Effect of hydrogen embrittlement on the tensile properties of CrMoV steels by means of the small punch test

Abstract

In the present study, a new small punch test (SPT) methodology has been used to analyse the effect of hydrogen embrittlement on the tensile properties of three different grades of CrMoV steel: the base metal (CrMoV-1), weld metal (CrMoV-2) and this same weld metal subjected to an intermediate heat treatment (CrMoV-3). SPT results were compared with those obtained in standard tensile tests carried out in a hydrogen environment.The SPT was fully able to detect the deterioration induced by hydrogen in all steels. However, a higher level of embrittlement was obtained in the tensile tests. Furthermore, due to the aggressiveness of the environment meant, it was not possible to compare the results for CrMoV-2, which is highly susceptible to embrittlement due to its microstructure composed of low tempered bainite. As regards CrMoV-1 and CrMoV-3, the results obtained by means of the SPT fully agreed with those obtained in the tensile tests. It was observed that the poor behaviour of CrMoV-2 in a hydrogen environment was improved by applying a heat treatment of 680°C for 4h (CrMoV-3), although the excellent performance of CrMoV-1 when in contact with hydrogen was not achieved. The feasibility of the small punch test to estimate the deterioration of the tensile mechanical properties of CrMoV steels due to hydrogen embrittlement has been demonstrated.