EP0039791A1 - Method of producing sinterable titanium base alloy powder - Google Patents

Abstract

A process is disclosed for the preparation of alloy powders, which can be sintered and which are based on titanium, by the calciothermal reduction of the oxides of the metals forming the alloys in the presence of neutral additives. This can be accomplished by mixing TiO2 with oxides of the other components of the alloy, admixing an alkaline earth oxide or carbonate with the metal oxides, calcining the mixture. After cooling, the mixture is crushed and calcium is added. Thereafter, green compacts are formed which are heated and leached to remove the calcium oxide. The powder obtained is of uniform structure composition, is free of segrations of oxides nitrides carbides and/or hydrides and has high bulk and tap densities and can be molded by isostatic hot molding.

Description

The invention relates to a method for producing sinterable alloy powders based on titanium by calciothermal reduction of the oxides of the metals forming the alloys in the presence of indifferent additives.

Titanium and titanium-based alloys have found many applications due to their special material properties. Due to the relatively complex manufacturing processes, the alloys of titanium in particular are relatively expensive.

To produce titanium, the naturally occurring oxide is reduced with coal in the presence of chlorine and titanium tetrachloride is obtained, which is processed into the titanium sponge by reduction with metallic sodium or magnesium. The titanium sponge is then, after adding the other alloy components, such as Aluminum and vanadium, melted and cast or rolled into bars, profiles or sheets. The near-contour shaped parts are given their final shape by machining. A disadvantage of this procedure is the sometimes considerable amount of machined alloy. It is therefore not readily possible to produce complicated shaped parts in this way at reasonable prices.

The production of such molded parts is more successful using powder metallurgy. For the production of the alloy Powder, in particular, two methods have become known. One method is characterized in that the titanium sponge is fused together with alloy partners to form a rod-shaped electrode. The electrode is atomized under the action of a plasma flame, and at high speeds in rotation to powder, but because of the dung _B il- of agglomerates as a rule, the powder obtained an additional comminution (grinding up) has to be subjected. However, this so-called REP process is extremely complex, in particular due to the apparatus costs, and moreover is limited to one in terms of the batch weight. limited electrode size.

The second way known for the preparation of the powder consists in hydrogenating the titanium sponge, grinding the brittle titanium hydride, adding the other alloying partners in powder form, intimately grinding, dehydrating at elevated temperatures in vacuo and the powder obtained in a manner known per se pressed and sintered. This process is also complex and cannot satisfy the process.

The invention is therefore based on the object of finding a method for producing sinterable alloy powders based on titanium which does not have these disadvantages. The alloy powders must have a certain grain size and grain size distribution in order to achieve a sufficient bulk density and tapping density. The alloy powders should be uniform, i.e. each powder particle must have the same composition and structure as the other alloy particles. The alloy powders must also be free from precipitates of oxides, nitrides, carbides and hydrides, since otherwise the sinterability is not ensured. Only the sum of the aforementioned properties makes an alloy powder possible for the production of molded parts by pressing and sintering. It should therefore be possible to subject the powders to hot isostatic pressing, which means that it is possible to manufacture near-contour components without complex post-processing.

The invention is in particular the object of producing _L-e gierungspulver such uniformity and purity, that they are useful in the aircraft industry for the production of mechanically highly resistant parts.

From DE-PS 935 456 a process for the production of alloy powders, preferably suitable for the production of sintered bodies by reduction of metal compounds and possibly subsequent removal of by-products, is known, which is characterized in that intimate mixtures of such metal compounds, at least one of which is difficult to reduce , can be reduced with metals such as sodium, calcium. An embodiment of the process is characterized in that the reduction takes place in the presence of indifferent, refractory, easily releasable substances.

The co-reduction of oxides of titanium, copper and tungsten and other oxides is thus described in this patent. In practice, however, the process has found no entry, since no sinterable powders which are homogeneous in their composition and structure could be obtained by this procedure. However, the process described in that patent appeared to have been a potentially appropriate step in the right direction. The method according to the invention is therefore based on this prior art.

