MoSi2 and (Mo,W)Si2 coatings were prepared on Mo and Mo?W substrates respectively by means of pack cementation, and the effects and mechanisms of W element doping on the oxidation resistances of MoSi2 coating were investigated systematically. XRD, SEM and EDS were used to determine the phase structure, morphology and composition of the coatings. The results showed that W element was dissolved in MoSi2 coating in the form of (Mo,W)Si2 solid solution, and the microstructure of (Mo,W)Si2 coating was denser compared with that of MoSi2 coating as a result of W element doping. After static oxidation at 1600℃, the antioxidant life of (Mo,W)Si2 coating reached 70 h, while MoSi2 coating was failed after 25 h oxidation due to severe weight loss. Moreover, (Mo,W)Si2 coating exhibited excellent high-temperature protection performance after oxidation at 1200℃ for 1000 h. At the initial stage of the oxidation, the oxidation rate of (Mo,W)Si2 coating was higher than that of MoSi2 coating owing to W element doping, which led to lower formation velocity of dense oxide layer on the surface of (Mo,W)Si2 coating. After the dense SiO2 covering the surface completely, the oxidation rate of (Mo,W)Si2 coating decreased dramatically. The diffusion reaction between the Si element and the substrate was hindered by the addition of W element, the consumption rate of Si element in the coating was reduced remarkably, and the high-temperature oxidation resistance of (Mo,W)Si2 coating was enhanced significantly. After static oxidation at 500℃, comparing with MoSi2 coating, (Mo,W)Si2 coating exhibited a typical “Pest” phenomenon after oxidation for 50 h, and the coating failed in the form of disintegration. The addition of W element reduced the diffusion rate of Si element in the coating, therefore, a dense oxide layer could not be formed on the coating surface at low-temperature, which caused the rapid oxidation of the coating.
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