HYDROGEN TRAPPING BEHAVIOR IN PLAIN CARBON AND CR-MO ALLOY STEEL

ABSTRACT Observations on hydrogen trapping behavior in terms of high resolution autoradiography and isothermal analysis of hydrogen degasing, by varying austenitizing temperature, in cathodically charged plain carbon steels and Cr-Mo alloy steels have been carried out. From autoradiographs, trapped hydrogen quantity at observed sites such as martensite laths, prior austenite grain boundaries, spherical precipitates and non-metallic inclusions, has been estimated. By comparison of these values with the results of isothermal degasing analysis, trap sites were classified in three categories depending on the energy of interaction between hydrogen. Concerning the characteristics of trap sites, specially for martensite laths interfaces and prior austenite boundaries, segregation of impurities and existence of retained austenite or fine precipitates at the interfaces must be noted.