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

The physical and chemical stabilities of SiC and heat-resistant steel were assessed by the diffusion couple method under vacuum at 1200 degrees 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. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).