Microstructure and phase transformation behavior of Mo–MoSi2 gradient material

Abstract

Mo-MoSi 2 gradient coating on Mo substrate was prepared by siliconizing process, using the polysilicon as silicon atoms. The gradient layer was analyzed by the experimental results, theoretical analysis, and thermodynamic calculation. The silicon, molybdenum content of gradient coating shows a gradual change regulation. The reaction between silicon and molybdenum is most likely to generate Mo 5 Si 3 , then MoSi 2 , finally Mo 3 Si, but when the silicon content is excessive, the Mo 5 Si 3 and Mo 3 Si will react with silicon and generate MoSi 2 . The gradient layer is mainly constituted by Si and MoSi 2 , only about 1/10 gradient layer is constituted by Mo 5 Si 3 and Mo 3 Si, and the stable existences of Mo 5 Si 3 and Mo 3 Si are mainly determined by the silicon content. Along the Mo substrate to the surface of the coating, the phase composition of gradient coating changes as follows: Mo ? transition layer, Mo (main phase) ? Mo 3 Si ? Mo 5 Si 3 ? intermediate layer, and MoSi 2 (main phase) ? Mo 5 Si 3 ? Si ? surface layer MoSi 2 (main phase) ? Si, and the experimental temperature has no effect on phase composition of gradient coating.

Mo–Si–B alloys for ultra-high-temperature space and ground applications: liquid-assisted fabrication under various temperature and time conditions

“…The authors documented that functionally graded MoSi2-Mo coatings produced by the proposed method show an excellent oxidation resistance and a good bonding with Mo substrates. They also observed that the morphology of MoSi2-Mo products might be also easily controlled by adjusting the hot-dipping process parameters [17,18].…”