Hydrogen Embrittlement in 17-4PH Stainless Steel

Abstract : Tensile and Charpy impact test specimens of 17-4PH stainless steel in Conditions. A, H900, H950, H1000, H1050, H1100, H1150 and H1150M were cathodically charged with hydrogen for various lengths of time. After charging, the specimens were mechanically tested at room temperature. The tensile tests were conducted at strain rates of 0.02, 0.2, 2.0, and 20 min-1. Changes in mechanical properties (reduction in area, ultimate strength, hardness) were correlated with heat treatment, hydrogen charging level, and strain rate. Scanning electron microscope (SEM) fractography was employed to characterize fracture surfaces and provide information concerning the failure modes that were operating. In the tensile investigation, hydrogen charging was shown to greatly reduce the percent reduction in area (% RA) of 17-4PH stainless steel in all heat treatment conditions. The decreases became more pronounced as the yield and ultimate strengths increased and with increased charging time. For a given charging treatment and aging condition the % RA was shown to be a function of strain rate, the largest decrease in % RA being measured at intermediate strain rates.