This paper describes a new method of surface modification by Electrical Discharge Machining (EDM). By using ordinary EDM machine tool and kerosene fluid, a hard ceramic layer can be created on the workpiece surface wi...This paper describes a new method of surface modification by Electrical Discharge Machining (EDM). By using ordinary EDM machine tool and kerosene fluid, a hard ceramic layer can be created on the workpiece surface with Ti or other compressed powder electrode in a certain condition. This new revolutionary method is called Electrical Discharge Coating (EDC). The process of EDC begins with electrode wear during EDM,then a kind of hard carbide is created through the thermal and chemical reaction between the worn electrode material and the carbon particle decomposed from kerosene fluid under high temperature. The carbide is piled up on a workpiece quickly and becomes a hard layer of ceramic about 20 μm in several minutes. This paper studies the principle and process of EDC systemically by using Ti powder green compact electrode. In order to obtain a layer of compact ceramic film, it is very important to select proper electric pulse parameters, such as pulse width, pulse interval, peak current. Meantime, the electrode materials and its forming mode will effect the machining surface quality greatly. This paper presents a series of experiment results to study the EDC process by adopt different technology parameters. Experiments and analyses show that a compact TiC ceramic layer can be created on the surface of metal workpiece. The hardness of ceramic layer is more 3 times higher than the base body, and the hardness changes gradiently from surface to base body. The method will have a great future because many materials can be easily added to the electrode and then be coated on the workpiece surface. Gearing the parameters ceramic can be created with different thickness. The switch between deposition and removal process is carried out easily by changing the polarity, thus the gear to the thickness and shape of the composite ceramic layer is carried out easily. This kind of composite ceramic layer will be used to deal with the surface of the cutting tools or molds possibly, in order to lengthen their life. It also can be found wide application in the fields of surface repairing and strengthening of the ship or aircraft.展开更多
Using Ti powder as reagent, TiO 2 nanoneedle/nanoribbon spheres were prepared via hydrothermal method in NaOH solution. The samples were characterized by field emission scanning electron microscopy （FESEM）, transmis...Using Ti powder as reagent, TiO 2 nanoneedle/nanoribbon spheres were prepared via hydrothermal method in NaOH solution. The samples were characterized by field emission scanning electron microscopy （FESEM）, transmission electron microscopy （TEM） with selected area electron diffraction （SAED）, X-ray diffraction （XRD）, and UV-visible light absorption spectrum. The results indicate that the growth orientations of the crystals are influenced by the hydrothermal temperature and NaOH concentration. The diameter of the nanoneedle spheres and nanoribbon spheres （40 50 μm） are almost the same as that of Ti powders. TiO 2 nanoneedle/nanoribbon sphere powders are anatase after heat treatment at 450 °C for 1 h. Furthermore, methyl orange was used as a target molecule to estimate the photocatalytic activity of the specimens. Under the same testing conditions, the photocatalytic activities of the products decrease in the following order： TiO 2 nanoneedle sphere, TiO 2 nanoribbon sphere and P25.展开更多
After milling in a high energy ball miller for various times, the synthesis reaction process of the Al Ti C powder mixture were investigated by difference thermal analysis (DTA) and X ray diffractometry (XRD). Accordi...After milling in a high energy ball miller for various times, the synthesis reaction process of the Al Ti C powder mixture were investigated by difference thermal analysis (DTA) and X ray diffractometry (XRD). According to the patterns of reaction peaks on the DTA curves, the activation energy of each reaction was calculated. The experimental results of DTA show that the synthesis reaction of Al Ti C powder mixture can be enhanced after high energy milling. The longer the milling time, the lower the reaction temperature. The synthesis reaction of TiC is transformed from Ti+C→TiC to Al 3Ti+C→TiC+3Al with long period milling. Meanwhile, the activation energy of the reaction reduces with increasing milling time. The effect of milling time on reduced activation energy for low temperature region is more significant than that for high temperature region.展开更多
The effects of preheating temperature and W powder size on the Self propagating High temperature Synthesis(SHS) of Ti W C system were studied. Preheated mixtures and the decrease of W powder size can accelerate the fo...The effects of preheating temperature and W powder size on the Self propagating High temperature Synthesis(SHS) of Ti W C system were studied. Preheated mixtures and the decrease of W powder size can accelerate the formation of (W,Ti)C powders. The uniphase (W,Ti)C (WC∶TiC=5∶5) powders with 0.32% free carbon were synthesized from Ti, W, C powders by SHS. The powder size of the product was 3～5 μm.展开更多
