Effect of heat treatment on the microstructure and fatigue strength of CoCrMo alloys fabricated by selective laser melting

[Display omitted] •CoCrMo alloy samples fabricated by selective laser melting (SLM) were heat-treated.•Heat treatment resulted in drastic fatigue strength improvement.•Elimination of molten pool boundaries led to enhanced fatigue strength.•Fatigue strength was affected by the high number of layers and long processing time. We investigate the effect of heat treatment on the microstructure and fatigue strength of CoCrMo alloys fabricated by selective laser melting. Specimens are prepared in vertical and horizontal orientations with respect to the build direction and are subjected to heat treatment at 1150 °C for 1 h. Evaluation of the microstructure and fatigue strength reveals that the heat-treated specimens have significantly higher fatigue strength than the as-built specimens, which is attributed to the occurrence of recrystallization and the disappearance of molten pool boundaries during heat treatment. However, despite microstructure homogenization in the heat-treated samples, they exhibit mechanical anisotropy (similar to the as-built samples), which is attributed to the influence of the sample orientation on the number of layers and the processing time.