X-ray phase analysis of martensitic transformations in austenitic stainless steels electrochemically charged with hydrogen

Hydrogen concentration gradients, formed during electrochemical charging, inducing martensitic phase transformation in austenitic stainless steels, have been extensively studied with respect to the relative stability of the austenitic phase. Phase quantitative X-ray surface analysis of distributions of martensitic phases in a thin layer, comparable to the penetration depth of X-rays, based on diffraction data taken for various diffraction reflections (2θ, Braggʹs angles) and with various radiations (λ-wavelengths), was applied for various degree of stability of the AISI type 321, 347, 304, 316 and 310 austenitic stainless steels in the surface layers, after hydrogen charging and during aging at room temperature. An examination of the relationships between γ-phase transitions in a number of stainless steels and their γ stability, revealed that the stability of the γ-phase increased (S stability factor changed from 26.5 in AISI 321 to 44 in AISI 310) the amount of α′- (from 0% in AISI 310 to 25% in AISI 347) and ɛ- (from 48% in AISI 310 to 77% in AISI 321) martensites formed, while the depth (from 6.2 μm in AISI 321 to 3 μm in AISI 310) of the martensitic phases decreased.