Hydrogen embrittlement susceptibility of laser-hardened 4140 steel

Slow strain rate tensile (SSRT) tests were performed to investigate the sus ceptibility to hydrogen embrittlement of laser-hardened AISI 4140 specimens in air, gaseous hydrogen and saturated H2S solution. Experimental results indicated that round bar specimens with two parallel hardened bands on oppo site sides along the loading axis (i.e. the PH specimens), exhibited a huge reduction in tensile ductility for all test environments. While circular-h ardened (CH) specimens with I mm hardened depth and 6 mm wide within the ga uge length were resistant to gaseous hydrogen embrittlement. However, fully hardened CH specimens became susceptible to hydrogen embrittlement for tes ting in air at a lower strain rate. The strength of CH specimens increased with decreasing the depth of hardened zones in a saturated H2S solution. Th e premature failure of hardened zones in a susceptible environment caused t he formation of brittle intergranular fracture and the decrease in tensile ductility. (C) 2000 Elsevier Science S.A. All rights reserved.