The influence of nitrogen content on corrosion fatigue crack growth behavior of duplex stainless steel

The effect of nitrogen content on the corrosion fatigue crack growth (FCG) behavior of 22% Cr duplex stainless steel (DSS) in chloride solution was investigated. Corrosion fatigue crack growth rate measurements employing fracture mechanics specimens were performed in chloride containing solution. The experimental results showed that the tensile strength and elongation of 22% Cr DSS increased with an increasing amount of nitrogen (range: 0.103-0.195 wt.%) in DSS. Furthermore, nitrogen also caused increases in the microhardness of both ferrite and austenite. The experimental results indicated that the FCG rates of 22% Cr DSSs in 3.5 wt.% NaCl solution at 80 °C were higher than that in air. The results revealed that nitrogen in the range of 0.103-0.195 wt.% did not significantly affect the FCG rate of 22% Cr DSS in air and in 3.5 wt.% NaCl solution at 80 °C, at 1 Hz. However, at a frequency of 0.1 Hz and in 3.5 wt.% NaCl solution at 80 °C, a higher FCG rate was found in the low-N DSS (0.103 wt.% N) compared with those with high nitrogen content (>0.153 wt.% N). As the nitrogen content increased, the content of ferrite phase, which was susceptible to hydrogen embrittlement, in DSS decreased. As a result, the corrosion fatigue crack propagation rate was reduced.