Influence of ball-to-powder ratio on the preparation,microstructure and properties of S290 powder high speed steel
S290 high speed steel powder was prepared by mixing and compacting powders of WC,Mo2C,Cr3C2,VC,Co,and Fe and then vacuum sintering at 1 170-1 230 ℃. The effect of different ball-to-powder ratios on the preparation,organization and performance of S290 powder high speed steel was studied. The results show that after ball milling,the mixed powder become thin and flaky. As the ball-to-powder ratio increases,the powder become more cohesive and is subsequently broken again. At 1 200 ℃,powder with different ball-to-powder ra-tios can form dense high speed steel. With higher ball-to-powder ratio,the sintering temperature window is wider,but the shrinkage before and after sintering are more significant. The ball-to-powder ratio can also affect the size and distribution of carbides in the sintered of high speed steel microstructure. Uniform dispersion of carbides can effectively improve the hardness and performance stability after sintering and heat treatment. After sintered at 1 200 ℃,the powder high speed steel with a ball-to-powder ratio of 4∶1 shows the best hardness performance after sintering and heat treatment,with hardness values of 44HRC and 66.13HRC,respectively.
ball-to-powder ratioball-millingpowder high speed steelsinteringheat treatment
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