Effect of tin addition on the microstructure development and corrosion resistance of sintered 304L stainless steels

The effect of tin powder addition on the microstructure development during sintering and corrosion resistance of the 304L-Sn metallurgical system was investigated, Specimens containing 1 to 4 wt% Sn were sintered in hydrogen at temperatures ranging from 800 to 1300 degrees C, During sintering at temperatures below 1000 degrees C,most of the liquid phase was retained at the site originally occupied by the tin powder. At temperatures above 1050 degrees C, the tin-base liquid phase spread and uniformly distributed among the 304L solid particles. Adding tin powder and the resultant liquid phase led 304L powder compacts to expand during sintering. An immersion test in 1M H2SO4 and metallographic observation showed that pitting always initiated at the spots with lower tin content, and the tin atom enrichment had the beneficial effect of improving the corrosion resistance of sintered 304L stainless steels.