Abstract
The 0.1Al2O3-ZrO2 reinforced MoSi2 composite coating was prepared on pure Mo substrate to improve its high-temperature oxidation resistance, of which the MoSi2 coating was prepared by a modified pack siliconizing process and subsequently the 0.1Al2O3-ZrO2 layer was generated on the as-prepared MoSi2 layer by a non-hydrolytic sol-gel method. The phase composition and microstructure of the as-prepared composite coating before and after oxidation exposure were investigated by XRD, SEM and EDS. Different from the loose structure of the single MoSi2 coating after oxidation exposure, the 0.1Al2O3-ZrO2 reinforced MoSi2 composite coating exhibited a relatively compact internal structure with less through-thickness cracks. The introduction of 0.1Al2O3-ZrO2 layer effectively prevented the cracking and spalling of the glassy SiO2 scale formed on the surface of MoSi2 during the oxidation, and then the SiO2 scale could be well stabilized on the coating surface. The protective SiO2 glassy scale embedded with stable ZrO2 and ZrSiO4 phase was formed, contributing to the improvement in the structure stability of the composite coating. It was proposed that ZrO2, ZrSiO4 and SiO2 developed a special glass-ceramic skeleton structure, in which ZrO2 and ZrSiO4 played the role of “Zr nail” to the SiO2 scale. In addition, the reinforcement mechanism of 0.1Al2O3-ZrO2 layer to the MoSi2 coating was also discussed.
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