Fatigue Behavior of Laser Metal Deposited 17-4 PH Stainless Steel

Abstract

As additive manufacturing (AM) technology has evolved, its use has been extended to address more challenging service loading and environmental applications. To ensure broader acceptance of AM technology and to justify its use in routine production, there is a need to characterize the mechanical properties of AM parts. Laser metal deposition (LMD) or laser-directed energy deposition is an AM process in which focused thermal energy (laser) is used to fuse material, typically powder, as it is being deposited. LMD is used for repair, feature addition, rapid prototyping, and low-volume part fabrication and has great potential for producing components with composition gradients or hybrid structures. Specifically, the current work focuses on developing basic fatigue performance data for 17-4 PH stainless steel deposits made using the LMD process. Fatigue behavior for laser powder bed fusion (PBF) parts has been documented in some detail; however, the current understanding of fatigue behavior of LMD parts is limited. It is reasonable to assume that the fatigue behavior of LMD deposits is influenced by a variety of parameters, such as processing conditions, material defects, surface treatments, build orientation, and heat treatment. This paper researched the effect of heat treatment on fatigue performance; the remaining effects were held constant. Stress amplitude–number of cycles (S-N) curves—were generated to report fatigue strength and life of the deposits. Fracture surfaces were examined using optical and scanning electron microscopy. The fatigue and fracture behavior was significantly influenced by the selected parameters.