This study was carried out to investigate the possibility of titanium alloy metal powder production using low-power plasma torches.An argon DC non-transferred arc plasma torch was designed,and numerical analysis was c...This study was carried out to investigate the possibility of titanium alloy metal powder production using low-power plasma torches.An argon DC non-transferred arc plasma torch was designed,and numerical analysis was conducted to determine the plasma jet properties and wire temperature.The highest velocities inside the nozzle attachment were between 838 and 1178 m/s.The velocities of the jets at the apex were between 494 and 645 m/s for different gas flow rates.The studied plasma gas flow rates had no significant effect on the effective plasma jet length.It was shown that the plasma jet length can be estimated by numerical analysis using the temperature and velocity changes of the plasma jet over distance.It was observed that the powders produced were spherical without any satellites.As a result of this study,a plasma torch was developed and powder production was performed successfully by using relatively low torch power.展开更多
Taking Ti6Al4V titanium alloy powder as the research object,on the basis of single layer scanning and single channel scanning experiment,this paper studies the influence of selective laser melting(SLM)process paramete...Taking Ti6Al4V titanium alloy powder as the research object,on the basis of single layer scanning and single channel scanning experiment,this paper studies the influence of selective laser melting(SLM)process parameters on Ti6Al4V alloy material formability,and block forming experiment is carried out.Through the design of orthogonal experiment,morphology observation of sample and density analysis,results show that the best block molding parameters of SLM technology in Ti6Al4V alloy powder are laser power of 400 W,lap rate of 1 and the scanning speed of 750 mm/min,density can up to 96.17%.展开更多
The properties and forming process of prealloyed powder metallurgy(PM) Ti-6Al-4V alloy were researched for application of high performance of titanium parts. Hot isostatic press(HIP) technology and two kinds of powder...The properties and forming process of prealloyed powder metallurgy(PM) Ti-6Al-4V alloy were researched for application of high performance of titanium parts. Hot isostatic press(HIP) technology and two kinds of powders were used in the prealloyed processing to get full density material. Tensile properties,impact toughness and fracture toughness of PM Ti-6Al-4V alloy were studied and discussed. The microstructures were examined with optical microscope and the morphologies of powders were observed by SEM. Forming processes were performed to fabricate PM titanium parts. The experiment results show that the prealloyed PM Ti-6Al-4V alloy has same good properties as wrought material and the complex shape PM parts can be near-net-shaped. Some of the parts have been commercially used. This indicates that the prealloyed process should have bright prospects in making high-performance,complex shape and low-cost titanium alloy parts.展开更多
The influence of raw powder particle size on the properties and microstructures of Ti (C, N)-based cermets has been studied. The conclusions are as follows: The microstructures of cermets were composed of two kinds of...The influence of raw powder particle size on the properties and microstructures of Ti (C, N)-based cermets has been studied. The conclusions are as follows: The microstructures of cermets were composed of two kinds of grains, the one with black cores surrounded by obvious rim structures, and the other whose cores were white with unconspicuous rim structures and adhesive phase. In the cermet made from fine powders, the amount of grains with white cores was much more than that in cermet made from coarse powders. In addition, their properties were also much better.展开更多
Ti6Al4V powder compaction was performed by using magnetic pulse compaction in air at 200℃.Effects of process parameters such as voltage,capacitance,discharge times on the microstructure,compressive strength,hardness ...Ti6Al4V powder compaction was performed by using magnetic pulse compaction in air at 200℃.Effects of process parameters such as voltage,capacitance,discharge times on the microstructure,compressive strength,hardness and relative density of compacts were investigated.The experimental results show that the relative density,hardness and compressive strength of compacted specimens increase with increasing voltage.In addition,the relative density and compressive strength of compacted specimens increase with the augmentation of capacitance in the range investigated.The relative density increases,the hardness firstly increases and then tends to be a fixed value;and the compressive strength firstly increases and then decreases from one to five times compaction.Both values of the hardness and compressive strength reach the maxima of HRA 69.1 and 1 062.31 MPa,at three times compaction,respectively.There are pores in and between particles.展开更多
