The Time and Temperature Dependence of AISI 316L Corrosion in Chlorosilane Environments

Monday, 25 May 2015: 13:40
PDR 2 (Hilton Chicago)
J. L. Aller, K. Ellingwood (Montana State University), B. Clark (GT Advanced Technologies), and P. E. Gannon (Montana State University)
Chlorosilanes are used abundantly at high temperatures in the production of ultra-pure silicon and silicon containing materials. The presence of both chlorine and silicon presents a unique corrosion environment for the metallic materials that must handle these compounds. It is known that in chlorosilane environments, 316L can form either a protective metal silicide layer or a volatile metal chloride layer on the substrate. However, it is not known what dependence this surface reaction has on temperature, time, or gas composition. In this study, AISI 316L stainless steel was exposed to vaporized silicon tetrachloride (STC, SiCl4), pure hydrogen (H2), and anhydrous hydrogen chloride (HCl) at temperatures (>500°C), times (1-150 hours), and compositions relevant to industrial processes. Metal silicide and metal chloride formation was evaluated using surface and gravimetric analysis, with metal silicide formation causing a gain in sample mass and metal chloride formation causing a loss in sample mass. It was revealed that the transition between chloride and silicide formation depends on time of exposure, temperature, and mole fraction of HCl present in the gas stream. Lastly, some discussion is provided on the underlying mechanisms of silicide and chloride formation, and how to prevent excessive corrosion in industrial applications.