Study of the impact of phase composition on the mechanical properties and corrosion behavior of 304 stainlesssteel

This study systematically investigated the microstructure, mechanical properties, and corrosion resistance of a low-impurity and low-ferrite 304 stainless steel (LSS) prepared through a high purity smelting technology (HPST), and compared them with those of conventional 304 SS (CSS). Microstructural characterization revealed that no martensitic transformation or σ phase occurred in the LSS, and its impurity and/or inclusion content were extremely low, achieving a higher degree of material purification than the CSS. Both materials exhibit the highest hardness in the rolling direction (RD), but demonstrate slightly lower resistance to elastic deformation and corrosion resistance in this direction. The impedance values shown in the LEIS test depicts a decreasing order of transverse direction (TD) > normal direction (ND) > RD. This is primarily attributed to the differences in ferrite content in different directions of the material caused by rolling, namely RD > ND > TD, as well as the contents of σ phase and martensite. The optimized ferrite content, absence of martensitic phase and low-impurity content of the LSS endowed it with superior mechanical properties and corrosion resistance compared to that of the CSS material. Thus, this study shows that the HPST technique is a good method of developing austenitic stainless steels with optimal performance properties for the target environment of this study.