Experimental evaluation of micromechanical damage produced by hydrogen in 316L steel for the first wall of fusion reactors

This paper analyzes the process of progressive damage produced by mechanical origins (plasticity) and environmental causes (hydrogen embrittlement) in 316L austenitic stainless steel for the first wall of fusion reactors. Results of the analysis show that the micromechanical damage created by hydrogen is concentrated in an external circumferential ring with the same center as the cross sectional area of the notched samples. The microscopical appearance of this embrittled zone or damaged area is very rough and irregular at the microscale, with evidence of microcracking or secondary cracking, in contrast with the smooth surface (at the microscale) created by microvoid coalescence (dimpled fracture) in the inner core which is not embrittled by hydrogen and thus fails by mechanical reasons. The depth of the hydrogen damaged zone is quantified by fractographic methods and related to the test variables.