The increasing complexity of modern functional materials leads to the demandof a cost efficient tool for the development of new products. One possible approach to this questionis the adaptation of combinatorial method...The increasing complexity of modern functional materials leads to the demandof a cost efficient tool for the development of new products. One possible approach to this questionis the adaptation of combinatorial methods to the specific requirements of materials industry.These methods, originally developed for the pharmaceutical industry, have recently been applied tothe screening of superconductive, magnetoresistant and photoluminescent materials. The principle ofthese combinatorial approaches is the deposition of large materials libraries in one processcombined with fast methods for the determination of the resulting properties. In this paper, thedeposition and characterization of laterally graded materials libraries (composition spread) ispresented. The films have been deposited by reactive magnetron sputtering, using two or threemetallic targets at a low angle to the substrate surface as well as a system of apertures. Toillustrate the advantages of combinatorial approaches for the development of advanced materials, themulticomponent metastable hardcoatings (Ti,Al)N and Ti-Al-Si-N are discussed with special emphasison the relations between structure and composition on the one hand and the oxidation resistance ofthese coatings on the other. The results illustrate that the composition spread approach is apowerful and cost efficient tool for the development and optimization of new multicomponentfunctional materials.展开更多
With the wide application of coating materials in aerospace and other fields, their safety under fatigue conditions in service is important.However, research on the fatigue properties of ceramic hard coatings started ...With the wide application of coating materials in aerospace and other fields, their safety under fatigue conditions in service is important.However, research on the fatigue properties of ceramic hard coatings started late, and a unified standard is yet to be established to evaluate the fatigue life of hard coating–ductile substrate systems.Studies also present different opinions on whether coatings can improve or reduce the fatigue life of substrates.In this paper, the influence of the properties of ceramic coatings on fatigue performance is reviewed, and the effects of coating on the mechanism of fatigue crack initiation in substrates are discussed, aiming to help readers understand the fatigue behavior of hard coating–ductile substrate systems.展开更多
TiN/CrN multilayered hard coatings with TiCrN interlayer were deposited onhigh speed steel substrates by using a filtered cathodic vacuum arc technique. The structure andcomposition of the coatings were characterized ...TiN/CrN multilayered hard coatings with TiCrN interlayer were deposited onhigh speed steel substrates by using a filtered cathodic vacuum arc technique. The structure andcomposition of the coatings were characterized by scanning electron microscopy (SEM) and Augerelectron spectroscopy (AES). A high adhesion of up to 80 N was demonstrated by scratching tests forthe multi-layered coatings. Nanoindentation tests were performed to determine the hardness andelastic modulus of the coatings as a function of the multiplayer modulation period. It was observedthat the hardness of the multilayered coatings is higher than those of either TiN or CrN singlecoatings, and it increases with decreasing modulation periods, which is consistent with predictionsfrom the Hall-Petch type strengthening mechanism, though at small modulation periods, deviation fromthe Hall-Petch relation has been observed for the multilayered coatings. The life-span of drillscoated with TiN/CrN multilayered is triple as long as that coated with TiN layer.展开更多
Most of materials used in applications that require high wear resistance also undergo corrosive action of the service environment. The damage caused by the combination of both processes on the materials leads to huge ...Most of materials used in applications that require high wear resistance also undergo corrosive action of the service environment. The damage caused by the combination of both processes on the materials leads to huge economic losses in industry. Hard coatings are widely used as engineering solution to increase the lifetime of components operating in conditions of wear combined with corrosion. Nowadays, the most versatile techniques for applying such coatings are welding and thermal spraying. This work evaluates and compares the properties of coatings obtained by thermal spraying and welding using selected feeding materials. The performance of the coatings in corrosion and erosive wear tests is discussed. From the erosion tests performed for impact angle of 90°, a similar performance for the thermally sprayed tungsten carbide coatings and the welded stainless steel coatings with higher input energy was observed. Welded samples presented the best performance in corrosion test.展开更多
