Chemical Homogeneity as a Key Factor in the Martensitic Transformation of Powder-Metallurgically Processed X2CrNi18-9 Steel: Implications for Hydrogen Embrittlement

Abstract Austenitic stainless steels produced by powder metallurgy (PM) reportedly exhibit higher resistance to hydrogen embrittlement than conventionally produced grades. This improved resistance is commonly attributed to their lower tendency for martensitic phase transformation. One previously unaddressed factor that may contribute to this behavior is the difference in chemical homogeneity between PM and conventionally manufactured parts. The present work investigates chemical homogeneity as a factor influencing the phase stability of PM-produced metastable austenitic steel X2CrNi18-9. Slow strain rate tensile tests were conducted at − 50 °C on cast and hot-formed (wrought) specimens, as well as on PM conditions produced by hot isostatic pressing and PBF-LB/M. Simultaneous electron backscatter diffraction and energy-dispersive X-ray spectrometry of the wrought material reveal band-like Ni and Cr segregations elongated along the deformation direction. Ni-depleted regions were identified as preferential sites for martensite formation, which propagates in a block-like manner into regions of higher austenite stability. In contrast, the PM conditions exhibit higher chemical homogeneity, resulting in an overall lower fraction of deformation-induced martensite. This study demonstrates that chemical homogeneity is a critical parameter in the assessment of hydrogen embrittlement resistance of austenitic stainless steels and should be considered alongside other influencing factors.