Experimental study of effects of hydrogen embrittlement and residual stress on mechanical properties of GTD450

The purpose of present paper is the experimental study of the effects of hydrogen embrittlement with residual stress on mechanical properties of GTD450 alloy. For this purpose, 0.5 M sulfuric acid solution was used to create one- and two-hour hydrogen embrittlement (two levels) and the indentation with a cylindrical surface was used to create a residual stress proportional to the force of 5 and 9 kN (two levels) in the specimens. Based on findings, changes in ductility and percentage of reduction area, compared to baseline conditions (no residual stress and hydrogen embrittlement) in the four test levels ranged from 42.69% to 74.68% and 11.78% to 39.58%, respectively. The results of statistical analysis also estimated the contribution of residual stress and hydrogen embrittlement in ductility as 1.15% and 67.05%, respectively. For the residual stress related to the 5 kN force, with increasing the hydrogen charging to two hours, the toughness value has decreased by 60.54%. It is also observed that the maximum changes made compared to the baseline conditions for yield stress are equivalent to 1.68% of the specimen with one hour hydrogen embrittlement and the residual stress generated by the 9kN force. Regarding the baseline conditions, necking is associated with 36% reduction area. However, when the specimen is charged for two hours, the failure occurs with minimal necking, low strain and a slight reduction area.