Previous corrosion fatigue investigations of a high alloyed solution annealed
superaustenitic CrNiMoN stainless steel have shown that the fatigue strength in 62% CaCl2
solution at 120°C compared to glycerin at the same temperature is slightly decreased.
In this paper, a 27% cold deformed steel with the same chemical composition has been
investigated and results are compared to the solution annealed condition. Stress versus
number of cycles curves were recorded in glycerine, as a reference medium, and in 62% CaCl2
solution, both at a temperature of 120°C. The stress ratio (R) was 0.05 to avoid destruction of
the fracture surfaces. The testing frequency was 20 Hz.
The fracture surfaces of representative specimens which failed at high and low stress
levels were investigated by scanning electron microscopy and evaluated as function of the
medium, applied stress and different cold deformation degrees of the stainless steel. The effect
of cold deformation from the CrNiMoN stainless steel on crack initiation and propagation is
discussed. In addition, constant load tests, exposure tests and electrochemical tests were
performed.
Keywords: corrosion fatigue, stainless steel, high nitrogen steel, austenite, fracture surface