The Effect of Cold Working on the Corrosion Fatigue Behaviour of a CrNiMoN Austenitic Stainless Steel

Corrosion fatigue investigations of a solution annealed austenitic CrNiMoN27-30-3-0.3 stainless steel have shown that a minimum reduction of fatigue strength in 62% CaCl₂ solution at 120°C compared to glycerin at the same temperature is present.
            In this paper, a 14% 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 ratio between upper and lower stress level (R value) was 0.05 to avoid destruction of the fracture surfaces and the testing frequency was 20 Hertz.
            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 medium, applied stress and different cold deformation of the stainless steel. The effect of cold deformation from the CrNiMoN27-30-3-0.3 stainless steel on crack initiation and propagation is discussed. In addition, constant load tests, exposure tests and electrochemical tests were made.
Keywords: corrosion fatigue, stainless steel, high nitrogen steel, austenite, fracture surface