Carbonized transition layer mediated controllable and uniform growth of diamond film on zirconia substrate

Zirconia (ZrO₂) ceramics are advanced inorganic non-metallic materials widely used in aerospace, nuclear, and marine applications owing to their excellent mechanical and thermal properties. To enhance their tribological performance, protective coatings with high hardness, low friction, and corrosion resistance are required. Diamond films are attractive candidates due to their outstanding hardness, wear resistance, chemical inertness, and thermal conductivity. However, the large mismatch in thermal expansion coefficients between ZrO₂ (10.5 × 10⁻⁶/K) and diamond (0.8 × 10⁻⁶/K) results in severe residual stresses and poor interfacial adhesion, which limits their integration.

Interface engineering with transition layers has been shown to improve diamond nucleation and adhesion on non-carbide substrates. Previous studies demonstrated effective strategies such as Mo/Mo-N, VC, and Q-carbon interlayers on steel, yet little progress has been made on ZrO₂. Unlike carbide-forming substrates (e.g., WC, Si), zirconia is chemically stable and does not readily form carbide bonding phases, posing an additional challenge.

Recently a two-step strategy was proposed to achieve high-quality diamond coatings on zirconia ceramics. First, a high-adhesion Si transition layer was deposited and evaluated under high-temperature thermal cycling to simulate diamond growth conditions. Second, the Si layer surface was carbonized to form SiC, thereby enhancing diamond nucleation density and enabling uniform, stable growth of the diamond film. This approach demonstrates that although zirconia cannot directly form carbides, diamond films can be effectively integrated via interlayer regulation, providing a promising route for developing zirconia–diamond composite coatings with broad potential in advanced engineering applications.