The morphologies and formation process of Ni-pool defects in WC?8Ni cemented carbides were studied. The SEM images show that Ni-pool generally has two kinds of morphologies: “island” in isolation and “ring” around...The morphologies and formation process of Ni-pool defects in WC?8Ni cemented carbides were studied. The SEM images show that Ni-pool generally has two kinds of morphologies: “island” in isolation and “ring” around a new phase. In the obtained samples with “ring-like Ni-pool”, WC, Ni and Ni2W4C (η phase) phases were detected in XRD patterns. Combined with SEM, EDX and XRD results, it is found that the phase in the center of the “ring-like Ni-pool” is Ni2W4C (η phase) and the main chemical components of Ni-pool are Ni, W and C. In addition, the relationships among large size Ni (agglomerated) particles, volatile impurities, pores and carbon content vs forming process of the Ni-pool defects for WC?8Ni cemented carbides are also presented and discussed.展开更多
Two types of commercial WC-Ni samples were irradiated with the High-intensity pulsed ion beam(HIPIB).Both the surface characteristics and tribo-characteristics of the non-irradiated and irradiated WC-Ni samples,slidin...Two types of commercial WC-Ni samples were irradiated with the High-intensity pulsed ion beam(HIPIB).Both the surface characteristics and tribo-characteristics of the non-irradiated and irradiated WC-Ni samples,sliding against graphite under water lubrication,were compared.Quite low steady friction coefficients(approximately of 0.02) of the irradiated WC-Ni were observed.The surface topographies and components were investigated.The quite low friction of the irradiated WC-Ni samples was ascribed to the higher fluid retention capability of the latter and the tribofilm formed during sliding.展开更多
Laser cladding is performed to improve the surface properties of metallic machine components. Extensive work is being conducted to investigate the relationships among the cladding parameters, clad powder characteristi...Laser cladding is performed to improve the surface properties of metallic machine components. Extensive work is being conducted to investigate the relationships among the cladding parameters, clad powder characteristics and the quality of the clad layer. This work presents some of the metallographic analyses results of WC -Ni and WC-Co clad layers. The clad layers are characterised with non-uniform carbide particles, mostly WC imbedded in a more ductile matrix. The transition from the clad layer to the substrate metal had a distinct dilution zone. The ratio of this zone to the clad height was in the range of 10 -12% and this still needs to be refined.展开更多
Ni nanoparticles were coated uniformly on the surface of WC powder via a facile electroless plating method(abbreviated as WCN-EP),and then consolidated for mechanical and corrosion resistance performance characterizat...Ni nanoparticles were coated uniformly on the surface of WC powder via a facile electroless plating method(abbreviated as WCN-EP),and then consolidated for mechanical and corrosion resistance performance characterization,in comparison with hand mixed WC-Ni(WCN-H).Under the optimized electroless plating parameters,Ni particles,less than 1μm in average diameter,were found to be uniformly and densely wrapped on the surface of the tungsten carbide matrix of WCN-EP.In comparison,in WCN-H,the Ni particles about 1.8μm in average diameter,were randomly distributed together with irregular WC particles.The uniform coating of Ni was found to assist the densification process of WCN-EP effectively,with higher densities and less pores than those of WCN-H at the Ni content of 10.6wt%,25.5wt%,and 30.3 wt%.However,at the Ni content of 18.8wt%,the relative densities of WCN-EP and WCN-H both increased to the maximum value of 98%.The maximum hardness of the consolidated WCN-EP was 82.6 HRA,about 1.2 HRA higher than that of WCN-H.In addition,the consolidated WCN-EP also exhibits a superior corrosion resistance by the polarization curve analysis at an electrochemical workstation.展开更多
文摘The morphologies and formation process of Ni-pool defects in WC?8Ni cemented carbides were studied. The SEM images show that Ni-pool generally has two kinds of morphologies: “island” in isolation and “ring” around a new phase. In the obtained samples with “ring-like Ni-pool”, WC, Ni and Ni2W4C (η phase) phases were detected in XRD patterns. Combined with SEM, EDX and XRD results, it is found that the phase in the center of the “ring-like Ni-pool” is Ni2W4C (η phase) and the main chemical components of Ni-pool are Ni, W and C. In addition, the relationships among large size Ni (agglomerated) particles, volatile impurities, pores and carbon content vs forming process of the Ni-pool defects for WC?8Ni cemented carbides are also presented and discussed.
基金financially supported by both the National Basic Research Program of China(973)(Grant No.2015CB057303)the National Natural Science Foundation of China(Grant No.51275268)
文摘Two types of commercial WC-Ni samples were irradiated with the High-intensity pulsed ion beam(HIPIB).Both the surface characteristics and tribo-characteristics of the non-irradiated and irradiated WC-Ni samples,sliding against graphite under water lubrication,were compared.Quite low steady friction coefficients(approximately of 0.02) of the irradiated WC-Ni were observed.The surface topographies and components were investigated.The quite low friction of the irradiated WC-Ni samples was ascribed to the higher fluid retention capability of the latter and the tribofilm formed during sliding.
文摘Laser cladding is performed to improve the surface properties of metallic machine components. Extensive work is being conducted to investigate the relationships among the cladding parameters, clad powder characteristics and the quality of the clad layer. This work presents some of the metallographic analyses results of WC -Ni and WC-Co clad layers. The clad layers are characterised with non-uniform carbide particles, mostly WC imbedded in a more ductile matrix. The transition from the clad layer to the substrate metal had a distinct dilution zone. The ratio of this zone to the clad height was in the range of 10 -12% and this still needs to be refined.
基金Funded by the National Natural Science Foundation of China(Nos.51778213 and 52078189)the Fundamental Research Funds for the Central Universities of China(No.B200202073)。
文摘Ni nanoparticles were coated uniformly on the surface of WC powder via a facile electroless plating method(abbreviated as WCN-EP),and then consolidated for mechanical and corrosion resistance performance characterization,in comparison with hand mixed WC-Ni(WCN-H).Under the optimized electroless plating parameters,Ni particles,less than 1μm in average diameter,were found to be uniformly and densely wrapped on the surface of the tungsten carbide matrix of WCN-EP.In comparison,in WCN-H,the Ni particles about 1.8μm in average diameter,were randomly distributed together with irregular WC particles.The uniform coating of Ni was found to assist the densification process of WCN-EP effectively,with higher densities and less pores than those of WCN-H at the Ni content of 10.6wt%,25.5wt%,and 30.3 wt%.However,at the Ni content of 18.8wt%,the relative densities of WCN-EP and WCN-H both increased to the maximum value of 98%.The maximum hardness of the consolidated WCN-EP was 82.6 HRA,about 1.2 HRA higher than that of WCN-H.In addition,the consolidated WCN-EP also exhibits a superior corrosion resistance by the polarization curve analysis at an electrochemical workstation.
