Effect of Heat Treatment on Hardness of Co-Cr-Mo Alloy Deposited With Laser Engineered Net Shaping

AbstractThe hardness of the samples fabricated with Co-Cr-Mo alloy powder using Laser Engineered Net Shaping process was tested. Three different process parameters (laser power, feed rate and scan speed) at two levels were used to fabricate the samples for L4 orthogonal array of Taguchi method. The hardness obtained was 446Hv with high laser power, low feed rate and high scan speed. With these process parameters, another set of nine samples were fabricated to apply heat treatment. Three heat treatment parameters (Solutionizing time, ageing temperature and ageing time) at three levels were used for L9 orthogonal array. The solutionizing timings were 30, 45 and 60minutes at 1200oC. One set from these nine samples was with no ageing and the other two sets were aged at 815 and 830oC for 2, 4 and 6hours. The test results of hardness have revealed that the samples aged with 830oC for two hours have shown highest hardness (much more than the wrought material) but with much variance on the same surface. It has also been established by ANOVA that the solution time and ageing temperature have only a little effect on the hardness but the ageing time has considerable effect and prolonged ageing will result in loss of hardness