• a) Titanoxid mit den Oxiden der anderen Legierungsbestandteile in, bezogen auf Metalle, den der gewünschten Legierung entsprechenden Mengen versetzt, Erdalkalioxid oder Erdalkalicarbonat in einem Molverhältnis von zu reduzierenden Metalloxiden zu _Erdalkalioxid oder Erdalkalicarbonat von 1 : 1 bis 6 : 1 zugibt, das Gemisch homogenisiert, bei Temperaturen von 1000 bis 1300°C 6 bis 18 h glüht, abkühlt und auf eine Teilchengröße < 1 mm zerkleinert,
• b) kleinstückiges Calcium in einer, bezogen auf Sauerstoffgehalt der zu reduzierenden Oxide, 1,2- bis 2,0fachen äquivalenten Menge, sowie einen Booster in einem Molverhältnis von zu reduzierenden Oxiden zu Booster von 1 : 0,01 bis 1 : 0,2 zugibt, diesen Reaktionsansatz vermischt, die Mischung zu Grünlingen verpreßt und in einen Reaktionstiegel einfüllt und verschließt,
• c) den Reaktionstiegel in einen evakuierbaren und beheizbaren Reaktionsofen eingibt, den Reaktionstiegel auf einen Anfangsdruck von 1 - 10^-4 bis 1 - 10^-6 bar evakuiert und auf eine Temperatur von 1000 bis 1300°C für eine Dauer von 2 bis 8 h aufheizt, sodann abkühlt und
• d) den Reaktionstiegel aus dem Reaktionsofen entnimmt, das Reaktionsprodukt aus dem Reaktionstiegel entfernt und auf eine Korngröße < 2 mm zerkleinert, sodann das Calciumoxid mit einem geeigneten Lösemittel, welches das Legierungspulver nicht löst, auslaugt und das erhaltene Legierungspulver auswäscht und trocknet.

Surprisingly, it has now been found that the objects mentioned at the outset can be achieved by a process which is characterized in that

• a) titanium oxide with the oxides of the other alloy components in respect to metals, the desired alloy respective amounts added, alkaline earth oxide or alkaline earth carbonate in a molar ratio to the reducing metal oxides to _E rdalkalioxid or alkaline earth metal carbonate of from 1: 1 to 6: 1 are added, the mixture homogeneous nized, annealed at temperatures of 1000 to 1300 ° C for 6 to 18 h, cooled and ground to a particle size <1 mm,
• b) small-scale calcium in an amount, based on the oxygen content of the oxides to be reduced, of 1.2 to 2.0 times the equivalent amount, and a booster in a molar ratio of oxides to be reduced to boosters of 1: 0.01 to 1: 0.2 admits, mixes this reaction batch, compresses the mixture into green compacts and fills it in a reaction crucible and seals it,
• c) the reaction crucible is placed in an evacuable and heatable reaction furnace, the reaction crucible is evacuated to an initial pressure of 1 - 10 ^-4 to 1 - 10 ^-6 bar and heated to a temperature of 1000 to 1300 ° C for a period of 2 to 8 h , then cools down and
• d) the reaction crucible is removed from the reaction furnace, the reaction product is removed from the reaction crucible and comminuted to a particle size of <2 mm, then the calcium oxide is leached out with a suitable solvent which does not dissolve the alloy powder, and the alloy powder obtained is washed and dried.

The process according to the invention is thus characterized by a combination of special process measures.

According to the aforementioned method according to the invention. thus, in accordance with the desired alloy, the oxides of the alloy partners, based on metal, are first provided in the amounts which correspond to the desired alloy composition. It has been shown in many experiments that direct reduction of these mixtures of the oxides does not produce any sinterable alloy powders, regardless of the pretreatment. Metal powders are formed, some of which can consist of the desired alloy, but also, in uncontrollable amounts, of pure titanium or of the metals or alloys of the others Reaction partners exist. It also contains particles which contain titanium as a base and the other metal components alloyed in different amounts.

These difficulties can be surprisingly overcome by adding certain amounts of alkaline earth metal oxide or alkaline earth metal carbonate to the mixtures of the metal oxides to be reduced and burning them up to form an oxidic multicomponent system, the number of phases of which is smaller than the sum of the starting components (hereinafter referred to as mixed oxide).

According to the invention, the molar ratio of the metal oxides to be reduced to alkaline earth oxide or alkaline earth carbonate is 1: 1 to 6: 1, a range from about 1.2: 1 to 2: 1 is preferred. Calcium oxide or calcium carbonate is preferably used as the alkaline earth oxide or carbonate.

In contrast to the teaching of DE-PS 935 456 cited in the prior art, the alkaline earth oxide, that is to say preferably the calcium oxide, is not added as a desensitizing agent, but rather is used to produce a mixed oxide in which the mixture of the metal oxides to be reduced with the alkaline earth oxide or Alkaline earth carbonate after homogenization at temperatures of 1000 to 1300 ° C, in particular 1200 to 1280 ° C, 6 to 18 h, preferably 8 to 12 h, is annealed. A mixed oxide of reduced number of phases is formed which, after comminution to a particle size of approximately <1 mm, has the same gross composition.

It is particularly advantageous to use alkaline earth carbonate, in particular calcium carbonate, instead of alkaline earth oxide. In the annealing process for producing the mixed oxide, for example, the calcium carbonate cleaves carbon dioxide. Calcium oxide forms with a fresh and active surface. At the same time, the annealed mixed oxide is loosened and can be crushed more easily. The annealing product can be comminuted in a simple manner, for example by means of jaw crushers and subsequent grinding with a cone Mill.

