Abstract
Changes of fracture modes and of the critical stress intensity factor (K_<IH>) for hydrogen assisted-cracking (HAC) were studied using wedge opening-load (WOL) specimens (made of AISI 4340) as a function of tempering temperature. The test result showed that with the rise of tempering temperature, fracture modes and the K_<IH> markedly changed beyond the critical tempering temperature about 500℃.
