An investigation into the aging behavior of CoCrMo alloys fabricated by selective laser melting

This work aimed to investigate the martensitic transformation and precipitation of CoCrMo alloys fabricated by selective laser melting (SLM) under aging heat treatment. SLM-fabricated CoCrMo alloy was a mixture of gamma-phase and epsilon-phase, and the content of gamma-phase was about 70%. The content of epsilon-phase increased with the aging time. A nearly pure epsilon-phase was achieved by aging at 900 degrees C for 10 h in the SLM-fabricated part. After aging treatment for a short-time, the microhardness of the parts decreased comparing to the AS-SLM probably due to the disappearance of the honeycomb precipitates. The EDS results showed that those granular precipitates in SLM900 and SLM750 are M23C6. The content of M23C6 increased with aging time. The M23C6 precipitates and martensitic transformation enhanced the microhardness. Specimens with highest microhardness were obtained by aging at 900 degrees C for 10 h. This result established the relationship between the heat treatment process, microstructure and microhardness. (C) 2018 Elsevier B.V. All rights reserved.