Study Of CaO-MgO-Al₂O₃-SiO₂ Glass-ceramic Based Composite Coating With Good Wear And Corrosion Resistance At Elevated Temperatures

As the best common refractories, clay brick is widely used in metallurgy and chemical industries. But a mass of pores existing in the surface of clay brick reduce the strength, and the wear-resisting and corrosion resistance properties. CaO-MgO-Al₂O₃-SiO₂ glass-ceramics is a promising material because of its good wear-resisting, high strength and chemical stability properties. The CaO-MgO-Al2O3- SiO2 glass-ceramics was prepared by melting with quartz, dolomite and calcite as the starting materials and fluoride as nucleation agent. A wear-resistant ceramic coating was prepared on the surface of clay brick using glass-ceramics, bauxite and zircon as the starting materials, in order to improve the wear and corrosion resistant properties of clay brick.Experiments show that CaF₂ can effectively prompt crystallization of the glass. With the increase of CaF₂ content, crystallizing ability of the glass increases. The Avrami exponent indicates one dimensional crystal growth or the bulk crystallization. The major crystalline phases are diopside [CaMg (SiO₃)₂] and wollastonite (β-CaSiO₃). With the decrease of CaO/MgO, the content of diopside increases, resulting in the improvement of its mechanical properties.The main phases of the ceramic coating are composed of corundum (α-Al₂O₃), zircon (ZrSiO₄) and diopside [CaMg(SiO₃)₂]. The precursor glass melts over 1000℃, which is helpful for the spreading of the coating and the diffusion of other compositions. The diopside is crystallized from the melted glass during the cooling process. Microstructure of the coating and clay brick was observed by optical microscope. The coating is compact and there are no holes and cracks on the coating. The coating can be used up to 1400℃and has a Vickers hardness of 9-10GPa.