not is greater than 32 microns per edge and preferably no greater than 10 microns each Edge. Further, in the preferred embodiment of the invention, each shows a square area of 10 microns per edge that is examined have essentially the same structural properties like any other such range in the dispersion within usual statistical Distribution limits.

As also noted, is one of the most preferred Embodiments of the invention a heat-resistant dispersion in which a interconnected network or lattice of very finely divided, discrete Crystallites of the metallic phase and the non-metallic phase are present, wherein the constituents of each phase have crystallite sizes or particle sizes of less than 1 micron and wherein the essential nitrides according to the invention are represent the main binding units of the non-metallic phase.

The presence of a continuous phase of the metal in preferred heat-resistant dispersions according to the invention can be determined very easily by measuring the electrical resistivity of the dispersion. Since the heat-resistant connections used according to the invention have a higher electrical Have resistance as iron, cobalt, nickel or their alloys, if the heat-resistant Connections are distributed in such a way that they interrupt the continuity of the metal, so the specific electrical resistance of the heat-resistant dispersion is 10- up to 100 times higher than if the metal were continuous. If the other way around of the metals as a continuous phase over a heat-resistant dispersion according to of the invention is distributed throughout, so is the electrical resistivity the dispersion is inversely proportional to the volume fraction and the thickness of the continuous Conduction path of the metallic component. A noticeable continuity of the metal on a heat-resistant dispersion according to the invention as a whole is through a electrical resistivity of less than about 1 ohm cm displayed, and in the case of the preferred heat-resistant dispersions the specific electrical Resistance less than about 0.05 ohm cem.

It is usually possible by considering appropriately prepared ones to determine metallographic samples of the compositions according to the invention and to show which of these contain the preferred penetrating nitride structure. When the crystallite size of the various components in the heat-resistant Dispersion on the order of 1 micron or greater can exist such a structure or network observed directly in an optical microscope when using 1000X or 2000X magnification. If some or all crystallites of the various constituents are much smaller than 1 micron, the heat-resistant dispersion can be made using conventional methods can be examined by negative electron micrograph method.

The heat-resistant dispersions according to the invention have a density of over 90% of the theoretical density and preferably of over 95% of the theoretical Density. The heat-resistant dispersions which have such uses as cutting tools are to be fed, preferably have a density of over 98% of the theoretical Dense and are essentially free of pores when metallographic Methods are investigated. Theoretical density is calculated by assuming becomes that the specific volumes of the individual components are additive.

The density of the heat-resistant dispersions according to the invention can by any method for the simultaneous determination of weight and volume the composition can be determined. The easiest way to do weight is with a sensitive one analytical balance and the volume determined by mercury or water displacement will.

It is noted that the points discussed the Structure, purity, density, homogeneity and metal continuity of the heat-resistant Dispersions according to the invention in each case to achieve improved properties contribute in such dispersions. The most extraordinary results will however achieved when all these properties are present at the same time. Such heat resistant Compositions in the form of cutting tools or drill bits represent the am most preferred embodiment of the invention.

In such a heat-resistant composition, individual nitride particles, single particles of the refractory aluminum compounds and single particles of other heat resistant compounds, if used, with a medium size of less than 1 micron as a contiguous phase in a continuous Structure of iron, cobalt, nickel or their alloys dispersed homogeneously, see above that the uniformity of distribution over an area less than 100 square microns occurs. The average size of the metal crystals in the composition is less than 1 micron, and the continuity of the metal is such that the composition has an electrical resistivity of less than 0.01 ohm cm. the Amount of nitride and additional refractory compounds, if used, is between 3 and 50 parts by volume per part of the metal, the amount of heat-resistant Aluminum compound is between 5 and 50 percent by volume of the non-metallic phase, and the density of the composition is over 99% of theoretical density. Most preferred metals for this composition are cobalt and one Alloy of nickel with 15 percent by weight of molybdenum. Among the preferred mixes of the refractory compounds is one which contains about 50 to 75 percent by volume of titanium nitride, about 15 to 25 volume percent aluminum nitride or aluminum dioxide and about 8 to 18 percent by volume tungsten car-, bid, based on the volume of the total heat-resistant Phase, contains. For example 118 g finely divided titanium nitride, 24 g finely divided Cobalt and 8.3 g finely divided aluminum nitride are in a steel ball mill with given a capacity of 1.1011 which is 350 g of a high boiling hydrocarbon solvent and 3500 grams of cylindrical ones 6.35 mm long and 3.17 mm in diameter Contains rods made from 94% tungsten carbide with 6% cobalt. The mill then turns 60 Rotated revolutions per minute for 64 hours. The mixture is carried by the oil The decantation is separated and the remaining oil is then washed in Removed hexane in a nitrogen atmosphere. The hexane is then distilled by vacuum removed. The powder obtained contains about 8 parts by volume of titanium nitride and about 1 part by volume Aluminum nitride per part by volume of cobalt.

