Thermo-Mechanical Properties of Interface Reaction Phases in Cr Coating on Sic Substrate:A First-Principles Investigation

Abstract

The issue of hydrothermal corrosion in silicon-fiber reinforced silicon carbide-based ceramic composite (SiCf/SiC) fuel cladding for light water reactors (LWRs) can potentially be addressed by utilizing a chromium (Cr) corrosion barrier coating. However, the mechanism of interface reaction between the Cr coating and SiC substrate at elevated temperatures remains unclear. In this study, we investigated lattice structures, elastic mechanisms, and thermodynamic parameters using density functional theory (DFT). Our calculations have indicate that the carbide phase exhibits ductility while the silicide phase is brittle. Among them, Cr3C2 with maximum B and G values shows lower resistance to cracking. The melting points of both carbide phases and silicide phases are lower than that of SiC bulk but higher than that of Cr bulk. It is crucial to carefully consider temperature design margins to meet safety criteria for fuel cladding in LWRs. Additionally, except for the Cr7C3 phase, linear thermal expansion coefficients (α) for both carbide phases and silicide phases lie between those of SiC and Cr. This suggests that interface reaction phases may have an impact on mechanical stability at interfaces.

Keywords: accident tolerant fuel, coating, Interface Phases, Mechanical Properties