Fatigue response of additively manufactured as‐built 15‐5 PH stainless steel and effects of machining and thermal and surface treatments

Abstract

Additively produced 15-5 PH stainless steel has wide industrial applications, but the combined effects of heat treatment, machining, and shot-peening and their order have not been deeply investigated. This topic is addressed here by a 2-by-3 experimental plan that has involved S-N curve and fatigue limit determination, using vertically built cylindrical samples, tested under rotating bending. The obtained responses have been analyzed by an ANOVA-based statistical approach for comparison of fatigue trends. Results indicate that heat treatment without machining may be even detrimental for fatigue due to embrittlement. Conversely, machining with subsequent shot-peening, even without heat treatment, has a remarkable impact and leads to a doubled fatigue strength with respect to as-built material. This strength is also quite close to that achievable for wrought material. The study has been completed by micrography and fractography, to reveal the dependence of microstructure, crack initiation sites, and failure mode on the performed treatments.

An overview of factors affecting high‐cycle fatigue of additive manufacturing metals

“…In the literature, there are also studies in which different processes applied after AM are applied together 175 . Croccolo et al 176 investigated the combined effects of heat treatment, machining, and SP on 15‐5 PH stainless steel produced by AM. In the study, it was stated that the heat treatment applied without machining may be harmful for fatigue due to embrittlement 176 .…”

“…Croccolo et al 176 investigated the combined effects of heat treatment, machining, and SP on 15‐5 PH stainless steel produced by AM. In the study, it was stated that the heat treatment applied without machining may be harmful for fatigue due to embrittlement 176 . In addition, it has been stated that the SP process applied without heat treatment has a significant effect on the fatigue strength (doubled the fatigue strength of the as‐built material) 176 …”

“…In the study, it was stated that the heat treatment applied without machining may be harmful for fatigue due to embrittlement. 176 In addition, it has been stated that the SP process applied without heat treatment has a significant effect on the fatigue strength (doubled the fatigue strength of the as-built material). 176 LP is the process of applying plastic pressure (plastic compression) perpendicular to the surface of the material.…”

“…176 In addition, it has been stated that the SP process applied without heat treatment has a significant effect on the fatigue strength (doubled the fatigue strength of the as-built material). 176 LP is the process of applying plastic pressure (plastic compression) perpendicular to the surface of the material. 177 LP leads to the accumulation of compressive stresses at the surface and in the subsurface area (See Figure 13).…”

The effect of shot peening on the contact fatigue performance of C40 steel gears after laser surface melting

“…Maleki et al [25] utilized SP as a post-treatment method in a combined process to mitigate the negative effects of defects on the fatigue performance of AlSi10Mg samples. Croccolo et al [26] implemented SP as a post-processing method, demonstrating its capacity to boost the fatigue strength of 15-5 PH stainless steel, approaching levels achieved by forging processes. Moreover, Leguinagoicoa Nelson et al [27] employed SP as a post-treatment method to improve the fatigue resistance of quenched and tempered DIN 34CrNiMo6 steel.…”