Comparison of tensile test results in high pressure gaseous hydrogen using conventional and tubular specimems

Hydrogen environment embrittlement (HEE) of X60M pipeline steel was assessed by tensile testing with tubular specimen containing high pressure hydrogen in the axial hole. Residual oxygen content as well as strain rate were varied in order to define appropriate test parameters. Maximum HEE effects were found for oxygen contents below 2 vppm and strain rates below 5*10-4 s-1, which is in the same range compared to tensile testing in an autoclave using conventional specimens. Results at such tests parameters revealed that the tensile reduction of area in hydrogen is about 10% higher compared to a similar steel tested in an autoclave at identical test conditions using conventional specimens. Further investigations are required to verify, if this difference is caused by the specimen geometry.