Preparation of high bonding strength C-SiC composite coatings on single crystal Si substrate by extra-C source method

The C-SiC composite coating is integrally prepared on the surface of a single-crystal Si（100） substrate using chemical vapor deposition（CVD） with graphite as the extra-C source and HMDSO-H2 as the precursor system. The surface morphology， phase composition， mechanical properties， and thermal shock resistance of the composite coatings are analyzed by scanning electron microscopy（SEM）， X-ray diffraction（XRD）， nanoindentation and scratch testing. The results show that the extra-C source enable simultaneous deposition of a carbon buffer layer and SiC coating. The prepared C-SiC composite coating exhibits a total thickness of 50 μm （including a 10 μm-thick C buffer layer）， dense structure， and excellent adhesion to the single-crystal Si substrate. The coating shows outstanding thermal shock resistance， with surface cracks emerging after 20 thermal cycles between 20 ℃ and 1200 ℃， but no warping or delamination occurs. The nanoindentation reveals that hardness and elastic modulus of the composite coating are 23.25 GPa and 272.3 GPa， respectively， while the scratch testing indicates an interfacial adhesion strength between the coating and substrate is 29 N.