scope:

A fracture-mechanics approach was used in studying hydrogen- assisted crack growth in Types 308 and 347 weld-metal claddings with varying ferrite and sigma contents. A petroleum hydrodesulfurizer environment was simulated in autoclaves at 800F containing H2 at 2000 psia with admixtures of 2% H2S initially. Precracked, bolt-loaded specimens were exposed for one or more periods of 150 hr each. The H2S was unnecessary for crack growth. KIscc for Type 347 weld metal containing about 4 and 6% sigma phase was 31 ksi in1/2, as determined at crack arrest. The crack growth occurred during cooling from the exposure temperature and was due to "internal" rather than "environmental" hydrogen embrittlement. The Type 308 weld metal with similar sigma content was far more resistant to crack growth than was the Type 347.