In the second process step, the annealed mixed oxide thus obtained is mixed with small-scale calcium. The calcium should preferably be about 2 mm to 3, in particular have a particle size of about 0. ₅ mm to 8. The amount of calcium is related to the oxygen content of the oxides to be reduced. Based on the oxygen content of the oxides to be reduced, 1.2 to 2.0 times, preferably 1.3 to 1.6 times, the equivalent amount of calcium is used. It takes therefore, for example, per mole, Ti0 ₂ 2.4 to 3.6 mol. Ca, per mole of Al ₂ O ₃ 3.6 to 5.4 moles Ca per mole of V ₂ 0 ₅ 6.0 to 9.0 Mol _C a.

The addition of a booster to the reaction mixture is of particular importance. In metallothermal energy, a booster is a compound that reacts with strong exothermic heat in the metallothermic reduction. Examples of such boosters are oxygen-rich compounds, e.g. Calcium peroxide, sodium chlorate, sodium peroxide, potassium perchlorate. When selecting the boosters, care must be taken to ensure that no compounds are introduced which would interfere with the alloy formation as an unwanted alloy partner. In the method according to the invention, potassium perchlorate has proven itself in a particular way as a booster. A strong exothermic reaction occurs when potassium perchlorate is reacted with calcium. In addition, potassium perchlorate is relatively cheap. A particular advantage of potassium perchlorate is that it is available anhydrous and is not hygroscopic.

The teaching according to the invention of using a booster in the calciothermic coreduction is in direct contrast to the teaching of DE-PS 935 456. There the opinion is held that the reduction would take place with such strong heat that the resulting alloy melt or the resulting one Powder would be very rough. DE-PS 935 456 therefore teaches the reaction in such cases Mix indifferent, refractory compounds, especially oxides. But just the addition of a booster performs process of the invention to alloy powders in which the individual particles each have the same composition and lopf- to achieve a necessary high _K and bulk density have required shape.

The molar ratio of oxides to boosters to be reduced is 1: 0.01 to 1: 0.2, preferably 1: 0.03 to 1: 0.13. The reaction mixture consisting of oxides, calcium and boosters is now mixed thoroughly.

It is possible to add one or more of the desired alloy powders in the form of a metal powder with a particle size <40} to the reaction mixture in stage b). However, due to the problems of a uniform distribution of the added metal powder in the oxide mixture, this is particularly recommended only if the corresponding oxide of the metal sublimates at relatively low temperatures and therefore cannot be annealed together with the other oxides in step a) without loss. An example of such a metal is molybdenum. Molybdenum trioxide sublimates at temperatures> 760 ° C and is expediently added in step b) in the form of a fine metal powder. The mixture is pressed into green compacts. These green compacts are filled into a reaction crucible. It has been shown that a good degree of filling can be achieved, a uniform reaction can be achieved by suitable heat transport and, at the same time, the reduced reaction material can be removed from the crucible without problems if green compacts with a cylindrical shape are used. The green bodies should have a diameter of approximately 50 mm and a height of 30 mm. Deviations from this dimensioning are of course possible.

The green compacts are now filled into a reaction crucible. A reaction crucible is used which is chemically and mechanically stable under the given conditions. Crucibles made from titanium sheets have proven particularly useful.

In the third process step, the reaction crucible is now closed, with a low lumen socket in the closure cover, through which the crucible can be evacuated. The reaction crucible is placed in a heatable reaction furnace and at an initial pressure of about 1. 10 ^-4 to 1. Evacuated 10 ^-6 bar. The _R eak- tion crucible is then heated to a temperature of 1000 to 1300 ° _C. Some calcium distils into the suction nozzle, condenses there and closes the nozzle. Such a self-closing crucible is known for example from DE-AS 11 24 248. A pressure is then set in the reaction crucible which corresponds to the pressure of the calcium at the given temperature. The calcium which is removed from the equilibrium during the reaction and is bound as an oxide can be neglected, since the replication of the gaseous calcium takes place faster than the path reaction. The reaction crucible is left at the reaction temperature for about 2 to 8, preferably 2 to 6 hours.

In a special embodiment of the method according to the invention, the gaseous potassium formed during the reduction of the potassium perchlorate used as a booster and which passes through the evacuation port before the reaction vessel is sealed by condensing calcium is absorbed in an intermediate vessel which is filled with silica gel.

Surprisingly, it has been shown that the gaseous potassium is taken up by the silica gel in a form that the potassium-laden silica gel can be safely handled in the air. If you put the silica gel so loaded in water, hydrogen evolves slowly and over a longer period of time, so that the metallic potassium can be safely collected and removed in this way.

During the reaction period, the booster, especially the potassium perchlorate, is reduced. In addition to metallic potassium, calcium oxide and calcium chloride are formed. The heat released in this way reduces the reduction of the metal oxides favored and accelerated. It occurs in and after the desired _R alloying e-production a. The melting temperature of the alloy, which is surrounded on all sides by calcium oxide, is briefly exceeded. Supported by the molten calcium chloride and under the influence of the surface tension, the alloy particles form in the desired shape of an approximate spherical shape.

