Microstructure formation mechanism of Mo2C/W2C/Mo2C three-layer film on Mo substrate prepared by magnetron sputtering and carburization

Abstract

This work presents a new concept for preparing ceramic multilayers: carburization of refractory metal multilayers. Unlike the direct deposition of ceramic multilayers, we prepared a Mo/W multilayer film on a Mo substrate using magnetron sputtering and then carburized the sample to obtain a Mo₂C/W₂C ceramic multilayer film. The simplest ceramic three-layer film is the main research object of this work. Our study shows that, during the carburization, the carbide layers grew inward with two ceramic/metal carburization frontiers, with the Mo₂C/Mo frontier leading the W₂C/W frontier. W₂C can grow epitaxially on the Mo₂C grains without nucleation, forming columnar grains of half Mo₂C and half W₂C across the interlayer interface. The ceramic three-layer film was nonporous, and there was a significant interdiffusion of Mo and W elements at the interlayer interfaces, and the final film-substrate interface was the Mo₂C/Mo interface located inside the initial Mo substrate. The hardness of the ceramic film with a thickness of 5.5–7.5 μm was about 1500–1600 HV. The peeling of the outermost Mo₂C layer started at 42 N, and the peeling of the W₂C layer occurred at 90 N, but the inner Mo₂C layer was not peeled at 90 N.