Stress corrosion cracking of rotor steels in carbonate/bicarbonate and sodium hydroxide solutions

In this study, the stress corrosion behavior of 3.5%NiCrMoV and 1%CrMoV steels was investigated. Tests were conducted at 95°C in carbonate/bicarbonate and sodium hydroxide solutions. Results from slow strain rate tensile tests and fracture mechanics experiments were compared. A new, easily machinable, specimen geometry for fracture mechanics experiments was tested. The influence of pH, potential, microstructure and inclusions were studied. Stress corrosion cracking (SCC) was found with all three steels in the 3.5M NaOH solution at active, passive and transpassive potentials. In the 1M carbonate/ bicarbonate solutions, the 1%CrMoV steels showed very severe cracking only during slow strain rate experiments. No major difference in cracking behavior was found between a regular 3.5%NiCrMoV steel and a super clean 3.5%NiCrMoV steel with low Mn and Si content. In acidic CO₂/H₂O environments, crack tip blunting was observed due to strong dissolution processes.Applied Science, Faculty ofMaterials Engineering, Department ofGraduat