23 g of this powder are poured into the under a nitrogen atmosphere Bring the mold cavity of a cylindrical carbon mold with a diameter of 2.54 cm, which can be used in the hot area of an induction coil and there is held by two carbon pistons, which in turn with the pressure plates one hydraulic press are connected. The mold and the piston are made by vacuum tight Seals enclosed within a water-cooled, cylindrical steel housing, which is evacuated by a vacuum pump. The temperature control of this system is effected by means of a radiation pyrometer, the output power of which is controlled by a control device operated, which in turn controls the power supply to the induction furnace. To Evacuating the furnace, the temperature of the charcoal mold is raised to 1500 ° C, and a pressure of 281.23 atm is applied. The temperature is then to 1600 ° C will increase and the pressure will continue to be held at 281.23 atm and the sample will held at this temperature for 2 minutes, after which the power is switched off and the Sample is removed from the furnace cavity.

The disc obtained is cut into pieces to examine its flexural strength, their Rockwell A hardness, their density and their performance as a cutting tool for cutting metals and alloys. The average bending strength is 125 kg / mm2, its Rockwell A hardness 91.7 and its density 5.70 g / cms.

Part of the disc becomes a normal cutting tool insert processed and its wear speed and crater depth on a high-performance lathe certainly. The depth of cut is 1.27 mm, the feed is 0.254 mm, and the Speed is 305 m per minute. These conditions are called A-conditions designated. The metal used is 4340 steel.

After 3 minutes of cutting time under the A conditions, there is wear on the flank of this cutting tool only 0.33 mm, and the crater depth is 0.025 mm.

Example2 107.5 g finely divided titanium nitride, 25.2 g finely divided Cobalt and 17.3 g of finely divided aluminum nitride are ground together, and the dry powder is recovered as in Example 2. This powder contains about 7 parts by volume of titanium nitride and about 2 parts by volume of aluminum nitride per part by volume Cobalt.

22 g of this powder are hot-pressed and the disc obtained cut open and examined as in Example 2. The average value of the Bending strength is 87.2 kg / mm2, the Rockwell A hardness is 91.6 and the density 5.75 g / cms.

After 3 minutes of cutting time under the A conditions according to the example 2, the cutting tool insert formed from this disk showed flank wear of 0.406 mm and a crater depth of 0.025 mm.

Example3 96.3 g finely divided titanium nitride, 27.0 g finely divided Aluminum nitride and 26.7 g of finely divided metal alloy, which consists of 90 percent by weight Nickel and 10 weight percent molybdenum are put in a ball mill given and ground as in Example 2, with the exception that the meal 136 Hours. The resulting mixture is then washed free of the oil and dried as in example 2. The powder contains about 6 parts by volume of titanium nitride and about 3 parts by volume Aluminum nitride per volume part of metal.

25 g of this powder are placed in a charcoal mold and as in the example 2 hot-pressed with the Exception that the temperature of the charcoal mold is increased to 1400 ° C and a pressure of 281.23 atm is applied. During this Pressure is maintained, the temperature of the carbon mold is then increased to 1800 ° C and the sample was held at this temperature for 2 minutes, after which the power was switched off and the sample is removed from the furnace cavity.

The slice obtained is cut open and examined as in the example 2. The average flexural strength is 130 kg / mm2, the Rockwell A hardness 91.3 and the density 5.66 g / cms.

A normal cutting tool insert is made from a part of this disc and made on a high-performance lathe under those in the example A conditions examined. Flank wear is this after 3 minutes of cutting time Insert only 0.152 mm, and the crater depth is 0.019 mm. In addition, the Use under a different set of conditions checked, which are called B-conditions The following are designated: The depth of cut is 1.59 mm, the feed is 0.508 mm and the speed is about 90 feet per minute. The cut material is again 4340 steel. Shows after 40 minutes cutting time under the B conditions the insert had a flank wear of 0.101 mm (4 mils) and a crater depth of 0.038 mm (1.5 mils). Example14 120 g finely divided titanium nitride, 22 g finely divided Aluminum nitride, 31 g finely divided cobalt and 27 g finely divided tungsten carbide are ground together as in Example 2 in the ball mill, with the exception that the meal is 99 hours.

The mixture is from the ball mill into a resin kettle of 11 capacity given under a nitrogen atmosphere, and the solids are allowed to settle. Most of the oil is removed by decanting, and the remaining oil is through Eliminated vacuum distillation. The powder obtained contains about 6.4 parts by volume of titanium nitride, about 2.1 parts by volume of aluminum nitride and about 0.5 parts by volume of tungsten carbide per part by volume Cobalt.

25 g of this powder are placed in a charcoal mold and as in the example 2 hot-pressed, with the exception that the temperature of the carbon mold first rose to 1850 ° C is increased and maintained for 11 minutes. A pressure of 281.23 atm is then applied is applied, and the sample is held under this pressure at 1850 ° C for 2 minutes.

The disc obtained is cut as in the example for the purpose of examination. The mean bending strength is 124 kg / mm2, the Rockwell A hardness 90.8 and the density 5.26 g / cms. A normal cutting tool insert is made from one part of the disk and shaped under the A conditions according to Example 2 on a high-performance lathe checked. After 3 minutes of cutting time, the flank wear on this insert was 0.152 mm and the crater depth 0.019 mm. The use was also under the B-conditions investigated according to Example 4. After 15 minutes of cutting time under B conditions the insert flank wear was 0.101 mm and the crater depth was 0.013 mm.

