Interfacial reaction mechanism and high temperature stability of heat-resistant steel and SiC under a vacuum environment

Abstract

The physical and chemical stabilities of SiC and heat-resistant steel were assessed by the diffusion couple method under vacuum at 1200 °C, which is a commonly used condition in magnesium metallurgy. High-temperature visualization instruments were used and Differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermodynamic analyses were performed to verify the relevant mechanism. The reaction between SiC and heat-resistant steel can be divided into two stages: solid–solid and solid–liquid reactions. The solid–solid interfacial reaction produces graphite, which hinders the interfacial reaction. The interfacial reaction simultaneously generates silicides (NiSi, Ni2Si, and Ni3Si) with low melting points and transforms the reaction interface into a solid–liquid interface. The formation of the liquid phase promotes the dissolution and diffusion of carbon, leading to the accelerated corrosion of SiC and low-temperature melting of steel. Supersaturated carbon precipitates in the melt in the form of nanowires or nanotubes are catalyzed by Fe/Ni. Herein, a general model describing the direct interfacial reaction mechanism of SiC and heat-resistant steel is proposed to explain the reaction process under vacuum.