Process And Organization Evolution Of Co-Cr Alloy Prepared By Powder Metallurgy

Cobalt-chromium alloy is widely used in the field of high temperature wear-resistant materials and biomaterials because of its excellent high temperature properties and good biocompatibility.It can also adapt to a wider range of fields by adjusting the composition of alloys.At present,there are more researches on the preparation of cobalt-chromium alloy at home and abroad,but the preparation of cobalt-chromium alloy by powder metallurgy is still less.Powder metallurgy has its superior preparation characteristics.Powder metallurgy is an efficient,energy-saving and suitable for large-scale industrial production of metal forming process,in the preparation process can effectively alleviate loose pore,inclusion and segregation and other defects,and so on.Eliminate coarse and uneven as-cast structure.In this paper,Co-Cr-Ni alloys with two components were prepared by powder metallurgy.The effects of mixing process,sintering process and nickel content on sintering properties,microstructure evolution and strong plastic properties of the alloys were studied,and the process of mixing,sintering process and the influence of nickel content on the sintering properties,microstructure evolution and strong plastic properties of the alloys were studied.The relationship between structure and performance.The findings of the study are as follows:(1)At the beginning of mixing,the particle size of mixed powder decreases with the prolongation of milling time,and the particle size of mixed powder does not change with milling time after 60 h.The sem morphology of the mixture shows obvious flattening characteristics.The change of nickel content has no effect on the particle size and morphology of the mixed powder,but the work hardening degree of the mixed powder with high nickel content is obviously increased.(2)Co-Cr alloy sintered with low nickel content is single-phase hcp with coarse grains and dense pores.With the change of milling time,the grain size and porosity decrease.The phase composition is not affected by ball milling time.The hardness of SPS sintering is increased by 90 HV compared with vacuum sintering,but the tensile properties are obviously decreased.The grain size of low nickel sample is large and irregular,and that of high nickel sample is fine and uniform,which also shows that nickel element has the effect of grain refinement.(3)Co-Cr alloy with high nickel content has two-phase hcp and fcc structure,lower grain size,10 times difference of grain size and smaller pore size,twin and staggered substructure in the microstructure than that of Ni-Cr alloy,and the microstructure of Co-Cr alloy with high nickel content is characterized by double-phase microstructure and fcc structure,and the grain size difference between the two alloys is about 10 times.With the prolongation of milling time,the grain size is refined,and the volume fraction of fcc phase in the alloy increases slightly with the prolongation of milling time.(4)With the increase of sintering temperature,the microstructure of the alloy coarsened and the comprehensive properties decreased,especially when the sintering temperature reached 1350?,the microstructure grew up abnormally,and the sintering temperature should not exceed 1320?.(5)The mechanical properties of the sintered body are related to the original composition(nickel content)of the alloy.Compared with the low nickel alloy,the high nickel content shows higher tensile strength and plasticity,but the yield strength and hardness of the sintered alloy are lower than that of the low nickel alloy.With the prolongation of milling time,the plasticity of high nickel alloy decreases and the plasticity of high nickel alloy increases.(6)Both alloys show uniform plastic elongation and obvious orange peel structure in the tensile process.Strain-induced transformation occurs in high nickel alloy during tensile process,which is also the reason that high nickel alloy has high plasticity.