In addition, the use was tested under the following conditions: the speed is about 112.7 m per minute, the cutting depth is 3.17 mm and the feed is 0.762 mm. The cut material is 4340 steel. These conditions are referred to as C-conditions. After 1 minute of cutting under the C conditions, the insert flank wear was 0.101 mm and no crater was formed.

Example: 103 g finely divided titanium nitride, 19.3 g finely divided Aluminum nitride, 49.6 grams of finely divided tungsten carbide and 28.1 grams of finely divided cobalt are ground in the ball mill as in the example, with the exception that the meal Takes 90 hours. The product is separated from the oil by vacuum distillation. The product contains approximately 6 parts by volume of titanium nitride; 2 parts by volume aluminum nitride and 1 part by volume of tungsten carbide per part by volume of cobalt.

25 g of the powder obtained are placed in a charcoal mold and how in Example 2 hot pressed, except that the temperature of the carbon mold first is brought to 1000 ° C and held at this temperature for 3 minutes. the The temperature is then increased to 1850 ° C and the sample at this temperature 5 Held for minutes. A pressure of 281.23 atm is then applied and the sample is kept under this pressure at 1850 ° C for a further 2 minutes, after which the flow switched off and the sample is removed from the furnace chamber.

The disc obtained is cut open for the purpose of testing as in the example. The average flexural strength is 141 kg7mm2, the Rockwell A hardness is 91.3 and the density is 5.98 g / cms.

A normal cutting tool insert is made from a part of this disc Formed and at 4340 steel on a heavy duty lathe under A conditions tested according to example 2. After 3 minutes of cutting time, the flank wear of the Insert 0.152 mm and the crater depth 0.025 mm. Under the C conditions according to the example 5, after 1 minute of cutting time, the flank wear is 0.051 mm and the crater depth 0.013 mm.

The aluminum nitride powder used in the examples can be produced as described below: 40 g of a finely divided gamma aluminum dioxide with a surface area of about 200 m2 / g, which consists of relatively non-agglomerated spheres, are mixed with 400 g of an aluminum flake pigment mixed with an oxygen content of 1.43%. 5.5 g of a dispersion of lithium metal in paraffin wax are added to this mixture, the lithium metal content being about 37%. These are placed in a steel mill with 3.7851, which is 40 percent by volume filled with steel balls. A sufficient amount of an isoparaffinic hydrocarbon solvent with a flash point of 85 ° C is added to cover the steel balls. The filling with steel balls is 9288 g, and 1700 ems of the high-boiling hydrocarbon oil are used. The mill is closed and turned on rollers and runs at a speed of 60 revolutions per minute for 4 days. A sample of about 150 g of this material is separated from the steel balls and the hydrocarbon solvent and placed in a carbon boat and placed in a corundum tube, which in turn is placed in an electric furnace. The temperature is increased to 1450 ° C while maintaining an atmosphere of decomposed ammonia and N2 in the tube for a period of about 3 hours and this temperature is maintained for 2 hours.

The product at this stage consists of a very finely divided one Aluminum nitride powder with a surface area of 6.6 m2 / g and a crystallite size of 210 m # t, measured by X-ray broadening.

After determining the surface area, this material is returned to the carbon boat and heated for a further 8 hours at 1450 ° C. under a nitrogen atmosphere. The chemical analysis shows that it contains 65% aluminum, 2.43% oxygen and 3 0, h% nitrogen. Its surface is 2.0 m2 / g. X-ray line broadening measurements show that this material consists of aluminum nitride with a crystallite size of about 265 millimicrons.

Claims (1)

Claim: High temperature resistant materials and molded parts in dispersion form, especially for cutting, grinding, shaping, drilling or punching tools, electrodes, Compression molds, thread guides, bearings and seals, consisting of 1 to 50 percent by volume Iron, cobalt, nickel and / or their alloys with chromium, tungsten, molybdenum or Manganese, remainder 50 to 99 percent by volume non-metallic phase from 5 to 99 percent by volume Titanium nitride, aluminum nitride, niobium nitride, vanadium nitride, zirconium nitride, tantalum nitride and / or hafnium nitride, the nitride being up to 95% by beryllium nitride, boron nitride, Thorium nitride, uranium nitride, titanium boride, zirconium boride, cerium nitride, tungsten carbide, Molybdenum carbide, chromium carbide, titanium carbide, zirconium carbide, tantalum carbide, niobium carbide, Zirconium oxide, magnesium oxide and / or thorium oxide can be replaced, and 1 to 95 Volume percentage of a heat-resistant aluminum compound with a melting point above 1200 ° C and a heat of formation of more than 10 kcal per gAtom of aluminum at 298 ° K, but the non-metallic phase is at least 5 percent by volume titanium nitride, Aluminum nitride, niobium nitride, vanadium nitride, zirconium nitride, tantalum nitride and / or Contains hafnium nitride.