Up-scaled deposition process of Teer-UDP850/4 has been established and used for massive production of CrTiAIN hard coatings in applications of anti-wear, cutting and forming tools. This deposition system uses four mag...Up-scaled deposition process of Teer-UDP850/4 has been established and used for massive production of CrTiAIN hard coatings in applications of anti-wear, cutting and forming tools. This deposition system uses four magnetrons that are arranged by unbalanced magnets to form closed magnetic field enabling the system running in high current density. Elemental metals of Cr, Ti and Al are used as the target materials which are co-deposited with nitrogen forming multialloy nitride, nanoscale multi-layer or superlattice hard coatings. The substrate turntable is desfgned as planet rotation mechanism with three folds so that components or tools with complicate geometry can be uniformly coated onto all their surfaces and cutting edges. The power units for the magnetrons are straight dc whilst the substrate is biased by pulsed dc. Two solid heaters are installed in the system to enable running a wide range of deposition temperature from 200°C to 500°C. The pumping system is powerful that incorporated with a polycold to pump the system to a good vacuum in a very short time. A front door and a movable substrate table are available to benefit easily loading and unloading. Deposition procedure, properties and performance of the coatings is also presented in this paper.展开更多
A structure of gradient hard coatings( Ti,TiN,TiCN and TiAlN) is designed,and residual stress is simulated by a finite element method with ANSYS. The influence of the realistic situation including load and temperature...A structure of gradient hard coatings( Ti,TiN,TiCN and TiAlN) is designed,and residual stress is simulated by a finite element method with ANSYS. The influence of the realistic situation including load and temperature on the residual stress of the coatings is investigated. Simulated results show that the realistic situation strongly affects the residual stress. To be specific,i) The main residual stress concentrates on the coatings prepared on YG8 substrate,and the residual stress and its gradient of the coatings are bigger than that of the substrate; ii) TiAlN and TiCN coatings have better resistance compression than that of TiN coatings in the same condition; iii) The improved multilayer structure of the gradient hard coatings produces weaker residual stress but higher anti-pressure of the substrate.展开更多
Arc Ion Plating can be used to synthesize multi-component composition gradient hard coatings by adjusting arc currents of metal targets. The present work aims at a comprehensive description of such a technique. The ex...Arc Ion Plating can be used to synthesize multi-component composition gradient hard coatings by adjusting arc currents of metal targets. The present work aims at a comprehensive description of such a technique. The examples of TiAl multi-layer alloy coatings and (Ti, M) N composition-gradient films were taken (M representing Zr, Nb etc.) for the purpose of explaining the working process and evaluating practical effects. The results show that this technique has the advantages of easy manipulation, rapid deposition, and wide composition range.展开更多
Using free bending method,the residual stress of the Ti(CN)coating on alloy Nb-752 was measured to be 2-3 GPa of which the thermal stress cmounts to 10—20%.An analysis on coating/substrate interface stress state show...Using free bending method,the residual stress of the Ti(CN)coating on alloy Nb-752 was measured to be 2-3 GPa of which the thermal stress cmounts to 10—20%.An analysis on coating/substrate interface stress state shows that the share stress at it is about O.1—0.2 GPa.The demage mode of the coating under external loading was proposed in terms of the amount and the direction of loading.展开更多
TiAlSiN hard coatings were synthesized on high-speed steel using an arc ion enhanced magnetic sputtering hybrid system.The microstructure and hardness of the coatings at different annealing temperatures were explored ...TiAlSiN hard coatings were synthesized on high-speed steel using an arc ion enhanced magnetic sputtering hybrid system.The microstructure and hardness of the coatings at different annealing temperatures were explored by means of XRD,TEM,EDAX and Vickers indentation.The as-deposited TiAlSiN coatings were confirmed to be amorphous due to high depositing rate and low deposition temperature during the film growth.The transformation from amorphous to nanocomposites of nano-crystallites and amorphousness were observed after the annealing treatment,the microstructure of TiAlSiN coatings annealed at 800°C and 1000°C were consisted of crystalline hcp-AlN,fcc-TiN and amorphous phase,however,the coatings were only consisted of fcc-TiN and amorphous phase when annealing at 1100°C and 1200°C.Meanwhile,the formation of Al2O3 was detected on the coating surface after annealing at 1200°C and it indicated the excellent oxidation resistance of the TiAlSiN coatings under the present experimental conditions.Furthermore,the average grain size of the TiAlSiN coatings after high temperature annealing even at 1200°C was less than 30 nm and the size increased with the increasing temperature.However,the hardness of the so-deposited coatings with HV0.2N=3300 dramatically decreased with the increase of temperature and reached nearly to the hardness of TiN coatings with HV0.2N=2300.展开更多