In the last stage of the process, the reaction crucible is then removed from the furnace, the crucible is opened, the reaction product is removed from the crucible and comminuted to a particle size of <2 mm. The calcium oxide is treated with a suitable solvent, especially dilute acids, e.g. diluted acetic acid or dilute hydrochloric acid, or complexing agents, such as ethylenediaminetetraacetic acid, leached. The remaining alloy powder is washed neutral and dried.

• der Stufe a): Abkühlen der geglühten Oxidmischung, Zerkleinern der geglühten Oxidmischung,
• der Stufe b): Mischen des Reaktionsgemisches, Verpressen des Reaktionsgemisches zu Grünlingen, Einfüllen der Grünlinge in den Reaktionstiegel,
• der Stufe c): Einbringen des Reaktionstiegels in den heizbaren Ofen,
• der Stufe d): Entnehmen des Reaktionstiegels aus dem Reaktionsofen, Entfernen des Reaktionsproduktes aus dem Reaktionstiegel, Zerkleinern, Auslaugen, Trocknen des Reaktionsproduktes.

It has proven to be advantageous to carry out one or more of the process steps under a protective gas atmosphere. Argon in particular is used as the protective gas. A particularly preferred embodiment of the process according to the invention is therefore characterized in that one or more process steps are carried out under a protective gas atmosphere, in particular one or more of the process steps

• stage a): cooling the annealed oxide mixture, comminuting the annealed oxide mixture,
• stage b): mixing the reaction mixture, pressing the reaction mixture into green compacts, filling the green compacts into the reaction crucible,
• stage c): introducing the reaction crucible into the heatable furnace,
• stage d): removing the reaction crucible from the reaction furnace, removing the reaction product from the reaction crucible, comminuting, leaching, drying the reaction product.

If the reduced reaction product obtained in process step c) contains hydrogen in an impermissible amount, it is advisable to use the reduction product of a vacuum treatment at ₁ . Submit 10- ⁴ to 1 · 10 ^-7 bar at a temperature of 600 to 1000 ° C, especially 800 to 900 ° C, for a time of 1 to 8 h, preferably 2 to 3 h.

Due to its particle size and particle size distribution, the alloy powder obtained according to the invention has the required tap density of about> 60% of the theoretical density. Knock densities of up to almost 70% of theory are achieved. The examination of the alloy powders by microscopic micrographs and with the microsensor prove a uniform composition of each of the alloy particles. They are free of excretions which impair the sinterability or would reduce the mechanical strength of the molded bodies obtained by hot isostatic pressing.

With the method according to the invention, the properties of the standard alloys examined, e.g. TiA16V4; TiA16V6Sn2; TiAl4Mo4Sn2; TiAl6Zr5Mo0.5Si0.25; TiA12V11.5Zr11Sn2; TiA13V10Fe3; manufacture flawlessly.

The particular advantages of the process according to the invention additionally consist in the fact that the raw materials, namely the oxides of the metals, are available in practically unlimited quantities. Apart from their cleaning, they do not require any special processing. By selecting the type and amount of the metal oxides to be reduced, the alloys in the desired composition can easily be produced. The yields in the process according to the invention are very high (> 96%), since no loss-making intermediate steps, as in the process of the prior art, are required are. The method according to the invention is therefore particularly inexpensive. The expenditure on equipment is kept to a minimum. The reproducibility of the alloys produced according to the process is great. The sinterable alloy powders can be produced directly from naturally occurring, purified raw materials while avoiding remelting processes.

The process according to the invention is explained in more detail with reference to the following examples.

example 1 Production of a TiA16V4 alloy

1377.10 g Ti0 ₂ , 85.63 g A1203, 65.60 g V ₂ 0 ₅ and 1601.20 g CaCO ₃ are mixed homogeneously and annealed at 1100 ° C for 12 h. The annealed mixed oxide is crushed to a grain size of <1 mm using a jaw crusher and a cone mill and has the following grain distribution curve: (w / o = weight percent)

The bulk density is approx. 1.40 g / cm ³ and the tap density is approx. 2.30 g / cm ³ . After annealing, the yield of mixed oxide phases amounts to 2418.0 g ≅ 99.7%.

1000 g of this mixed oxide are mixed homogeneously with 1070.6 g Ca and 91.40 g KClO ₄ (≅ 0.08 mol KC10 _{4 /} mol alloy powder) and green compacts with the dimensions of 50 mm diameter and 30 mm height are produced therefrom. At closing these green compacts are 8 _b at a temperature of 1150 ° C hour and at an initial pressure of 1 x 10 ^-5 reduced titanium crucible, after reduction to a particle size ar. <2 mm crushed, leached, the reaction product with dilute hydrochloric acid, which Alloy powder obtained vacuum-treated and dried. The yield of alloy powder is approx. 361.0 g ≅ 95.6%, based on the theoretical yield.

