Effect of annealing treatment on microstructure, mechanical property and anti-corrosion behavior of X2CrNi12 ferritic stainless steel

The effect of annealing temperature on the microstructure, mechanical property and anti-corrosion behavior of the X2CrNi12 ferritic stainless steel were systematically investigated. The results demonstrate that a large amount of (Fe, Cr)23C6 precipitated at the ferrite grain boundaries after annealing below 740 °C. The precipitation of the (Fe, Cr)23C6 was prevented with the increase of annealing temperature, and the martensite content gradually increased, which improved the tensile strength, yield strength, and hardness of the steels, while the elongation was decreased. The best comprehensive mechanical properties can be obtained at the annealing temperature of 850 °C and 950 °C. The ductile-dimple fracture is the primary fracture mode for the steels. The corrosion rates of the stainless steels first decreased and then increased with the increase of annealing temperature. The 770 °C-annealed steel has the best anti-corrosion ability. The corresponding corrosion mechanism can be attributed to the pitting corrosion induced by the (Fe, Cr)23C6 and martensite. Moreover, the precipitation of (Fe, Cr)23C6 could consume the Cr in the matrix and prevent the formation of passive film on the surface. And the phase transformation stress in the martensite can accelerate the local corrosion of the steel matrix.