Flow based Erosion e corrosion problems are very common in fluid handling equipments such as propellers, impellers, pumps in warships, submarine. Though there are many coating materials available to combat erosionecor...Flow based Erosion e corrosion problems are very common in fluid handling equipments such as propellers, impellers, pumps in warships, submarine. Though there are many coating materials available to combat erosionecorrosion damage in the above components, iron based amorphous coatings are considered to be more effective to combat erosionecorrosion problems. High velocity oxy-fuel(HVOF)spray process is considered to be a better process to coat the iron based amorphous powders. In this investigation, iron based amorphous metallic coating was developed on 316 stainless steel substrate using HVOF spray technique. Empirical relationships were developed to predict the porosity and micro hardness of iron based amorphous coating incorporating HVOF spray parameters such as oxygen flow rate, fuel flow rate, powder feed rate, carrier gas flow rate, and spray distance. Response surface methodology(RSM) was used to identify the optimal HVOF spray parameters to attain coating with minimum porosity and maximum hardness.展开更多
The hardness, toughness and electrochemical properties of the CrN coatings were studied by the method of Ion Beam Enhanced DePosition(IBED). The results show that the fraction of CrN phase and its hardness increase wi...The hardness, toughness and electrochemical properties of the CrN coatings were studied by the method of Ion Beam Enhanced DePosition(IBED). The results show that the fraction of CrN phase and its hardness increase with increasing N2 partial pressure and N ions bombarding energy in a certain range, but the toughness decreases. When the N ions: Cr atoms ratio changes from 1. 45 × 1O-2, 3. 67 × 10-2 to 5. 87 ×10 - 2, Cr2O3 is produced. In terms of corrosion resistance, the coated specimen shows a slight improvement in comparison with substrate 52100 steel. The Cr-N coated specimen is characterized with pitting corrosion by penetrating the agent throngh the defects involved very thin coating layer.展开更多
Super-hard nanocomposite coatings have been received a great attention during recent years. Based on our previous investigations onto the several super-hard nanocomposite coating systems including nc-TiN/a-Si3N4, nc-T...Super-hard nanocomposite coatings have been received a great attention during recent years. Based on our previous investigations onto the several super-hard nanocomposite coating systems including nc-TiN/a-Si3N4, nc-TiN/a-BN. This paper reports on the nc-(Ti1.xAlxN)/a-Si3N4 nanocomposite coatings prepared by direct current plasma enhanced chemical vapor deposition (PECVD). And the effect of aluminum contents on the microstructure and hardness of the coatings have been mainly investigated. The coatings were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) equipped with energy dispersive analysis of X-rays (EDX), and the hardness measurements were done by means of the automated load-depth sensing technique using Vickers diamond indenter. The thermal stability of nanocomposite coatings of TiN/a-Si3N4 was evaluated by annealing at elevated temperatures up to 1000°C. The results shows that super hardness of nc-(Ti|_xAlxN)/a-Si3N4 could be obtained with a wide aluminum content from 10at.% to 86at.% in (Ti^AlJN phase, while the silicon content can be kept at 4-5 at.%. These nanocomposite coatings shows a relatively better thermal stability of nanocrystallite size and therefore high hardness up to 1000°C, which further support our earlier concept for the design of super-hard nanocomposite coatings. These results are suggested mainly due to the formation of nanostructure, and this indicates that the aluminum has also the role of controlling the crystallite size within nc-(Ti1.xAlIN)/a-Si3N4 besides its known well property of the super anti-oxidation.展开更多
In order to design the best combination of the coating and the substrate for preventing the yield,the semi-analytical method(SAM)was used to analyze the von Mises stress distributions in the contact system,and calcula...In order to design the best combination of the coating and the substrate for preventing the yield,the semi-analytical method(SAM)was used to analyze the von Mises stress distributions in the contact system,and calculate the critical maximum contact pressure for yielding at the interface and surface in hard coating under both normal and tangential loads on three-dimensional elastic half space.From the results,it can be concluded that,to obtain a higher maximum critical contact pressure for the yield at the interface,increasing the substrate hardness and the ratio value of the coating thickness to the Hertzian contact radius(t/a0)is more effective when t/a0 is larger than 0.5 while increasing the substrate hardness or making the friction coefficient smaller is better when t/a0 is very small;to prevent yielding at the surface,choosing a relatively lower friction system or increasing the yield strength ratio of the coating to the substrate(Yf/Yb)will be effective.展开更多