The alloy powder obtained has a bulk density of 1.96 g / cm ³ ≅ 44.95% and a tap density of 2.56 g / cm ³ = 58.6% of the theoretical density.

The grain distribution curve has the following composition:

The chemical analysis of the alloy powder shows the following composition:

The metallographic examination of the alloy powder shows that structurally homogeneous alloy particles are present, the microstructure being from lamellar to fine-globular assign. A homogeneous distribution between a high a and a low ß content can be seen in the alloy.

Example 2 Production of a TiAl6V4 alloy

For a second alloy 1377.10 g TiO _2, 85.63 g A _l2 O _{3, 65, 60} g _V2 0 ₅ and 644.9 g MgO mixed homogeneously and about annealed hours at 1250 ° C and the resulting 12 annealed oxide treated as in Example 1.

After comminution, the mixed oxide has the following particle size distribution:

The bulk density of the comminuted mixed oxide is approximately 1.33 g / cm ³ , the tap density is approximately 1.97 g / cm ³ . After the annealing, the mixed oxide is obtained with a yield of 2154.9 g ≅ 99.16%.

895 g of the mixed oxide are intimately mixed with 1290 g Ca and 133 g KClO ₄ (≅ 0.12 mol KClO ₄ / mol alloy powder), annealed at 1100 ° C. for 12 hours and treated as in Example 1.

The yield of titanium alloy powder is 365.5 g, which corresponds to 96.75% of the theoretically possible yield. The alloy powder has a bulk density of 2.14 g / cm ³ ≅ 48.97% and a _K lopfdichte of 2.78 g / cm ³ ≅ 63.76%, based on the theoretical density on.

. The grain distribution curve of the alloy powder has the following composition:

The chemical analysis shows the following composition:

It can be seen from the results of the metallographic examination that the alloy particles have the same structure, which can largely be characterized as lamellar to fine globular. The microstructure also shows that the alloy particles have a homogeneous a and β phase distribution.

Example 3 Production of a TiAl6V6Sn2 alloy

1334.40 g TiO ₂ , 103.90 g Al ₂ O ₃ , 99.3 g V ₂ O ₅ , 45.15 g SnO and 1601.2 g CaCO ₃ are mixed intimately or homogeneously and annealed for approx. 12 h at 1250 ° C. The annealed oxide is crushed using a jaw crusher and a cone mill to a grain size of <1 mm ≅ 1000 µm and has the following grain distribution curve:

The bulk density of the comminuted oxide is 1.63 g / cm ³ and the tap density is 2.58 g / cm ³ . After the annealing, the mixed oxide is obtained with a yield of 2415.0 g ≅ 97.4%.

1000 g of this mixed oxide are mixed homogeneously with 1133.9 g Ca and 129.8 g KC10 ₄ (0.12 mol KClO ₄ / mol alloy powder), compacted, reduced at 1150 ° C. for 8 hours and, as described in Example 1, processed further. The yield of titanium alloy powder is 367.2 g, which corresponds to 96.5%, based on the theoretical yield.

The alloy powder has a bulk density of 2.18 g / cm ³ ≅ 49.3% and a tap density of 2.81 g / cm ³ ≅ 63.45% of the theoretical density.

Die chemische Analyse ergibt folgende Zusammensetzung:

The grain distribution curve of the alloy powder has the following composition:

The chemical analysis shows the following composition:

The metallographic examination shows alloy particles with a homogeneous structure and phase distribution. The microstructure is fine lamellar structure of the a-phase which is stabilized by innzusätze _Z. There are no Ti ₃ Al phases that hinder the non-cutting shaping.

Example 4 Production of a TiAl4Mo4Sn2 alloy

Die Schüttdichte des Mischoxids beträgt 1,84 g/cm³ und die _Klop_fdichte liegt bei ₂,₇₆ g/cm³. Die Ausbeute an verwendungsfähigem Mischoxid liegt bei 2358,0 g ≅ 98,1 % der theoretischen Ausbeute.1439.5 g Ti0 ₂ , 72.5 g Al ₂ O ₃ , 21.8 g SnO and 1601.2 g CaCO ₃ are homogeneously mixed and annealed at 1250 ° C for about 12 h, then the annealed mixed oxide is passed through a Jaw crusher and a cone mill crushed to a grain size of <1 mm. The mixed oxide has the following grain distribution curve:

The bulk density of the composite oxide is 1.84 g / cm ³ and the _{toilet fdichte} p is _{2, 76} g / cm ^3. The yield of usable mixed oxide is 2358.0 g ≅ 98.1% of the theoretical yield.

