A New Approach for Refining Carbide Dimensions in M42 Super Hard High-speed Steel  

作　　者：Xue-feng ZHOU Wang-long ZHU Hong-bing JIANG Feng FANG Yi-you TU Jian-qing JIANG 

机构地区：[1]Jiangsu Key Laboratory of Advanced Metallic Materials, School of Materials Science and Engineering,Southeast University, Nanjing 211189, Jiangsu, China [2]Jiangsu Engineering Research Center of Tool and Die Steel, Danyang 212312, Jiangsu, China [3]Nanjing University of Information Science and Technology,Nanjing 210044, Jiangsu, China

出　　处：《Journal of Iron and Steel Research International》2016年第8期800-807,共8页

基　　金：Item Sponsored by National Natural Science Foundation of China(51301038,51201031,51371050);Industry-Academia-Research Program of Jiangsu Province of China(BY2014127-03);Natural Science Foundation of Jiangsu Province of China(BK20141306);Jiangsu Province Key Laboratory of High-end Structural Materials of China(hsm1404)

摘　　要：Obtaining small carbides is crucial but difficult for high-speed steels.A new approach for refining carbide dimensions in M42 super hard high-speed steel by increasing cooling rate and spheroidizing treatment was proposed.The morphologies and properties of eutectic carbides formed at different cooling rates were investigated by means of scanning electron microscopy（SEM）,energy dispersive spectroscopy（EDS）,X-ray diffraction（XRD）,transmission electron microscopy（TEM）,electron back-scattered diffraction（EBSD）and differential scanning calorimeter（DSC）.The results show that eutectic carbides change from a lamellar shape into a curved-rod shape as cooling rate increases.Despite different morphologies,the two carbides are both of M2C type with a hexagonal close-packed structure and display a single crystal orientation in one eutectic colony.The morphology of M2C mainly depends on the growing process of eutectic carbides,which is strongly influenced by cooling rate.Compared with lamellar carbides,M2C carbides with curved-rod shapes are less stable,and decompose into M6 C and MC at lower temperatures.They are more inclined to spheroidize during heating,which ultimately and distinguishably refines the carbide dimensions.As small carbides are much easier to dissolve into matrices during austenization,the process described herein improves the supersaturation of alloying elements in martensite,which leads to an increment of hardness in M42 steel.Obtaining small carbides is crucial but difficult for high-speed steels.A new approach for refining carbide dimensions in M42 super hard high-speed steel by increasing cooling rate and spheroidizing treatment was proposed.The morphologies and properties of eutectic carbides formed at different cooling rates were investigated by means of scanning electron microscopy（SEM）,energy dispersive spectroscopy（EDS）,X-ray diffraction（XRD）,transmission electron microscopy（TEM）,electron back-scattered diffraction（EBSD）and differential scanning calorimeter（DSC）.The results show that eutectic carbides change from a lamellar shape into a curved-rod shape as cooling rate increases.Despite different morphologies,the two carbides are both of M2C type with a hexagonal close-packed structure and display a single crystal orientation in one eutectic colony.The morphology of M2C mainly depends on the growing process of eutectic carbides,which is strongly influenced by cooling rate.Compared with lamellar carbides,M2C carbides with curved-rod shapes are less stable,and decompose into M6 C and MC at lower temperatures.They are more inclined to spheroidize during heating,which ultimately and distinguishably refines the carbide dimensions.As small carbides are much easier to dissolve into matrices during austenization,the process described herein improves the supersaturation of alloying elements in martensite,which leads to an increment of hardness in M42 steel.

关 键 词：eutectic lamellar hexagonal carbide heating calorimeter curved dispersive dimensions decompose 

分 类 号：TG142.1[一般工业技术—材料科学与工程]