The influence of applied stress rate on the stress corrosion cracking of 4340 and 3.5NiCrMoV steels in distilled water at 30 °C

Linearly Increasing Stress Tests conducted in 30 °C aerated distilled water using as-quenched 4340 and 3.5NiCrMoV turbine rotor steels indicated that stress corrosion cracking occurred at all applied stress rates for 4340 steel, whilst only at applied stress rates less than or equal to 0.002 MPa s−1 for the turbine rotor steel. The crack velocity increased with increasing applied stress rate for both steels with the maximum crack velocity for 4340 steel corresponded to vII in fracture mechanics tests in room temperature water. The fracture surface morphology was mixed mode consisting of intergranular and transgranular fracture regions.