Embrittlement of laser surface-annealed 17-4 PH stainless steel

Stress corrosion cracking and fatigue crack growth behavior were determined in 17-4 PH stainless steel under various metallurgical conditions, includi ng the H900 (482 degreesC/1 h), H1025 (552 degreesC/4 h) aging and laser su rface annealing treatments. Peak-aged (H900) specimens locally irradiated b y laser beam consisted of a portion of composite region (CR), in which comp rised of soft laser-annealed (LA) zones on the outer surfaces and the hard base metal in between. Slow extension rate tensile tests were performed at room temperature in a saturated H,S solution to evaluate the: hydrogen embr ittlement susceptibility of various specimens. H900 specimens show an obvio us improvement in impact toughness after irradiating by laser. Regardless o f testing environments, H900 specimens exhibited better tensile properties than the other specimens. Experimental results also indicated that H900 spe cimens had the highest fatigue crack growth rates among the specimens, part icularly at low stress intensity factor range. The retardation of crack gro wth in the region ahead of the CR in the LA specimens was rather pronounced . For compact tension specimens tested in gaseous hydrogen, enhanced crack growth was correlated with quasi-cleavage fracture in contrast to transgran ular fatigue fracture in air. (C) 2001 Elsevier Science B.V. All rights res erved.