DE1245831B - Process for the production of a metal-ceramic composite body - Google Patents

Description

Method for producing a metal-ceramic composite body The invention relates to a method for producing a metal-ceramic composite body, in which the parts to be connected are brought into direct contact with each other and be heated.

There are already a number of methods for producing metal-ceramic composite bodies known in which the components are always connected to one another via a metallic intermediate layer get connected. For example, there is a method in Hungarian patent specification 120 862 described, in which a ceramic containing zirconium oxide, for example Body by brazing using molybdenum powder with a metal body is connected. Similar procedures are in the German Auslegeschriften 1004 989 and 1013 216, but set due to the use of a metallic intermediate layer an essentially equal expansion coefficient of the components of the composite body in advance. In the process, the latter come as metallic components Ausleschrift Titan or Zirconium for use; while the intermediate layer made of a metal or a metal alloy with a lower melting point than zirconium, for example of silver, gold, copper, nickel, iron, cobalt or manganese. Also in the French patent specification 850 831 is a method for connecting of chrome, manganese, iron, cobalt and nickel parts with ceramic parts via one Intermediate layer, which can also consist of zirconium or tautal, for example, described.

It. are also methods for "direct bonding of ceramic and metallic parts known; where as according to the German interpretative document 1001178, "Electronics" c, June 1949, p. 168 and "RCA Review", March 1954, p. 47, which to connecting parts individually or together up to above the melting temperature of a the components are heated and pressed together under high pressure, the joining a metallic and a ceramic body using an intermediate layer or a solder is cumbersome, since the application of the metallic intermediate layer or the soldering requires special measures and devices. Another disadvantage is that the thermal stability of the composite body by the melting point of the intermediate metal is limited and when soldering or applying the intermediate layer there is a risk of electrolytic corrosion. In the rest of the application the known method mostly limited to the use of components, their The expansion coefficients are the same or differ only slightly from one another. Methods are also known in which metallic and non-metallic or ceramic Bodies are connected to one another via a non-metallic intermediate layer. So are in the German patent specification 897 377 and the British patent specification 802 086 method described in which the kermaische and the metallic body brought into close contact with each other and in an oxidizing atmosphere with one at a temperature sufficient for the oxidation of the metal, if necessary under pressure to be annealed. In the case of oxidizing annealing or pressure annealing, it occurs in the temperature range from 500 to 1000 ° C at the interface between the two components of the composite body an oxide layer that fills the parting line and with the two neighboring materials is in close connection. Although the oxidation of one component to one leads to chemical compound formation, it is the aforementioned method always just a physical bond between the two components through diffusion of the metal oxide into the porous ceramic body.

Finally, there is one more from British patent specification 872 930 Process for creating a diffusion bond between metals or ceramics Known substances on the one hand and metals on the other. In this procedure -will those to be connected Bodies brought into close contact with each other, the gap between the contact surfaces is evacuated and sealed. Then will the pre-workpiece in an inert gas atmosphere under high pressure up to temperature the plastic flow of one of the two materials, but always below the Melting temperature of both materials heated. With such pressure heating or pressure sintering diffuses at the temperature of plastic flow located material into the solid body, so that a so-called diffusion connection comes about.

Since the known methods including those mentioned at the beginning Soldering process always focuses on the physical connection of different materials including metals on the one hand and ceramic materials on the other relate, the resulting composite bodies have only a limited thermal Resistance. The object on which the invention is based is therefore a process for producing temperatures up to well above 1200 ° C to create absolutely pressure-tight and thermally resistant composite body. To the solution This task is proposed that tautal or tantalum alloys at 2200 ° C in an inert atmosphere in contact with a ceramic body made of stabilized Zirconium oxide or a mixture of stabilized zirconium oxide with metal oxides like thorium oxide and beryllium oxide is heated until a firm connection of the metal part came about with the ceramic part. - The main advantage of the invention Process is that it is at an annealing temperature of 2200 ° C and normal pressure a connection of the components of the composite body occurs. This interconnection leads to an extraordinary thermal stability of the composite body itself at temperatures exceeding 2000 ° C. This can be explained by the fact that the interface between metal and ceramic material in the formation of the connection almost completely disappears and it when reheated to the temperature of the compound formation or - temperatures exceeding 2000 ° C do not result in any dissolution or destruction of the network can come. This is all the more surprising as the coefficient of thermal expansion of stabilized zirconium oxide is almost twice as large as that of tantalum, so that, according to previous knowledge, there is a connection between the two materials - excluded from the start. Another with the connection formation between the Component of the composite body causally linked advantage of the invention The method is that the composite body is absolutely vacuum-tight while the composite bodies produced by the known method - depending on the respective porosity of one or both components are less vacuum-tight.

Attempts have already been made to use tantalum and zirconium oxide bodies to connect with each other, but the tantalum body first had to be in a vacuum arc be coated with a platinum film. Only then could the two parts go through Soldering together using a silver-copper-zinc alloy as a solder get connected. However, silver melts at around 960 ° C. so that after this Process produced composite bodies at temperatures of 900 to 1100 ° C not are more durable. There have also been attempts to produce metal-ceramic composite bodies using gold and nickel films between the metal and the zirconia not led to a highly heat-resistant composite body, because in the area the boundary layer resulted in a eutectic alloy, which increases the durability of the composite body limited to about 1400 ° C.

