Effect of Cr-rich carbide precipitates on austenite stability and consequent corrosion behavior of ultrafine-grained 304 stainless steel produced by cryogenic rolling and annealing treatment

The effect of Cr-rich carbide precipitates on the austenite stability and corrosion behavior of ultrafine-grained 304 stainless steel obtained by cryogenic rolling and subsequent different reversion annealing temperatures were systematically studied. Experimental results demonstrated that the number and size of Cr-rich carbide precipitates gradually decreased as the annealing temperature increased from 700 °C to 900 °C. The tensile tests revealed that the martensite volume fraction rapidly increased as the true strain increased for the ultrafine-grained sample prepared by annealing at 700 °C when compared to 800 °C and 900 °C. The results of the electrochemical experiments revealed that the corrosion resistance of ultrafine-grained samples increased with annealing temperature from 700 °C to 900 °C, with annealing at 900 °C providing the best pitting corrosion resistance. According to the findings, the Cr-rich carbide precipitates formed during the reversion annealing process reduced the austenite stability and corrosion resistance of ultrafine-grained stainless steels, as evidenced by promoting strain-induced martensite formation and occurrence of pitting corrosion.