CNTs/TiH2 composite powders were prepared by plasma enhanced chemical vapor deposition （PECVD）. CNTs dispersed uniformly on the surface of Till2 particles and few defects were found in the tubular structure of the C...CNTs/TiH2 composite powders were prepared by plasma enhanced chemical vapor deposition （PECVD）. CNTs dispersed uniformly on the surface of Till2 particles and few defects were found in the tubular structure of the CNTs. According to DTA analysis, CNTs do not react with the base material Ti under 1 200 ~C. In order to investigate the application of CNTs/ Till2 powders in brazing, CNTs/TiH2 powders were mechanically mixed with Ni powders to develop a new type of brazing powder, and wetting experiments at 1 100 ~C showed a good wettability of CNTs/TiNi brazing powder.展开更多
文摘This paper describes a new method of surface modification by Electrical Discharge Machining (EDM). By using ordinary EDM machine tool and kerosene fluid, a hard ceramic layer can be created on the workpiece surface with Ti or other compressed powder electrode in a certain condition. This new revolutionary method is called Electrical Discharge Coating (EDC). The process of EDC begins with electrode wear during EDM,then a kind of hard carbide is created through the thermal and chemical reaction between the worn electrode material and the carbon particle decomposed from kerosene fluid under high temperature. The carbide is piled up on a workpiece quickly and becomes a hard layer of ceramic about 20 μm in several minutes. This paper studies the principle and process of EDC systemically by using Ti powder green compact electrode. In order to obtain a layer of compact ceramic film, it is very important to select proper electric pulse parameters, such as pulse width, pulse interval, peak current. Meantime, the electrode materials and its forming mode will effect the machining surface quality greatly. This paper presents a series of experiment results to study the EDC process by adopt different technology parameters. Experiments and analyses show that a compact TiC ceramic layer can be created on the surface of metal workpiece. The hardness of ceramic layer is more 3 times higher than the base body, and the hardness changes gradiently from surface to base body. The method will have a great future because many materials can be easily added to the electrode and then be coated on the workpiece surface. Gearing the parameters ceramic can be created with different thickness. The switch between deposition and removal process is carried out easily by changing the polarity, thus the gear to the thickness and shape of the composite ceramic layer is carried out easily. This kind of composite ceramic layer will be used to deal with the surface of the cutting tools or molds possibly, in order to lengthen their life. It also can be found wide application in the fields of surface repairing and strengthening of the ship or aircraft.
基金Project (NS2010153) supported by Nanjing University of Aeronautics and Astronautics Research Funding, ChinaProject (BE2009130) supported by Jiangsu Key Technology R&D Program, China
文摘Using Ti powder as reagent, TiO 2 nanoneedle/nanoribbon spheres were prepared via hydrothermal method in NaOH solution. The samples were characterized by field emission scanning electron microscopy （FESEM）, transmission electron microscopy （TEM） with selected area electron diffraction （SAED）, X-ray diffraction （XRD）, and UV-visible light absorption spectrum. The results indicate that the growth orientations of the crystals are influenced by the hydrothermal temperature and NaOH concentration. The diameter of the nanoneedle spheres and nanoribbon spheres （40 50 μm） are almost the same as that of Ti powders. TiO 2 nanoneedle/nanoribbon sphere powders are anatase after heat treatment at 450 °C for 1 h. Furthermore, methyl orange was used as a target molecule to estimate the photocatalytic activity of the specimens. Under the same testing conditions, the photocatalytic activities of the products decrease in the following order： TiO 2 nanoneedle sphere, TiO 2 nanoribbon sphere and P25.
文摘After milling in a high energy ball miller for various times, the synthesis reaction process of the Al Ti C powder mixture were investigated by difference thermal analysis (DTA) and X ray diffractometry (XRD). According to the patterns of reaction peaks on the DTA curves, the activation energy of each reaction was calculated. The experimental results of DTA show that the synthesis reaction of Al Ti C powder mixture can be enhanced after high energy milling. The longer the milling time, the lower the reaction temperature. The synthesis reaction of TiC is transformed from Ti+C→TiC to Al 3Ti+C→TiC+3Al with long period milling. Meanwhile, the activation energy of the reaction reduces with increasing milling time. The effect of milling time on reduced activation energy for low temperature region is more significant than that for high temperature region.
文摘The effects of preheating temperature and W powder size on the Self propagating High temperature Synthesis(SHS) of Ti W C system were studied. Preheated mixtures and the decrease of W powder size can accelerate the formation of (W,Ti)C powders. The uniphase (W,Ti)C (WC∶TiC=5∶5) powders with 0.32% free carbon were synthesized from Ti, W, C powders by SHS. The powder size of the product was 3～5 μm.
