Microstructure and oxidation behaviors at 800°C and 1250°C of MoSi ₂ /ReSi ₂ /NbSi ₂ compound coating prepared by electrodeposition and then pack cementation

Mo[sbnd]Re duplex film has been electrodeposited from aqueous solution innovatively and then applied to fabricate protective silicide coating for the Nb[sbnd]Ti[sbnd]Si based alloy successively. The XRD, SEM and EDS results indicated the formation of MoSi ₂ /ReSi ₂ /NbSi ₂ compound coating after halide reactivated pack cementation (HAPC) treatment. Pesting oxidation of MoSi ₂ layer was suppressed and the Nb[sbnd]Ti[sbnd]Si based alloy was effectively protected at 800 °C with a mass gain of 0.48 mg cm ⁻² after oxidation for 100 h. At 1250 °C, continuous mass gain was observed with a mass gain of 2.6 mg cm ⁻² after exposure of 10 h. The synergistic combination of MoSi ₂ and NbSi ₂ layer enabled admirable protection of the substrate, in which MoSi ₂ layer worked as the major anti-oxidation coating and the NbSi ₂ layer could be a reservoir for Si. The contrast experiments indicate that ReSi ₂ layer could improve the integrity and adherence of MoSi ₂ layer, reduce the outward diffusion of alloying elements and oxidation of NbSi ₂ layer, and then improve oxidation resistance of the compound coating ultimately.