How to Strengthen Cermets with Tungsten Carbide Molybdenum Tantalum Solid Solution Composite Powder

TiC cermets consisting of hard phase and bonding phase are the best choice of indexable tool materials for modern high-efficiency and high-speed cutting because of their higher hardness and wear resistance, sufficient strength and toughness, high heat resistance and good chemical stability. However, its fatal weakness is brittleness and toughness is insufficient, and the matching wetting problem between hard phase and bonding phase has not yet been solved.

The method of adding metal carbides determines the distribution of metal elements. In order to strengthen the properties of cermet materials, a kind of micro-nano tungsten carbide/molybdenum/tantalum solid solution composite powder was prepared, which was used to strengthen titanium cermet. The process is as follows:

(1)Ingredients: 850g tungsten powder, 420g molybdenum powder, 420g tantalum powder and 150g graphite powder were weighed and 75g cerium oxide powder was added; the purity of tungsten powder, molybdenum powder, tantalum powder and graphite powder was > 99.9%, the average particle size was 20-100 micron; the average particle size of cerium oxide powder was less than 20 micron;

(2)Solid-state reaction of high-energy ball milling: the raw materials and tungsten carbide balls were loaded into stainless steel vacuum ball mill tank for high-energy ball milling. The ball-to-material ratio was 10:1, the ball milling speed was 300 revolutions/min, and the milling time was 36 hours. The mixed powder of (Mo, Ta) C solid solution powder and W+C+ (W, Mo, Ta) C was obtained.

(3)Thermo-chemical reaction: The reaction products obtained from step (2) were put into a high temperature atmosphere furnace, and then thermo-chemical reaction was carried out at 800 C for 60 minutes to obtain tungsten-molybdenum-tantalum carbide solid-solution composite powder with an average particle size of about 100 nm and uniform distribution; after the reaction was completed, the hydrogen gas was closed and the obtained tungsten-molybdenum-tantalum carbide solid-solution composite powder was cooled under the protection of nitrogen gas. But after room temperature, it is packed in vacuum under the protection of nitrogen.

The prepared tungsten carbide/molybdenum/tantalum solid solution composite powder is micro-nanometer and uniformly distributed. The results show that the addition of tungsten carbide, molybdenum and tantalum solid solution composite powder into cermet powder can not only enhance the dispersion, wetting and grain refinement of the above-mentioned metal carbides, but also evenly diffuse Mo, W and Ta to TiC particles at sintering temperature, and replace Ti in TiC lattice, reduce the contact between TiC particles, prevent their aggregation and growth, and make TiC-based particles grow up uniformly. The grain size of cermet is finer and the structure is more uniform, which has a significant effect on improving the overall performance of cermet.

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