Oxidation behavior and adhesion performance of TiSi₂–NbSi₂ composite coating prepared via magnetron sputtering and then pack cementation

A TiSi₂–NbSi₂ composite coating has been successfully prepared on Nb–Si based ultrahigh temperature alloys via firstly magnetron sputtering a Ti–5Al–10Nb–2Zr (at.%) thin film and then Si–Y co-deposition. The composite coating contains a TiSi₂ outer layer, an NbSi₂ inner layer and a thin transitional layer. The mass gain of the TiSi₂–NbSi₂ composite coating after oxidation at 1250 °C for 100 h is 2.7 mg/cm², lower than that of the simple silicide coating (4.2 mg/cm²), because the addition of Zr in the coating promotes the formation of a denser and thinner glass-like scale and inhibits the severe outward diffusion of metal ions. The scratch tests show that the coating has bound with the substrate very tightly due to metallurgical bonding in the coating.