Study Of B,Y-modified Pack Si Deposition Coating On Molybdenum

Refractory metals Mo has broad application prospects in aviation, aerospace,electronics and metallurgical industries, owing to its high melting point, good thermalconductivity and good corrosion resistance. However, it’s easily to be oxidized at above400℃in oxidizing environment, which severely restricted its use in the field of high-temperature materials. In this paper, pack cementation process has been used for preparingMo-Si-B system coating on the Mo substrate to improve the antioxidant properties of thematrix. And the effect of various experimental parameters on tissue formation of the packcementation coatings has been studied. In addition, the effect of Y adding in the packcementation agent on organizational structure and oxidation resistance of the coating hasbeen studied too. XRD, EDS, WDS techniques were used to detect the phase structure andcomposition of the coatings.The results reveal that the Si-B co-deposition coatings have a5-layer structure. Fromsurface to substrate, the coating can be divided into the MoSi2out layer, the MoSi2+MoBsecond layer, the Mo5Si3third layer, the MoB fourth layer and the Mo2B inner layer. Thegrowth of the coating is dominated by the inward diffusion of Si and B.With highertemperature, the growth rate of the coating is accelerated. And the growth of MoSi2follows a parabolic law. Different amounts of B in penetration enhancers has a minorimpact on the organizational structure of the coating. Y-modified Si-B co-depositioncoating and the Si-B co-deposition coating have the same structure. However, with theaddition of Y gradually increase in penetration from0.5-8wt.%, the growth of the coatingincrease first and then decrease and the effect is maximum when the content of Y is2wt.%.The results of oxidation at600and1250℃reveals that both Si-B co-deposition and Y-modified Si-B co-deposition coating have a excellent oxidation resistance. Oxidation ofthe Si-B co-deposition coating reveals that B atoms can diffuse outward to coating surfaceand oxidize to B2O3, which can promote the formation of a dense scale. The results ofcyclic oxidation at1000℃for100h reveals that compared with the Si-B co-depositioncoating Y-modified Si-B co-deposition coating has better oxidation resistance.