基金financial supports from the Scientific and Technological Research Council of Turkey(No.215M895)。
文摘This study was carried out to investigate the possibility of titanium alloy metal powder production using low-power plasma torches.An argon DC non-transferred arc plasma torch was designed,and numerical analysis was conducted to determine the plasma jet properties and wire temperature.The highest velocities inside the nozzle attachment were between 838 and 1178 m/s.The velocities of the jets at the apex were between 494 and 645 m/s for different gas flow rates.The studied plasma gas flow rates had no significant effect on the effective plasma jet length.It was shown that the plasma jet length can be estimated by numerical analysis using the temperature and velocity changes of the plasma jet over distance.It was observed that the powders produced were spherical without any satellites.As a result of this study,a plasma torch was developed and powder production was performed successfully by using relatively low torch power.
文摘Taking Ti6Al4V titanium alloy powder as the research object,on the basis of single layer scanning and single channel scanning experiment,this paper studies the influence of selective laser melting(SLM)process parameters on Ti6Al4V alloy material formability,and block forming experiment is carried out.Through the design of orthogonal experiment,morphology observation of sample and density analysis,results show that the best block molding parameters of SLM technology in Ti6Al4V alloy powder are laser power of 400 W,lap rate of 1 and the scanning speed of 750 mm/min,density can up to 96.17%.
文摘The properties and forming process of prealloyed powder metallurgy(PM) Ti-6Al-4V alloy were researched for application of high performance of titanium parts. Hot isostatic press(HIP) technology and two kinds of powders were used in the prealloyed processing to get full density material. Tensile properties,impact toughness and fracture toughness of PM Ti-6Al-4V alloy were studied and discussed. The microstructures were examined with optical microscope and the morphologies of powders were observed by SEM. Forming processes were performed to fabricate PM titanium parts. The experiment results show that the prealloyed PM Ti-6Al-4V alloy has same good properties as wrought material and the complex shape PM parts can be near-net-shaped. Some of the parts have been commercially used. This indicates that the prealloyed process should have bright prospects in making high-performance,complex shape and low-cost titanium alloy parts.
基金the National Natural Science Foundation of China, the Doctoral EducationFoundation of China, the State Key Laboratory of Powde
文摘The influence of raw powder particle size on the properties and microstructures of Ti (C, N)-based cermets has been studied. The conclusions are as follows: The microstructures of cermets were composed of two kinds of grains, the one with black cores surrounded by obvious rim structures, and the other whose cores were white with unconspicuous rim structures and adhesive phase. In the cermet made from fine powders, the amount of grains with white cores was much more than that in cermet made from coarse powders. In addition, their properties were also much better.
文摘Ti6Al4V powder compaction was performed by using magnetic pulse compaction in air at 200℃.Effects of process parameters such as voltage,capacitance,discharge times on the microstructure,compressive strength,hardness and relative density of compacts were investigated.The experimental results show that the relative density,hardness and compressive strength of compacted specimens increase with increasing voltage.In addition,the relative density and compressive strength of compacted specimens increase with the augmentation of capacitance in the range investigated.The relative density increases,the hardness firstly increases and then tends to be a fixed value;and the compressive strength firstly increases and then decreases from one to five times compaction.Both values of the hardness and compressive strength reach the maxima of HRA 69.1 and 1 062.31 MPa,at three times compaction,respectively.There are pores in and between particles.
基金This work was supported by the National Natural Science Foundation of China （Grant No. 51105108 ） and the Fundamental Research Funds for the Central Universities （Grant No. HIT. NSRIF. 2010113）.
文摘CNTs/TiH2 composite powders were prepared by plasma enhanced chemical vapor deposition （PECVD）. CNTs dispersed uniformly on the surface of Till2 particles and few defects were found in the tubular structure of the CNTs. According to DTA analysis, CNTs do not react with the base material Ti under 1 200 ~C. In order to investigate the application of CNTs/ Till2 powders in brazing, CNTs/TiH2 powders were mechanically mixed with Ni powders to develop a new type of brazing powder, and wetting experiments at 1 100 ~C showed a good wettability of CNTs/TiNi brazing powder.
基金Project(LQ21E040004) supported by the Natural Science Foundation of Zhejiang Province,ChinaProject(2021-Z03) supported by the State Key Laboratory of Advanced Metals and Materials,China。
