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

Abstract 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 γ-phase and e-phase, and the content of γ-phase was about 70%. The content of e-phase increased with the aging time. A nearly pure e-phase was achieved by aging at 900 °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 M 23 C 6 . The content of M 23 C 6 increased with aging time. The M 23 C 6 precipitates and martensitic transformation enhanced the microhardness. Specimens with highest microhardness were obtained by aging at 900 °C for 10 h. This result established the relationship between the heat treatment process, microstructure and microhardness.