1000 g of this mixed oxide are mixed homogeneously with 24.90 g Mo powder, 1109.1 g Ca and 115.3 g KClO ₄ , compacted and, as described in Example 1, further treated. The yield of titanium alloy powder is 384.8 g = 96.5% of the theoretical yield.

The alloy powder has a bulk density of 2.39 g / cm ³ ≅ 52.8% and a tap density of 2.88 g / cm ³ ≅ 63.6% of the theoretical density.

The grain distribution curve has the following composition:

The chemical analysis of the alloy powder shows the following composition:

The metallographic examination shows alloy particles with a homogeneous structure. In addition to the stabilized a phase as the main component, there is a small β component in the alloy particles.

Example 5 Production of a TiAl6Zr5Mo0.5Si0.25 alloy

1379.9 g TiO ₂ , 106.3 g Al ₂ O ₃ , 63.3 ^g ZrO ₂ , 10.7 ^g Si0 ₂ and 1601.2 g CaCO ₃ are mixed homogeneously and annealed at 1250 ° _{C. for} 12 hours. The annealed mixed oxide is then crushed to a grain size of <1 mm ≅ 1000 µm using a jaw crusher and a cone mill. The grain ver. Pitch curve has the following composition:

The bulk density of the mixed oxide is 2.12 g / cm3 ≅ 48.11% and the tap density is 2.54 g / cm ³ ≅ 57.65% of the theoretical density. The yield of usable mixed oxide is 2425.0 g and corresponds to 98.7% of the theoretical yield.

1000 g of this mixed oxide are mixed homogeneously with 1.91 g of very fine-grained molybdenum metal powder, 1125.9 g of Ca and 131.2 g of KC10 ₄ (0.12 mol of KClO ₄ / mol of alloy powder) and, as described in Example 1, processed further. The yield of titanium alloy powder is 369.4 g 96.6%, based on the theoretical yield of alloy powder.

The alloy powder has a bulk density of 2.12 g / cm ³ ≅ 48.11% and a tap density of 2.68 g / cm = 60.9 _{% of} the theoretical density.

The alloy powder has the following grain distribution curve:

The chemical analysis of the alloy powder shows the following composition:

Metallographic studies show that structurally homogeneous alloy particles are present, with a pronounced, β-stabilized microstructure which, as is known, gives this alloy higher heat strengths after sintering.

Example 6 Production of a TiAl2V11.5Zr11Sn2 alloy

1245.22 g TiO ₂ , 38.0 g Al ₂ O ₃ , 207.5 ^g V ₂ O ₅ , 149.4 ^g ZrO ₂ , 23.1 g SnO and 1601.2 g CaCO ₃ are mixed intimately or homogeneously and annealed at 1250 ° C for 12 hours. The annealed mixed oxide is crushed using a jaw crusher and a cone mill to a grain size of <1 mm ≅ 1000 µm and then has the following grain distribution curve:

The bulk density of the annealed mixed oxide is 2.415 g / cm 3 ≅ 50.15% and the tap density 3.185 g / cm ³ ≅ 66.2% of the theoretical density. The yield of usable mixed oxides is 2412.2 g, which is 94.2% of the theoretical yield.

1000 g of this mixed oxide are mixed homogeneously with 1640.2 g Ca and 162.3 g KC10 ₄ (0.10 mol KClO ₄ / mol alloy powder) and, as described in Example 1, processed further. The yield of alloy powder is 378.2 g ≅ 95.55% of the theoretical yield.

The alloy powder has a bulk density of 2.68 g / cm ³ ≅ 55.65% and a tap density of 3.13 g / cm3 ≅ 65.1% of the theoretical density.

The alloy powder has the following grain distribution curve:

The chemical analysis of the alloy powder shows the following composition:

The metallographic examination of the alloy powder shows particles with a homogeneous structure and β stabilization. Sintered parts made from these alloys result in components with relatively high fracture toughness.

Example 7 Production of a TiAl3V10Fe3 alloy

1325.2 g TiO ₂ , 55.2 g Al ₂ O ₃ , 168.6 ^g V ₂ O ₅ , ^{39.4 g Fe} ₃ ⁰ ₄ and 1601.2 g CaCO ₃ are mixed homogeneously and at a temperature of 1100 ° C annealed for 12 h. The annealed mixed oxide is then passed through a jaw crusher and a Cone mill crushed to a grain size of <1 mm = 1000 µm. The grain distribution curve then has the following composition:

The bulk density of the annealed mixed oxide is 2.314 g / cm ³ ≅ 49.61% and the tap density 3.012 g / cm ³ ≅ 64.6% of the theoretical density. The yield of usable mixed oxides is 2398.6 g ≅ 96.5. % of theoretical yield.

1000 g of this mixed oxide are mixed homogeneously with 2833.8 g Ca and 147.95 g KClO ₄ (0.12 mol KClO ₄ / mol alloy powder) and, as described in Example 1, processed further. The yield of alloy powder is 360.8 g ≅ 94.8% of the theoretical yield.

