The influence of heat treatment on the microstructure, hardness, and wear properties of CoCrMo alloy produced by powder bed fusion of metals using a laser beam (PBF-LB/M) process

ASTM F75, a CoCrMo alloy manufactured using the powder bed fusion of metals using a laser beam (PBF-LB/M) process, has been processed to the solution and aging heat treatments, for investigating their effects on the microstructural developments, hardness, and wear properties. One group of samples was heated at 1200 °C—1 h, and another was subjected to 1200 °C—1 h and then 850 °C—5 h. After evaluating the results of the optical microscopy, field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy, X-ray diffraction, microhardness, and pin-on-disk wear tests, it was found that a fine cellular microstructure inside long columnar grains of as-built samples has been replaced with a honey-comb like structure and coarse grains with some precipitates after solution and aging treatments, respectively. Also, the amount of HCP-ε phase is increased by heat treatments. The results showed that the hardness increases from 376 to 437 HV owing to increased ε phase and precipitates. Meanwhile, wear tests indicated that the wear resistance of additively manufactured samples increased with heat treatments, especially after aging at the condition of 850 °C—5 h, due to the higher volume fraction of ε phase and carbides. Finally, the wear mechanisms of the as-built and heat-treated samples were compared and discussed in this work.