Fatigue response of additively manufactured Maraging Stainless Steel CX and effects of heat treatment and surface finishing

Abstract

This paper deals with the novel topic of the fatigue response of additively manufactured Maraging Stainless Steel CX. A two-by-two factorial plan was arranged, to experimentally assess the effects of heat treatment and machining on the fatigue strength in both finite and infinite life domains. The two factors were regarded as on–off, taking the untreated unmachined condition as a reference for comparisons. Cylindrical specimens with vertical build orientation were involved in the fatigue campaign under four-point rotating bending. The results indicate that the fatigue strength may be remarkably incremented (up to five times) with respect to the as received conditions, especially thanks to surface smoothing and taking advantage of a very low porosity level. Heat treatment strengthening mechanisms were also interpreted in the light of optical and electron microscope observations. Fatigue enhancement arises from precipitate size increment throughout the conducted heat treatment, although the fracture mode turns to be more brittle.