The Effects of Morphology of Ferrite and Non-Metallic Inclusions on Corrosion Behavior of As-Cast 304 Stainless Steel

The effects of morphology of ferrite and nonmetallic inclusions on corrosion resistance of as-cast 304 stainless steel (304 SS) were investigated. With the decrease in quenching temperature from 1,723 K to 1,648 K, the different microstructures of the as-cast 304 SS were obtained as the following series: austenitic-lathy δ ferrite, austenitic-colony δ ferrite, and austenitic-blocky δ ferrite and the average inclusion size increased. The electrochemical results show that the sample with the microstructure of austenitic-lathy δ ferrite and smaller size inclusions had a higher corrosion tendency and the lower pitting resistance. Furthermore, the effect of morphology and content of ferrite on corrosion resistance was greater than that of inclusion size under the current experimental conditions. Therefore, a promising method was developed to improve the corrosion resistance of as-cast 304 SS by changing the solidification process.