The low cycle and high cycle fatigue behavior of additively manufactured 17-4 PH stainless steel

The monotonic and cyclic behavior of the 17-4 PH stainless steel was investigated. The mechanical behavior of conventionally manufactured (CM) specimens was compared with additively manufactured (AM) specimens fabricated using selective laser melting (SLM). Fully reversed strain-controlled fatigue experiments were conducted with strain amplitudes ranging from 0.15% to 1.00%. Under monotonic loading, both CM and AM presented similar tensile strength and yield strength. However, the AM material has lower ductility and slightly lower elasticity modulus than these of the CM counterpart. Under cyclic loading, the fatigue strength of the AM is significantly lower than that of the CM steel in both high cycle fatigue and low cycle fatigue regimes. The reduced ductility and fatigue strength of the AM steel is mainly associated with internal defects resulted from the manufacturing procedure, such as un-melted particles and entrapped voids, and poor surface finish. The AM 17-4 PH stainless steel used in this study presented higher static strength, ductility, and fatigue performance than these of the same material found in the literature. The higher mechanical performance of the former can be attributed to the combination of equiaxed uniform grains with a significant amount of the face-centered-cubic (FCC) austenite phase in the microstructure, resulted from a combination of manufacturing parameters and post-manufacturing heat treatment.