The Effect of Heat Treatment on Hydrogen Environment-Assisted Cracking of Monel K-500

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 4x10^-6 and 4x10^-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.