Tungsten-copper composite materials are two-phase pseudo alloys composed mainly of tungsten and copper elements. They are metal-based composite materials. Due to the large difference in the physical properties of metal copper and tungsten, they cannot be produced by melting and casting, and are generally produced by powder alloy technology.
Tungsten-copper alloys have a wide range of uses, most of which are used in aerospace, aviation, electronics, electricity, metallurgy, machinery, sports equipment and other industries. Secondly, they are also used to manufacture arc-resistant high-voltage electrical switches, contacts and rocket nozzle throat linings, tail rudders and other high-temperature components. They are also used as electrodes for electrical machining, high-temperature molds and other occasions that require electrical conductivity and thermal conductivity and high temperature use.
Process introduction
The process flow of making tungsten-copper alloys by powder metallurgy is powder making-mixing-pressing-forming-sintering dissolution-cold processing.
After pressing and forming, the mixed powder of tungsten-copper or molybdenum-copper is liquid-phase sintered at 1300-1500°. The material prepared by this method has poor uniformity, many closed voids, and the density is usually less than 98%. However, the activation sintering method, mechanical alloying method, or oxide reduction method with a small amount of nickel can improve the sintering activity, thereby improving the density of tungsten copper and molybdenum copper alloys. However, nickel activation sintering will significantly reduce the electrical and thermal conductivity of the material, and the introduction of impurities by mechanical alloying will also reduce the conductivity of the material; the oxide co-reduction method is a cumbersome process for preparing powders, with low production efficiency and difficult to mass produce.
Injection molding method
High-density tungsten alloys are made by injection molding. The manufacturing method is to mix nickel powder, copper tungsten powder or iron powder with a uniform particle size of 1-5 microns with tungsten powder and tungsten powder with a particle size of 0.5-2 microns and 5-15 microns, and then mix 25%-30% of organic binder (such as paraffin or polymethyl methacrylate) for injection molding, remove the binder by steam cleaning and irradiation, and sinter in hydrogen to obtain a high-density tungsten alloy.
Copper Oxidation Powder Method
Oxidation copper powder (mixed and ground to reduce to copper) is used instead of metal copper powder. Copper forms a continuous matrix in the sintered compact, and tungsten serves as a reinforcing framework. The high expansion component is constrained by the surrounding second component, and the powder is sintered in wet hydrogen at a lower temperature. It is introduced that the use of very fine powder can improve the sintering performance and densification to more than 99%.
Tungsten and molybdenum skeleton infiltration method
First, tungsten powder or molybdenum powder is pressed into shape and sintered into a tungsten or molybdenum skeleton with a certain porosity, and then infiltrated with copper. This method is suitable for tungsten copper and molybdenum copper products with low copper content. Compared with tungsten copper, molybdenum copper has the advantages of small mass, easy processing, linear expansion coefficient, thermal conductivity and some main mechanical properties comparable to tungsten copper.
Although the heat resistance is not as good as tungsten copper, it is better than some heat-resistant materials, so the application prospect is good. Because the wettability of molybdenum copper is worse than that of tungsten copper, especially when preparing molybdenum copper with low copper content, the density of the material after infiltration is low, resulting in the material’s air tightness, electrical conductivity, and thermal conductivity failing to meet the requirements, and its application is limited.
Tungsten copper alloy combines the advantages of copper and tungsten, with high strength, high specific gravity, high temperature resistance, arc erosion resistance, good electrical and thermal conductivity, and good processing performance. High-quality tungsten powder and oxygen-free copper powder are used, and isostatic pressing (high-temperature sintering-copper infiltration) is used to ensure product purity and accurate ratio, fine organization, and excellent performance. Good arc breaking performance, good electrical conductivity, good thermal conductivity, and small thermal expansion.