Effects of heat treatment and build orientations on the fatigue life of selective laser melted 15-5 PH stainless steel

Abstract Effects of heat treatment (aging and overaging) and build orientations on the fatigue life of Selective Laser Melted (SLM) 15-5 precipitation hardening (PH) stainless steel are reported. Low cycle fatigue (LCF) life of aged specimens is better than specimens in as-built condition for both vertical and horizontal build directions. On the contrary, high cycle fatigue (HCF) life of aged specimens is less than its as-built counterpart. Aging resulted in precipitation strengthening of the matrix through Cu-rich precipitation, but this makes specimen more defect sensitive in HCF regime. Overaging makes specimen ductile through coarsening of Cu-rich precipitates and increases the amount of retained austenite. This results overaged specimens to be less defect sensitive than aged specimens in HCF regime. Presence of irregular shaped defects e.g. voids, un-melted regions etc in SLM specimens reduces its fatigue life than its wrought counterparts. Relatively less number of defects is found for vertically built SLM specimens. However, orientations of defects being perpendicular to the loading axis, creates more stress concentration around a defect leading to lower fatigue life of the vertical SLM specimens. Present study could be used as a guideline to select proper build strategy and heat treatment for SLM 15-5 PH stainless steel for a desired fatigue life.