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Molybdenum and Molybdenum Alloy Vacuum Sintering Process

Molybdenum and molybdenum alloy metal blanks are usually prepared by powder metallurgy process. After molybdenum and its alloy powders are formed by pressure, they must be sintered at high temperature and vacuum to have metallization characteristics such as low impurities, high density and high strength. The densification process of molybdenum metal is irreversible, so sintering technology is the last and most critical link in the preparation of molybdenum and molybdenum alloy metal materials by powder metallurgy.

1 Vacuum sintering mechanism of molybdenum and molybdenum alloys

Pure molybdenum sintering belongs to solid phase sintering of unit system, while vacuum sintering of molybdenum alloy is related to its alloying elements. Most micro-doped molybdenum alloys (Mo-La, Mo-Y, Mo-Ce), rare earth molybdenum alloys doped with two or even three elements, TZM, MHC doped with Ti, Zr, Hf, and C elements , TZC series alloys, AKS alloys doped with Si, Al, K, and alloys doped with a large amount of high melting point metal elements (Re, W, Ta, Nb, Ti, Cr, Si, etc.) belong to multi-system solid phase sintering (this paper The alloy impurity content is the mass fraction). The vacuum sintering process of Mo-Na(K) composites prepared by adding molybdates and a few molybdenum alloys (Mo-Cu, Mo-Ni alloys) containing low melting point metals (which are quite different from the melting point of molybdenum) belong to the multi-phase liquid phase sintering.

2 Molybdenum and molybdenum alloy vacuum sintering equipment

Molybdenum sintering process factors include heating method, temperature control, atmosphere control and so on. Different molybdenum and molybdenum alloys have different sintering process and equipment selection due to different physical and chemical indicators of raw materials and doping elements, as well as different performance requirements of sintered blanks. Vertical fusion sintering is no longer used due to limited product specifications and production volumes. Sintering of tungsten and molybdenum products must be carried out in hydrogen (H), vacuum or inert atmosphere to avoid serious oxidation and burning loss. Common heating methods include intermediate frequency induction heating and resistance heating; therefore, sintering equipment is mainly divided into intermediate frequency induction heating Or resistance heating H2 atmosphere sintering furnace, medium frequency induction heating or resistance heating vacuum sintering furnace and multi-functional sintering furnace that can be replaced by vacuum and H2 atmosphere, vacuum or H2 atmosphere and inert atmosphere (such as Ar/N2).

3 Molybdenum and molybdenum alloy vacuum sintering process

The sintering process of molybdenum and molybdenum alloys has always been a research hotspot, and its means and goals focus on obtaining small average grain size and high relative density by adjusting the heating rate, holding step, holding time, maximum sintering temperature, cooling system and sintering atmosphere. Or molybdenum metal materials with low porosity and key chemical elements such as C and O that meet the standards.

In general, the development direction of molybdenum and molybdenum alloy sintering technology is to obtain fully dense, fine-grained and homogenized sintered bodies. The sintering theory of molybdenum metal belongs to the traditional powder metallurgy sintering theory system. The sintering equipment and tooling are more closely combined with the new technology development of powder metallurgy, so the process research and control methods are more abundant and diverse, and there is a trend of more cross research. From the perspective of product requirements and the direction of equipment development, technologies such as sintering densification, microstructure homogenization, fine-graining and complex sintered special-shaped blanks during sintering of large-scale molybdenum and molybdenum alloy blanks will become the most important technologies in the sintering process of molybdenum and molybdenum alloy blanks. And the research hotspots and difficulties of molybdenum alloy sintering technology.

Selection of sintering equipment: vacuum resistance sintering furnace is a furnace for protective sintering of heated objects in a vacuum environment or inert gas, suitable for cemented carbide, ceramic materials, carbon fiber graphitization, carbon-carbon composite materials, silicon carbide products, photoelectric Vacuum or atmosphere high temperature sintering of coating materials, refractory metals (tungsten, molybdenum, tungsten-copper alloys) and other alloy materials.

The RVH series vacuum resistance sintering furnace produced by SIMUWU is a high-quality product for the vacuum heat treatment of tooling and molds. The good vacuum system and temperature control system ensure the effective progress of the vacuum sintering process.