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Cubic silicon carbide (β-SiC) thin films were synthesized on cemented carbide (WC–Co) substrates as an interlayer for modifying the adhesion of diamond coatings. The influence of varying the hydrogen (H 2 )/tetramethylsilane (TMS) flow ratios on the microstructure, phase composition and adhesion of the β-SiC films was investigated. It was found that with the increase of the H 2 /TMS flow ratios, the SiC crystallite size increases from 6.5 nm to 22.2 nm. When the flow ratio was 40:5, the film was formed of loose cauliflower-like agglomerates, containing SiC granular particles. With the flow ratio increased from 40:5 to 120:5, the films became more uniform and denser, resulting in adhesion enhancement. However, when the ratio increased from 160:5 to 200:5, clusters composed of faceted particles replaced the agglomerates, and the adhesion reduced. The β-SiC film deposited with a H 2 /TMS flow ratio of 120:5 possessed a more uniform and denser structure, as well as better adhesion than the others. After subsequent diamond deposition, homogeneous nanocrystalline diamond coatings were realized on the β-SiC interlayered substrates. Compared with the results on the well-known two-step chemically etched substrates, the diamond coatings deposited on the substrates with the β-SiC interlayer possess excellent adhesion. It was also validated in this research that the β-SiC interlayer deposited with a H 2 /TMS flow ratio of 120:5 was effective in enhancing the adhesion of diamond coatings prepared on WC–Co substrates. [ABSTRACT FROM AUTHOR]