Effect Of The Raw Powder Size Of Hard Phases On The Microstructure And Properties Of Cermets

Fine grains in material can improve hardness , strength and toughness. Hardmetals and cermets both belong to particle strengthened composite. To change the particle size of hard phase can greatly affect their properties. Based on practical applications and future development, this paper used coarse and fine starting powders and adopted vacuum sintering technique to prepare two groups of hardmetal and cermet specimens which had the same raw material compositions and different grain size.After the high compact specimens were produced, the mechanical properties such as hardness, strength and fracture toughness were measured based on the uniform standard. Then the microstructure was analyzed mainly using XRJD, SEM and EDS.Through comparing the effect of different starting powder particle size on the microstructure and analyzing the relationship of microstructure and macroscopical mechanical properties , some conclusions can be made. Hardmetals made from micron grained WC had a good improvement on hardness and strength and their microstructure didn't have some cavities as in hardmetals made from coarse WC. The rims in structure of cermets made from micron grained TiC had two layers that were inner rim and outer rim, while these can be found in cermets made from submicron grained TiC. What is more, it can be found a new phase in cermets made from submicron grained TiC. The hardness of submicron grained cermet was improved largely and the strengthness was enhanced a little, but the toughness reduced.