Silicide Phase Formation and Its Influence on Liquid Phase Sintering in 316L Stainless Steel with Elemental Silicon Additions

Abstract

Elemental additions of silicon to sintered 316L stainless steels were found to cause the formation of liquid phases at three temperatures. The first two of these, at 1060 and 1155°C, were owing to heat generated by an exothermic reaction between the steel and its silicon addition leading to the formation of a complex mixture of silicide phases involving iron, chromium, and nickel. Alloying between the silicon and 316L stainless steel then lowered the solidus temperature of the steel and a further liquid phase was formed when sintering temperatures exceeded the new solidus of 1190°C. Full sintered densities were not achieved despite the presence of liquid phase and the use of relatively high sintering temperatures. This was because of the large pores that remained at the sites where the exothermic reaction between the silicon and the stainless steel had resulted in the formation of liquid phase which subsequently migrated away into the surrounding steel by capillary flow. These large pores were not eliminated by the supersolidus liquid phase sintering that developed at temperatures above 1200°C. Low levels of bulk interconnected porosity, produced by sintering within the 1250-1300°C temperature range, combined with the presence of silicon, suggested that good corrosion resistance might be expected from these materials. PM/0762