The influence of heat treatment on hydrogen environment-assisted cracking of Monel K-500 was evaluated through slow-rising stress intensity loading of two aging conditions while immersed in NaCl solution under cathodic polarizations. Results indicate that both the non-aged and over-aged conditions were immune to HEAC at potentials more positive than -1000 mV_(SCE), while both were susceptible at -1200 mV_(SCE). Crack growth kinetics and fractography confirm the enhanced susceptibility of the over-aged material at -1200 mV_(SCE); K_(TH) of 16 and 17 MPa√m and da/dt_(II) of 4×10~(-6) and 4×10~(-5) mm/s were observed for the non-aged and over-aged conditions, respectively. These differences are discussed in the context of possible changes in microstructure, with particular emphasis on sulfur segregation to grain boundaries and global slip morphology.
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