Microstructure and mechanical properties of Ni-alloyed SiC coatings

SiCNi composite coatings were synthesized by non-reactive magnetron co-sputtering from SiC and Ni targets. Chemical composition of the coatings was analyzed by X-ray energy dispersive spectrometer. The structure of the coatings was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. All coatings were found to be amorphous and dense structure. An interconnected nanostructure with two phases which are considered to be SiC-rich phase and NiSix-rich phase, is evident in the coating with 12.5 at.% Ni. Mechanical properties of the samples were tested using nanoindentation. The hardness of the coatings ranging from 29 GPa to 20 GPa, decreased steadily with the increase of Ni content. An enhanced toughness proved by the scratch tests was obtained for the coating with 12.5 at.% Ni. And the improvement of toughness might be attributed to the interconnected nanostructure.