The alloy powder has a bulk density of 2.410 g / cm ³ Z 51.7% and a tap density of 2.981 g / cm ³ = 63.9% of the theoretical density.

The measurement of the grain distribution curve of the alloy powder gives the following values:

Chemical analysis of the _L egierungspulvers gives the following composition:

The metallographic examination of the powdery alloy shows particles with a homogeneous structure and a-phase stabilized. Sintered parts made from these alloy powders are said to have a higher creep resistance.

From the examples it can be seen that the alloy powders produced by the process according to the invention contain a typical process content of 0.05 to 0.15% by weight of calcium. However, this amount has no influence on the quality and processability of the alloy powder.

Example 8 Production of a TiA16V4 alloy

1377.10 g TiO ₂ , 85.63 g Al ₂ O ₃ , 65.60 g V ₂ 0 ₅ and 1034.52 g CaO (1: 1) are mixed homogeneously and annealed at 1000 ° C for 18 h. The annealed mixed oxide is crushed to a grain size of <1 mm using a jaw crusher, cone and cross beater mill and has the following grain distribution curve:

The bulk density is approximately 1.45 g / cm. The tap density is 2.28 g / cm ³ . After annealing, the yield is 2605.8 g ≅ 98.7%.

1000 g of this mixed oxide are homogeneously mixed with 1051.62 g Ca (1: 1.2 mol) and 228.50 g KClO ₄ (≅ 0.20 mol KC10 ₄ / mol alloy powder) and green bodies with the dimensions of 50 mm diameter and a height of 30 mm.

These green compacts are then introduced into the reaction crucible, the reaction crucible is inserted into the furnace and the furnace is closed. The reaction chamber with reduction crucible is evacuated to a pressure of <1 × 10 ^-4 bar at room temperature and then heated up to 1300 ° C. and held at this temperature for 2 hours.

After the reduction, the reaction product is comminuted to a maximum particle size of <2 mm, the comminuted reaction product is leached with dilute nitric acid, filtered and washed until neutral. The obtained Le ^g ierungs- powder is vacuum treated and dried. The yield of alloy powder is 363.5 g ≅ 94.8%, based on the theoretical yield.

The alloy powder obtained has a bulk density of ^2.0 3 g / cm ³ ≅ 46.56% and a tap density of 2.69 g / cm ³ ≅ 61.7% of the theoretical density.

The particle size distribution curve of the _L egierungspulvers has the following composition:

The chemical analysis of the alloy powder shows the following composition:

The metallographic examination of the alloy powder shows that there are structurally homogeneous alloy particles with a uniform a and β distribution. The proportion of a in the alloy particles predominates. The development of the individual phases can be classified as fine globular to lamellar.

Example 9 Production of a TiA16V4 alloy

1377.10 g TiO ₂ , 85.63 g Al ₂ O ₃ , 65.60 g V ₂ 0 ₅ and 172.45 ^g Ca0 are mixed homogeneously with one another (6: 1) and annealed at 1300 ° C. for 6 hours.

The annealed mixed oxide is comminuted to a grain size of <1 mm using a jaw crusher, cone and cross beater mill nert and has the following grain distribution curve:

The bulk density of the annealed, mixed oxide phases is 1.58 g / cm ³ and the tap density is approximately 2.48 g / cm ³ . After annealing, the yield is 1665.7 g 97.9%, based on the theoretical yield.

1000 g of this mixed oxide are homogeneously mixed with 1991.80 g Ca and 11.43 g KClO ₄ ( ⁼ 0.01 mol KClO ₄ / mol alloy powder) and green compacts with the dimensions of 50 mm diameter and 30 mm height are produced therefrom.

The green compacts are then inserted into the reaction crucible, the reaction crucible is placed in the furnace and the furnace is then closed. The reaction chamber with the reduction crucible is then evacuated at room temperature to a pressure of <1 × 10 ^-6 bar and then heated up to 1000 ° C. and kept at this temperature for 8 hours.

After the reduction, the reaction product is crushed to a grain size of <2 mm, then leached with formic acid, vacuum-treated and dried. The yield of alloy powder is approx. 358 g ≅ 93.5%, based on the theoretical yield.

The alloy powder obtained has a bulk density of 1.91 g / cm ³ ≅ 43.80% and a _K lopfdichte of 2.76 g / cm ³ ≅ 63.6% theoretical density.

The grain distribution curve has the following composition:

The chemical analysis of the alloy powder shows the following composition:

The metallographic examination of the alloy powder shows that structurally homogeneous alloy particles are present, the microstructure being lamellar to fine-globular. The alloy mainly consists of a high a component and a low β component.

Example 10 Production of a TiAl3V10Fe3 alloy

1325.2 g TiO ₂ , 55.2 g Al ₂ O ₃ , 168.6 g V205, ³ 9, ^{4 g Fe} ₃ ⁰ ₄ and 260.1 g CaO (4: 1) are mixed homogeneously and at 1300 ° C Annealed for 10 hours.

