Effect of Ageing Treatment on the Stress Corrosion Cracking Susceptibility of Precipitation Hardenable 17-4 PH Stainless Steel

Precipitation hardenable 17-4 PH stainless steel was subjected to a solution-annealing heat treatment followed by ageing treatments at 580 degrees C for durations up to 6 h. Slow-strain rate testing (SSRT) has been done for the material in the solution-annealed condition, peak-aged condition and overaged condition in a chloride environment at a strain rate of 3 x 10(-7)/s. The stress corrosion cracking (SCC) susceptibility of the material in different aged conditions was evaluated by comparing the percentage reduction in ductility in the environment in the SSRT test reference to the ductility of the individual material conditions in air. Results indicated that the solution-annealed material is more resistant to stress corrosion cracking than the material in aged conditions, i.e. ageing treatment leads to a deterioration in the stress corrosion cracking resistance of the material in chloride environment with the maximum susceptibility in peak-aged condition. The SCC susceptibility of the material in chloride environment has been found to be directly related to the strength of the material.