The Effect of Applied Potential on Corrosion Fatigue Crack Growth Rates of a Ni-Cr-Mo-V Turbine Disc Steel in a Room Temperature 12M NaOH Solution

Abstract

Abstract Corrosion fatigue crack growth rates were obtained for an ASTM A 471 Ni-Cr-Mo-V turbine disc steel tested in a room temperature 12M NaOH solution. Tests were conducted under open circuit and applied potentials. The range of applied potentials was −530 to −1280 mVn, which includes the passive, active peak, open circuit, and cathodic regimes. For tests at a frequency of 1 Hz, an R ratio equal to 0.5 and a sinusoidal waveform, the maximum environmental effect was an order of magnitude increase in the fatigue crack growth rate at the lowest cathodic potential. This environmental effect decreased as the applied potentials rose. Applied potentials in the passive range eliminated any environmental acceleration of fatigue crack growth rates. The extent of intergranular fracture increased as potentials dropped in the cathodic range.