Effect of electrolytic hydrogenation on mechanical and acoustic properties of stainless steel

The work studies the effect of hydrogen embrittlement on AISI 420 martensitic stainless steel using the acoustic method. We evaluate an estimate of changes in mechanical characteristics and informative parameters of acoustic testing by loading the samples pre-saturated with hydrogen using the electrolytic method. It was found that the parameters of Rayleigh waves depend on the degree of hydrogen embrittlement both in the unloaded and loaded states, starting from the yield point and up to the fracture. It was shown that the dependences of the propagation velocity of Rayleigh waves can be used in problems of an early assessment of hydrogen embrittlement in a material. The results of studying the influence of hydrogen concentration on the Rayleigh wave parameters serve as the basis for constructing a comprehensive acoustic method to determine the physical and mechanical characteristics of structural materials. These data make it possible to estimate the critical concentration of hydrogen, at which 80 % of the initial mechanical properties is preserved. In addition, they allow forming a criterion for the limit state of stainless steel under static loading using parameters of acoustic waves. The Rayleigh wave propagation velocities were calculated for materials in the limit state. Dependences of coefficients of the strength degradation and hydrogen embrittlement on the acoustic properties degradation coefficient were found. These relationships can be approximated by a sigmoid Boltzmann function with high correlation coefficients.