The annealed mixed oxide is crushed to a grain size of <1 mm using a jaw crusher, cone and cross beater mill and has the following grain distribution curve:

The bulk density of the mixed oxide is 1.54 g / cm ³ and the tap density is 2.49 g / cm ³ . After annealing, the yield is 1869.6 g ≅ 99.7% of the theoretical yield.

1000 g of this mixed oxide are mixed homogeneously with 598.8 g Ca (1: 1.5) and 128.5 g KC10 ₄ ( ⁼ 0.05 mol KClO ₄ / mol alloy powder) and green parts with the dimensions of 50 mm height and 30 mm diameter made from it.

These green compacts are then introduced into the reaction crucible and then the reaction crucible is charged into the oven and evacuated to a pressure of <1 × 10 ^-6 mbar at room temperature and then heated to 1200 ° C. The response time is 6 hours.

After the reduction, the reaction product is crushed to a maximum grain size of <2 mm, then leached with dilute hydrochloric acid, vacuum-treated and dried. The yield of alloy powder is 501.8 g ≅ 97.4%, based on the theoretical yield.

The alloy powder produced has a bulk density of 2.43 g / cm ³ ≅ 53.3% and a tap density of 2.978 g / cm ³ ≅ 65.2% of the theoretical density.

The measurement of the grain distribution curve of the alloy powder gives the following values:

The chemical analysis of the alloy powder shows the following composition:

The metallographic examination of the alloy powder shows particles with a homogeneous structure and stabilized a-phase.

Claims (9)

1. A process for the production of sinterable alloy powders based on titanium by calciothermic reduction of the oxides of the metals forming the alloys in the presence of indifferent additives, characterized in that a) titanium oxide with the oxides of the other alloy components in respect to metals, the desired alloy respective amounts added, alkaline earth oxide or alkaline earth carbonate in a molar ratio to the reducing metal oxides to _E rd- alkali or alkaline earth metal carbonate of from 1: adding 1: 1 to 6 the mixture is homogenized, annealed at temperatures from 1000 to 1300 ° C. for 6 to 18 h, cooled and ground to a particle size of <1 mm, b) small-scale calcium in an amount, based on the oxygen content of the oxides to be reduced, of 1.2 to 2 times the equivalent amount, and a booster in a molar ratio of oxides to be reduced to boosters of 1: 0.01 to 1: 0.2 admits, mixes this reaction batch, compresses the mixture into green compacts and fills it in a reaction crucible and seals it, c) the reaction crucible is placed in an evacuable and heatable reaction furnace, the reaction crucible to an initial pressure of 1 10 ^-4 to 1 · 10 ^-6 bar evacuated and heated to a temperature of 1000 to 1300 ° C for a period of 2 to 8 h, then cooled and d) the reaction crucible is removed from the reaction furnace, the reaction product is removed from the reaction crucible and comminuted to a particle size of <2 mm, then the calcium oxide is mixed with a suitable solvent, which the alloy powder does not dissolve, leach and the alloy powder obtained washes and dries. 2. The method according to claim 1, characterized in that in stage a) alkaline earth or alkaline earth carbonate in a molar ratio of metal oxides to be reduced to alkaline earth or alkaline earth carbonate from 1: 1 to 2: 1 is added. 3. The method according to claim 1 or 2, characterized in that in step a) calcium oxide or calcium carbonate is used as alkaline earth oxide or alkaline earth carbonate. 4. The method according to claim 1, 2 or 3, characterized in that one or more of the process steps stage a): cooling the annealed oxide mixture, comminuting the annealed oxide mixture, stage b): mixing the reaction mixture, pressing the reaction mixture into green compacts, filling the green compacts into the reaction crucible, stage c): placing the reaction vessel in the heatable furnace, stage d): removing the reaction crucible from the reaction furnace, removing the reaction product from the reaction crucible, comminuting, leaching, drying the reaction product,
carried out under a protective gas atmosphere. 5. The method according to one or more of the preceding claims, characterized in that the reaction mixture in step b) one or more of the desired alloy partners in the form of a metal powder a particle size of <40 microns. 6. The method according to one or more of the preceding claims, characterized in that in step b) a calcium granulate of an average particle size of 0.5 to 8 mm is used. 7. The method according to one or more of the preceding claims, characterized in that potassium perchlorate is used as the booster. 8. The method according to claim 7, characterized in that the gaseous potassium emerging from the reaction furnace is absorbed in silica gel. 9. The method according to one or more of the preceding claims, characterized in that the reaction product obtained in step c) of a vacuum _treatment at ₁ . 10 ^-4 to 1 · 10 ^-7 bar, a temperature of 600 to 1000 ° C for a period of 1 to 8 h.