Research On Process And Property Of Heat-resistant Grate

For the wear-resistant and heat-resistant parts working at high temperature and abrasive wear, their material not only requires high-temperature strength and enough wear resistance,but also requires good oxidation resistance to meet the demand for their performance. According to the working condition of the grates, a novel wear-resistnant and oxidation resistance alloy was prepared, which is heat-resistant and wear-resitant cast iron (we nominated RTCr28Ni15).A new production process was developed through finite element simulation. The microstructure and mechanical properties of grates at both heat treatment and as-cast condition were analyzed. Because of the disappearance of turbulent flow and the higher cooling rate, the oxide inclusions and shrinkage of casting defects reduced and the microstructure is refined. The microstructure of the alloy at as-cast are austenite and carbide. The Cr7C3 carbide has transformed into Cr23C6 carbide after heat treatment. And the microstructure is obviously thinning and uniform. The carbide exists dispersedly along the grain boundary and in the grain, which can improve the strength of the alloy. The impact toughness, tensile strength and extensibility of the new grates have better performance than the old ones.The oxidation resistance is studied on RTCr28Ni15, RTCr18Ni4 and ZGCr25Ni14 respectively at 960℃and the oxidation film of these samples are analyzed through X-ray diffraction and SEM. The results show that the rate of oxidation of the three alloys were respectively 0.0639, 0.0938 and 1.3764g.m-2.h-1 and the oxidation curves attribute to parabolic curve. The surfaces of RTCr28Ni15 and ZGCr25Ni14 have formed pretective oxidation film and the oxidation film improves the service life of material under high-temperature. Among the three heat-resistant alloys, RTCr28Ni15 of the performance of heat resistance is the best and the RTCr18Ni4 of the performance of heat resistance is the weakest. Because it's surface hasn't formed protective oxidation film, the oxidation resistance is obviously weaker than RTCr28Ni15's. After oxidation at 960℃, the oxidation film of RTCr28Ni15 consits of Cr2O3, spinel structure (FeCr2O4) and a small amount of Fe2O3 and Fe3O4.Meanwhile, the friction and wear properties of RTCr28Ni15 was compared with ZGCr25Ni14 under different load at 100℃and 270℃respectively. The amount of wear and the feature were analyzed through BMT-3D and SEM. Because of the higher consitent of carbon of RTCr28Ni15, the more hard particles were formed, which bring on the more excellent performance of wear resitance. Under low load and low temperature, the main form of wear was surface fatigue wear, and under the higher load, the main form of wear changed to adhesive wear and oxidation wear.