Influences of early-stage C diffusion on growth microstructures in solid-state interface reaction between CVD diamond and sputtered Cr

In this work, the influence of early-stage C diffusion on the microstructures of chromium carbides formed in solid-state (S/S) interface reaction between (100) plane of CVD diamond and sputtered Cr was comprehended using XPS and TEM techniques. It was evidenced the catalytically converted disordered carbon (DC) was the first phase formed in early-stage S/S reaction. An abnormal C diffusion in sputtered Cr was observed for the first time, which is due to the pinning effect of Cr surface on C diffusion and consequently influences the interfacial microstructures. Formation behaviors of Cr7C3 and Cr23C6 carbides were examined and the latter was found to be the dominant phase formed in the S/S interface reaction at 500 and 600 °C. The origin and evolution of crystal twins at grain boundaries between interfacial carbides were unveiled using HRTEM. The concentration of internal strain at diamond and carbides interface in the ripening process was quasi-quantitively assessed using windowed Fourier Transform-Geometric Phase Analysis (WFT-GPA) method. It has been found the concentration of internal strain was largely ameliorated when a coherent-like interface was formed between diamond and chromium carbides. Results reported in this work are of fundamental importance to understand the bonding mechanisms of diamond and allow the optimization of process parameters to achieve a microstructure of metal matrix composites (MMCs) materials with desirable properties.