Environmental stress intensity for maraging steel

Stress intensity, K, values for 18 Ni 1800 MPa maraging steel stressed to 90% of its K_IC level and exposed to water, hydraulic oil (servo 317) and water inhibited with 0.5, 1.0, 1.5 and 2% dichromate (pH about 7.5) for various durations were determined using the modified wedge opening loading (WOL) technique. Experiments revealed that there is no appreciable deterioration in K in oil and water inhibited with 1.5% and 2% dichromate even after 25 days exposure. The threshold stress intensity is reached after 15 days in 0.5% dichromate inhibited water at 40 MPa m^1/2. Stress corrosion crack growth rate in water is about 40 times the rate in hydraulic oil. Crack path characteristics of the WOL-tested maraging steel specimens in different environments are briefly mentioned.