Weiping Zhang, Lijing Zhang, Yanqiang Qiao, Xiping Guo
MoSi 2 coatings fabricated via conventional single-step slurry sintering typically suffer from high porosity and insufficient oxidation resistance. To address this limitation, a Mo-Si/Cr-Si composite slurry was designed in this work, enabling the successful fabrication of a dense MoSi 2 coating with a metallurgically bonded interface on Nb-Si-based alloy through a single-step sintering process. The coating formation mechanism was systematically investigated. During sintering, a lamellar CrSi interlayer preferentially formed from the Cr-Si slurry layer, which effectively suppressed the inward diffusion of Si from Mo-Si slurry, thereby promoting the densification of the outer MoSi 2 layer. Subsequently, at elevated temperatures, this interlayer softened and underwent elemental interdiffusion with adjacent layers, ultimately achieving an interfacial metallurgical bonding. As a result, the coating forms a three-layer structure consisting of an outer MoSi 2 layer, an intermediate (Mo, Cr) 5 Si 3 layer, and an inner (Nb, X) 5 Si 3 transition layer. The coating exhibits excellent isothermal oxidation resistance at both 1250 and 1350 °C, as well as good thermal cycling resistance at 1250 °C. Such superior performances are attributed to its dense microstructure, metallurgically bonded interface, and the consequent formation of a continuous and dense SiO 2 protective scale. This study provides an effective, low-cost strategy for fabricating high-performance MoSi 2 coating on Nb-Si-based alloy.