Effects of proton irradiation on nanoindentation strain-rate sensitivity and microstructural properties in L-PBF 17–4 PH stainless steels

Laser power based additive manufacturing techniques such as laser powder bed fusion (L-PBF) of 17–4 PH stainless steels have been proven to be effective manufacturing processes with acceptable quality outputs. In this work, the effects of 1 MeV proton irradiation (with a fluence of 1 × 1019 ions/cm2) on micro-mechanical properties, microstructure, and strain-rate sensitivity have been experimentally investigated in this specific alloy. Strain-rate sensitivity of as-built (unirradiated) and irradiated 17–4 PH stainless steel were studied in different strain rates of 0.01, 0.05, 0.1, 0.25, 0.5, 0.75, and 1 s−1, and for each strain rate 100 indentations were made. Micro-mechanical properties, yield and maximum shear strength of proton-irradiated L-PBF 17-4 stainless steel parts were substantially affected by means of a significant change on strain rates, concretely at strain rates higher than 0.25 s−1 when compared to as-built parts at two different volumetric energy densities. Grains were noted to become slightly finer due to radiation for irradiated parts with the same volumetric energy density, based on electron backscatter diffraction (EBSD) microstructural quantitative analysis of scanned regions. These findings are relevant due to the applications of these alloys in the fabrication of components subjected to irradiation and extreme working conditions, and are factors to consider when evaluating the use of additive manufacturing to fabricate intricate nuclear parts.