The ceramic body containing stabilized zirconium oxide can be made from pure zirconium oxide ZrO2, to which small amounts of various oxides, for example calcium oxide or magnesium oxide, are added. The ceramic body can, however, also be made from Zr02 - Si02 or from zirconia in an electric furnace. Zirlüt contains 70 to 800 /, Zr02 and essentially silica, iron oxide, titanium oxide and aluminum oxide as impurities. The impurities can be separated from the zirconium oxide by reduction with coke or grinding and subsequent mechanical separation of the fired grist. Commercially available stabilized zirconium oxide contains about 5% calcium oxide and has a melting point of about 1427 to 1550 ° C.

, - The stabilized. - Ceramic component containing zirconium oxide can also contain metal oxides in relatively large amounts. For this comes every oxide or mixture of oxides in question, in the cubic stabilized zirconium oxide may be present with tantalum or a tantalum alloy with the formation of tantalum zirconate results in a thermally stable composite body. These mixed oxides include mixtures from cubic zirconium oxide with up to about 23 mol percent thorium oxide or from 75 up to 90 mole percent thorium oxide, remainder zirconium oxide. Also ternary, mixed oxides, for example Mixtures. from over 5 mole percent calcium oxide (based on the mixture), beryllium oxide and zirconium oxide, from up to 10 mole percent magnesium oxide, beryllium oxide and up to 90 Mole percent zirconium oxide and more than 10 mole percent cerium oxide; Beryllium oxide and Zirconium oxide come into question.

The metallic component can be made from Tautal or its alloys, for example with tungsten, rhenium, niobium, molybdenum and other high-melting points and refractory metals. So were with a 10% tungsten Tantalum alloy gives good results.

- Argon and helium are used as the inert gas for the process according to the invention or other noble gases in question.

The invention is described below on the basis of an exemplary embodiment. explained in more detail_ -A ceramic body made of stabilized zirconium oxide and 5.001, calcium oxide, 0.70 /, silicon dioxide, 0.30 /, titanium dioxide, 0.20 /, hematite (Fe203), 2.011 / 0 hafnium dioxide, 0.5% Aluminum oxide and 91.3 l) /, zirconium oxide (all data in percent by weight) were brought into contact with pure Tautal and heated in an induction furnace under an argon atmosphere. The parts to be joined were very quickly brought to about 2000 ° C. , kept at this temperature for about 5 minutes to 4 hours and then cooled to room temperature. Tests carried out with the composite bodies produced in this way showed that the strength increases with the duration of annealing and the connection was still free of defects even after immersion in liquid nitrogen. Likewise, no damage resulted from thermal cycling between room temperature and annealing temperature within short time intervals of 1 to 2 minutes. The X-ray examination revealed an intermediate layer of magnesium tantalate Mg4Ta209, tantalum silicide Ta5Si, tantalum zirconate Ta2Zrs017 and yttrium tantalate YTa04 between the components.

In further experiments were according to the method according to the invention produced composite body with its tantalum component suspended in an inductive field and heated to break. A breaking temperature of 2370 ° C. was measured. Such temperatures can be achieved with the conventional methods Tantalum ceramic connections cannot be achieved. In addition, the composite body according to the invention was still absolutely vacuum-tight even after heating to over 2000 ° C.

Claims (7)

Claims: 1. A method for producing a metal-ceramic composite body, in which the parts to be connected are brought into direct contact and heated, in that tantalum or tantalum alloys are used at 2200 ° C in an inert atmosphere in contact with a ceramic body made of stabilized Zirconium oxide or a mixture of stabilized zirconium oxide with metal oxides, such as thorium oxide and beryllium oxide, is heated until a firm bond of the metal part came about with the ceramic part. 2. The method according to claim 1, characterized through the use of an inert atmosphere containing a noble gas. 3. Procedure according to claims 1 and 2, characterized by the use of a ceramic Body made of cubic zirconium oxide with up to 23 mole percent thorium oxide. 4. Procedure according to claims 1 and 2, characterized by the use of a ceramic Body made of cubic zirconium oxide with. 75 to 90 mole percent thorium oxide. 5. Procedure according to claims 1 and 2, characterized by the use of a ceramic Body consists essentially of over 5 mole percent calcium oxide, beryllium oxide and zirconium oxide. 6. The method according to claims 1 and 2, characterized by the use of a ceramic body consisting essentially of up to 10 mol percent magnesium oxide, beryllium oxide and up to 90 mole percent zirconia. 7. The method according to claims 1 and 2, characterized by the use of a ceramic body consisting essentially of beryllium oxide, over 10 mol percent cerium oxide and zirconium oxide. B. Method according to claims 1 and 2, characterized by the use of a ceramic body consisting essentially of 5 percent by weight calcium oxide, 0.7 percent by weight silicon dioxide, 0.3 percent by weight titanium dioxide, 0.2 percent by weight iron oxide (Fe2O3), 2.0 percent by weight hafnium dioxide and 0.5 percent by weight of aluminum oxide, the remainder being zirconium oxide. Documents considered: German Patent No. 897 377; German Auslegeschrifts Ni. 1 004 989, 1001178; Hungarian Patent No. 120 862; British Patent Nos. 872,930, 802 086; French Patent No. 850 831; vakuumtechnik, 4 (8), pp. 161 to 163 (1956); Electronics; June 1949, p. 168; RCA Rev., 15 (1), pp. 46-61 (1954).