Thermal decomposition of silicon carbide in a plasma-sprayed Cu/SiC composite deposit

A functionally graded SiC/Cu metal matrix composite (MMC) produced by plasma spray has been studied. The phase constituents of Cu, Cu2O, CuO, Cu3Si, Si, and SiC in the plasma-sprayed deposits were analyzed by XRD. The SiC was decomposed into Si and C, and copper silicide was then formed. Most pores were found in the vicinity of SiC due to the decomposition of the SiC and thermal expansion mismatch between SiC and Cu during rapid solidification. From the thermodynamic consideration, the overall decomposition of SiC during plasma spray process occurs as follows: (1) SiC(s) = Si(s) + C(s); (2) SiC(s) + CO2(g) = Si(s, l) + 2CO(g) and SiC(s) + 2CO(g) = SiO2(s) + 3C(s); (3) SiO2(s) + CO(g) = Si(s, l) + 2CO2(g). Based on the analyses of the electron probe X-ray microscope analyzer (EPMA) and X-ray photoelectron spectroscopy (XPS), it was revealed that dissociated carbon was present in the deposits.