The Fe-based composite coatings were produced on the attrition spot of cutting pick by plasma jet surface metallurgy, and metallurgical bonding was obtained between coating and substrate. The results show that the mic...The Fe-based composite coatings were produced on the attrition spot of cutting pick by plasma jet surface metallurgy, and metallurgical bonding was obtained between coating and substrate. The results show that the microstructure, microhardness, wear resistance and erode resistance of the coating are all evaluated. The coating has apparent characteristics of rapid and layered crystallization from planar crystal-cell/dendritic transition zone on the interface, to equiaxed crystal on the midst, to spike crystal on the surface. The microhardness gradually increases from the bottom to the top of the coating. The composite coating has better wear resistance and erode resistance compared to steel substrate.展开更多
Metallurgical coatings of iron-based alloy with RE oxide were prepared on low-carbon steel using a home-made DC-plasma jet surface metallurgy equipment. Scanning electron microscope (SEM), energy dispersive X-ray (EDX...Metallurgical coatings of iron-based alloy with RE oxide were prepared on low-carbon steel using a home-made DC-plasma jet surface metallurgy equipment. Scanning electron microscope (SEM), energy dispersive X-ray (EDX) microanalysis and X-ray diffraction analysis (XRD) were employed to observe the microstructure and analyze the chemical compositions of coatings. And the cracking susceptibility of coatings was studied in terms of RE addition. Experimental results show that addition of RE oxide (La_2O_3 and CeO_2) can refine and purify the microstructure, and can reduce the cracking susceptibility of coatings.展开更多
Optical emission spectroscopy （OES） was used to study the gas phase composition near the substrate surface during diamond deposition by high-power DC arc plasma jet chemical vapor deposition （CVD）. C2 radical was ...Optical emission spectroscopy （OES） was used to study the gas phase composition near the substrate surface during diamond deposition by high-power DC arc plasma jet chemical vapor deposition （CVD）. C2 radical was determined as the main carbon radical in this plasma atmosphere. The deposition parameters, such as substrate temperature, anode-substrate distance, methane concentration, and gas flow rate, were inspected to find out the influence on the gas phase. A strong dependence of the concentrations and distribution of radicals on substrate temperature was confirmed by the design of experiments （DOE）. An explanation for this dependence could be that radicals near the substrate surface may have additional ionization or dissociation and also have recombination, or are consumed on the substrate surface where chemical reactions occur.展开更多
The technical connotation of surface metallurgical technology by DC-Plasma-Jet is a kind of rapid, non- equilibrium metallurgical process which is similar to powder metallurgy. Accordingly the specialized equipment is...The technical connotation of surface metallurgical technology by DC-Plasma-Jet is a kind of rapid, non- equilibrium metallurgical process which is similar to powder metallurgy. Accordingly the specialized equipment is developed all by ourselves, which is not subjected to limitation of solubility, melting point, density of constituents, therefore pre-alloy powders are not needed. The plasma surface metallurgical coating using Fe-Cr-C-Ni-B-Si mixed alloy powders has good wettability with substrate material. The metallurgical coating has apparent characteristics of rapid and layered crystallization from planar crystal-cell to dendritic transition zone at the interface, from dendritic crystal to equiaxed crystal in the midst, from equiaxed crystal to spike crystal on the surface. Its metastable microstructure is complex phase of supersaturated γ- （ Fe, Ni ） dendritic crystal solutioning great amount of alloy element and interdendritic eutectic structure （ Cr, Fe） γ （ C, B） 3 and T-（Fe,Ni）.展开更多
DC plasma is a very promising technology for processing different materials, and is becoming especially interesting when low environmental impact and high-performance treatments are needed. Some of the intrinsic chara...DC plasma is a very promising technology for processing different materials, and is becoming especially interesting when low environmental impact and high-performance treatments are needed. Some of the intrinsic characteristics of DC plasma technology, which make it suitable for powder metallurgy （PM） and powder injection molding （PIM） parts production, are low- pressure processing and plasma environment high reactivity. Moreover it can be considered as a highly competitive green technology. In this work, an overview of some of the important DC plasma techniques applied to PM and PIM parts processing is presented. Emphasis is given to the descriptions of the main characteristics and the technique potentials of plasma-assisted nitriding, plasma-assisted thermal debinding, plasma-assisted sintering, and simultaneously plasma-assisted sintering and surface alloying. The aspects presented and discussed in this paper indicate that DC plasma processes are promising and competitive techniques for PM and PIM parts processing.展开更多
基金Project(50801032) supported by the National Natural Science Foundation of ChinaProject(2008GQC0027) supported by the Natural Science Foundation of Jiangxi Province, ChinaProject(GJJ08270) supported by the Foundation of Education Office of Jiangxi Province, China
文摘The Fe-based composite coatings were produced on the attrition spot of cutting pick by plasma jet surface metallurgy, and metallurgical bonding was obtained between coating and substrate. The results show that the microstructure, microhardness, wear resistance and erode resistance of the coating are all evaluated. The coating has apparent characteristics of rapid and layered crystallization from planar crystal-cell/dendritic transition zone on the interface, to equiaxed crystal on the midst, to spike crystal on the surface. The microhardness gradually increases from the bottom to the top of the coating. The composite coating has better wear resistance and erode resistance compared to steel substrate.
