| With the development of thermal power generation by circulating fluidized bed boiler, there is a growing demand for high-temperature erosion wear resistant materials with better performances whereas the conventional wear resistant materials cannot fully meet the requirement any more. Therefore it is essential to devise a new sort of promising candidate erosion resistant material with high performance, low cost and long service life. This doctoral dissertation devised a metal/alloy incorporated ceramic based composite of Fe-Mo-Sialon and the relevant processing, using ferro-silicon/ferro-molybdenum alloys, alumina and silicon nitride powders as main raw materials. The processing for Fe-Mo-Sialon based biphase material was systematically studied and the effects of batch formula and sintering temperature on phase composition, mechanical properties, and microstructure were discussed. We also investigated the distribution behavior and toughening mechanism of alloy particles in Sialon matrix ceramic composite. In addition, high temperature erosion wear behaviour of Fe-Mo-Sialon material was studied by an in-house apparatus, the erosion mechanism was analyzed, and the effects of composition and structure of this material on the high-temperature erosion resistance were ascertained.Batch formula and sintering temperature have notable effects on phase composition, mechanical properties, and microstructure of the present materials. Reactive sintered FeMo-Sialon material mainly containsβ-Sialon, MoSi2 and Fe3Si phases. Fe-Sialon material is composed ofβ-Sialon and Fe3Si/FeSi2 phases. The strength of Fe-Sialon increased and Sialon grains changed to be hexagonal prismatical with increasing the sintering temperature. Micro-sized alloy particles distribute discretely in ceramic matrix and there are lots of elongated Sialon grains in the composite, which is the main reason why the Fe-Sialon material has good mechanical properties. The bending strength and Rockwell hardness of Fe-Sialon material can achieve 200-250 MPa and 75-85 HRA, which were nearly equal to those of reactive sintered Sialon and common Al2O3 ceramics.The hot-pressed FeMo-Sialon biphase material was fabricated. This material is composed ofβ-Sialon, FeMo, Mo, FeSi2 and Y-Si-Al-O-N glassy phases. The flexural strength initially increased, and then decreased with increasing FeMo70 alloy addition. The hardness decreased gradually with increasing FeMo70 alloy addition. Significantly improved toughness of Sialon based ceramic composite can be obtained by incorporation of particles. The toughness can be enhanced by 60%. The FeMo-Sialon based material with 19.3 wt.% FeMo70 alloy addition shows excellent mechanical properties and the fracture toughness, bending strength, Vickers hardness （Hv0.5） and Rock well hardness （HRA） were respectively 7.7 MPa·m1/2, 426.7 MPa, 19 GPa and88, yet those of pureβ-Sialon ceramic fabricated by the same processing were 4.9 MPa·m1/2, 320.5 MPa, 21 GPa and 91. FeMo-Sialon material shows excellent toughness and strength, as well as good hardness, which mainly depends on the interlaced elongated Sialon grains and the micro-sized alloy particles located at the boundaries of Sialon grains. Fe-Sialon biphase material was manufactured using ferro-silicon alloy and industrial-gradeα-Al2O3 powders as main raw materials by nitridize-reactive sintering. It shows excellent high temperature erosion wear resistance, better than Al2O3 ceramic, because the interlockerd elongated Sialon grains have good wear-resistant property. The erosion rate initially increases, then decreases with increasing the test temperature, and the maximum/minimum erosion occurs at 800℃/1200℃. Brittle erosion dominates the wear mechanism and material removal. The reactive sintered Fe-Sialon ceramic based material would be a promising candidate material for partially replacing Al2O3 wear resistant ceramics in some applications. |
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