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采用喷射成形技术制备了M3型高速钢和以Nb替代V的M3型高速钢.利用扫描电镜、X射线衍射、差示扫描量热仪和金相显微镜研究了Nb对M3型高速钢组织的影响.喷射成形能有效消除宏观偏析,细化组织.以Nb代V,提高了MC型碳化物开始析出温度,大量MC相先于共晶反应析出,呈独立的近球形分布于晶界,同时其尺寸减小.由于消耗大量C,抑制了共晶反应,M2C片层数量减少且厚度变薄,其在热变形过程中更易于分解,进一步增加了组织均匀性.低温低载荷时含铌的M3型高速钢抗磨损性能显著优于M3高速钢,温度升高到500℃时磨损机制逐渐以氧化磨损为主,两合金的抗磨损性能差距减小,主要原因是大量呈弥散球形分布的含铌MC型碳化物能有效提高高速钢的磨粒磨损抗性,而其对抗氧化性能并无明显作用.
M3 high-speed steel and M3 high-speed steel with Nb instead of V were prepared by spray forming technique.The effects of Nb on the microstructure of M3 high-speed steel were studied by scanning electron microscopy, X-ray diffraction, differential scanning calorimetry and metallographic microscope Spray forming can effectively eliminate the macroscopic segregation and refinement of the microstructure.With Nb on behalf of V, the onset temperature of MC carbides increases, and a large amount of MC phase precipitates before the eutectic reaction and forms an independent near spherical distribution in the grain boundaries, The size of M2C is reduced and the eutectic reaction is restrained due to the consumption of a large amount of C. The number of M2C lamellae decreases and the thickness becomes thinner so that it is more easily decomposed during the thermal deformation and further improves the homogeneity of the microstructure. The wear resistance of high-speed steel is obviously better than that of M3 high-speed steel. The wear mechanism is gradually oxidized and wear-resistant when the temperature is increased to 500 ℃. The gap between the two alloys decreases. The main reason is that a large number of niobium MC carbides can effectively improve the abrasive wear resistance of high-speed steel, and its oxidation resistance has no significant effect.