Estudio de la fragilización de un acero 42CrMo4 mediante ensayos SPT en ambiente de hidrógeno

Resumo

In this work, the effect of a hydrogen-rich environment and the use of the Small Punch Test (SPT) on the behaviour of 42CrMo4 structural steel has been studied. During the course of the test, a constant source of hydrogen was introduced (in-situ test) by electrochemical methods. The hydrogen-microstructure interaction was studied by means of permeation tests, which were carried out with the same electrolyte used in the SPT tests (1 M H2SO4 + 0.25 g/l As2O3). Two different current densities (0.50 and 1.00 mA/cm2 ) were also applied. In addition, it was analysed if the use of a hydrogen precharge time before the mechanical test and the test rate used influenced the mechanical behaviour of the steel. The results obtained were analysed using different criteria: such as the reduction in energy needed to reach the maximum load using the Hydrogen Embrittlement Index (HEI) or geometric criteria through the relative reduction in the thickness of the specimen (RRT). These results show that, under the same test conditions, the use of a higher current density produces a higher embrittlement due to the higher concentration of hydrogen in the sample. The HEI also increases as the test rate decreases. However, the use of a pre-charged time does not produce significant changes in the final results.