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 degrees C-1 h, and another was subjected to 1200 degrees C-1 h and then 850 degrees 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-epsilon phase is increased by heat treatments. The results showed that the hardness increases from 376 to 437 HV owing to increased epsilon 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 degrees C-5 h, due to the higher volume fraction of epsilon phase and carbides. Finally, the wear mechanisms of the as-built and heat-treated samples were compared and discussed in this work.