文摘Metallurgical coatings of iron-based alloy with RE oxide were prepared on low-carbon steel using a home-made DC-plasma jet surface metallurgy equipment. Scanning electron microscope (SEM), energy dispersive X-ray (EDX) microanalysis and X-ray diffraction analysis (XRD) were employed to observe the microstructure and analyze the chemical compositions of coatings. And the cracking susceptibility of coatings was studied in terms of RE addition. Experimental results show that addition of RE oxide (La_2O_3 and CeO_2) can refine and purify the microstructure, and can reduce the cracking susceptibility of coatings.
基金the National High-Tech Research and Development Program of China (No.2002AA305508)the National Natural Science Foundation of China (No.50472095)+1 种基金the Scientific Research Foundation for the Returned Overseas Chinese Scholars (No.2003-14)Beijing Novel Project (No. 2003A13).]
文摘Optical emission spectroscopy （OES） was used to study the gas phase composition near the substrate surface during diamond deposition by high-power DC arc plasma jet chemical vapor deposition （CVD）. C2 radical was determined as the main carbon radical in this plasma atmosphere. The deposition parameters, such as substrate temperature, anode-substrate distance, methane concentration, and gas flow rate, were inspected to find out the influence on the gas phase. A strong dependence of the concentrations and distribution of radicals on substrate temperature was confirmed by the design of experiments （DOE）. An explanation for this dependence could be that radicals near the substrate surface may have additional ionization or dissociation and also have recombination, or are consumed on the substrate surface where chemical reactions occur.
文摘The technical connotation of surface metallurgical technology by DC-Plasma-Jet is a kind of rapid, non- equilibrium metallurgical process which is similar to powder metallurgy. Accordingly the specialized equipment is developed all by ourselves, which is not subjected to limitation of solubility, melting point, density of constituents, therefore pre-alloy powders are not needed. The plasma surface metallurgical coating using Fe-Cr-C-Ni-B-Si mixed alloy powders has good wettability with substrate material. The metallurgical coating has apparent characteristics of rapid and layered crystallization from planar crystal-cell to dendritic transition zone at the interface, from dendritic crystal to equiaxed crystal in the midst, from equiaxed crystal to spike crystal on the surface. Its metastable microstructure is complex phase of supersaturated γ- （ Fe, Ni ） dendritic crystal solutioning great amount of alloy element and interdendritic eutectic structure （ Cr, Fe） γ （ C, B） 3 and T-（Fe,Ni）.
文摘DC plasma is a very promising technology for processing different materials, and is becoming especially interesting when low environmental impact and high-performance treatments are needed. Some of the intrinsic characteristics of DC plasma technology, which make it suitable for powder metallurgy （PM） and powder injection molding （PIM） parts production, are low- pressure processing and plasma environment high reactivity. Moreover it can be considered as a highly competitive green technology. In this work, an overview of some of the important DC plasma techniques applied to PM and PIM parts processing is presented. Emphasis is given to the descriptions of the main characteristics and the technique potentials of plasma-assisted nitriding, plasma-assisted thermal debinding, plasma-assisted sintering, and simultaneously plasma-assisted sintering and surface alloying. The aspects presented and discussed in this paper indicate that DC plasma processes are promising and competitive techniques for PM and PIM parts processing.