A coating with high hardness, wear and oxidation resistance was prepared by electric arc spray. The hardness, bonding strength, abrasive wear and values of porosity and oxidation resistance of the coating were investi...A coating with high hardness, wear and oxidation resistance was prepared by electric arc spray. The hardness, bonding strength, abrasive wear and values of porosity and oxidation resistance of the coating were investigated. The microstructures and function of Cr3C2 of the coating were analyzed. The results showed surface Rockness Hardness HR30 reached 72.5 and average bond strength reached 49.1Mpa. Also porosity value was less than 2%. In addition, it was found from the comparison between the coating and 45CT coating that, oxidation resistance of the coating was less than that of 45CT, but the abrasive wear of the coating was obvious better than that of 45CT.展开更多
The electroless Ni-P-SiC composite coatings were prepared and the influence of vacuum heat treatment on its structure and properties was analyzed. The Ni-P-SiC composite coatings were characterized by morphology,struc...The electroless Ni-P-SiC composite coatings were prepared and the influence of vacuum heat treatment on its structure and properties was analyzed. The Ni-P-SiC composite coatings were characterized by morphology,structure and micro-hardness. The morphology and structure of the Ni-P-SiC composite coatings were studied by scanning electron microscopy(SEM) and X-ray diffractometry(XRD),respectively. A great deal of particles incorporation and uniform distribution were found in Ni-P-SiC composite coatings. XRD results show a broad peak of nickel and low intensity SiC peaks present on as-deposited condition. Micro-hardness of as-deposited Ni-P-SiC composite coatings is improved greatly,and the best micro-hardness is obtained after heat treatment in a high vacuum at 400 ℃ .展开更多
基金The financial support is granted by the Deutsche Forschungsgemeinschaft, Collabo-rative Research Center 289. "Forming of metals in the semi solid state and their properties" is gratefully acknowledged.
文摘The increasing complexity of modern functional materials leads to the demandof a cost efficient tool for the development of new products. One possible approach to this questionis the adaptation of combinatorial methods to the specific requirements of materials industry.These methods, originally developed for the pharmaceutical industry, have recently been applied tothe screening of superconductive, magnetoresistant and photoluminescent materials. The principle ofthese combinatorial approaches is the deposition of large materials libraries in one processcombined with fast methods for the determination of the resulting properties. In this paper, thedeposition and characterization of laterally graded materials libraries (composition spread) ispresented. The films have been deposited by reactive magnetron sputtering, using two or threemetallic targets at a low angle to the substrate surface as well as a system of apertures. Toillustrate the advantages of combinatorial approaches for the development of advanced materials, themulticomponent metastable hardcoatings (Ti,Al)N and Ti-Al-Si-N are discussed with special emphasison the relations between structure and composition on the one hand and the oxidation resistance ofthese coatings on the other. The results illustrate that the composition spread approach is apowerful and cost efficient tool for the development and optimization of new multicomponentfunctional materials.
基金financially supported by the National Natural Science Foundation of China (Nos.51922002 and 51771025)the Fundamental Research Funds for the Central Universities (No.FRF-TP-17-19-003C1Z)。
文摘With the wide application of coating materials in aerospace and other fields, their safety under fatigue conditions in service is important.However, research on the fatigue properties of ceramic hard coatings started late, and a unified standard is yet to be established to evaluate the fatigue life of hard coating–ductile substrate systems.Studies also present different opinions on whether coatings can improve or reduce the fatigue life of substrates.In this paper, the influence of the properties of ceramic coatings on fatigue performance is reviewed, and the effects of coating on the mechanism of fatigue crack initiation in substrates are discussed, aiming to help readers understand the fatigue behavior of hard coating–ductile substrate systems.
基金This work was financially supported by the Science Foundation of Lanzhou Institute Chemistry and Physics, Chinese Academy of Science (No.01-03).
文摘TiN/CrN multilayered hard coatings with TiCrN interlayer were deposited onhigh speed steel substrates by using a filtered cathodic vacuum arc technique. The structure andcomposition of the coatings were characterized by scanning electron microscopy (SEM) and Augerelectron spectroscopy (AES). A high adhesion of up to 80 N was demonstrated by scratching tests forthe multi-layered coatings. