HYDROGEN EMBRITTLEMENT OF STAINLESS-STEELS BY LITHIUM HYDRIDE

Reference is made to possible use of LiH and other hydrides as reactor shielding materials. Tensile tests were made on 304L and 17-7 PH stainless steels in contact with LiH powder. Reduction in area relative to ductility in air decreased for both alloys. It was essential that the LiH was baked in contact with the alloys for the ductility loss to be observed; thermodynamic and kinetic evidence indicated that the LiH was reacting with surface oxides to furnish left bracket H right bracket to the steel. The depth to which hydrogen affected fracture surface morphology in 304L was greater than could be accounted for by diffusion, and it was concluded that dislocation transport accounted for the difference. Although direct evidence was not available, the locale of hydrogen damage in 304L was suggested to be the interface between the matrix and nonmetallic inclusions. A rationale based on this possibility was shown to be self-consistent. The generality of the importance of left bracket H right bracket furnished by LiH reaction was illustrated by the results on 17-7 PH.