The volume fraction of the lamellar carbide cell in HK50 alloy may be increased with the in- crease of nitrogen content over 0.065%.The habit plane of l(?)mellar carbide is {111}_γ.The distribution of nitrogen change...The volume fraction of the lamellar carbide cell in HK50 alloy may be increased with the in- crease of nitrogen content over 0.065%.The habit plane of l(?)mellar carbide is {111}_γ.The distribution of nitrogen changes no more before or after the precipitation of lamellar structure. The diffusion activation energy of carbon reduces remarkably with the increase of nitrogen content.It is believed that the lamellar carbide cell is harmful to the high temperature creep and impact properties of the alloy.展开更多
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 prop...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.展开更多
文摘The volume fraction of the lamellar carbide cell in HK50 alloy may be increased with the in- crease of nitrogen content over 0.065%.The habit plane of l(?)mellar carbide is {111}_γ.The distribution of nitrogen changes no more before or after the precipitation of lamellar structure. The diffusion activation energy of carbon reduces remarkably with the increase of nitrogen content.It is believed that the lamellar carbide cell is harmful to the high temperature creep and impact properties of the alloy.
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)+1 种基金Natural Science Foundation of Jiangsu Province of China(BK20141306)Jiangsu Province Key Laboratory of High-end Structural Materials of China(hsm1404)
文摘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.
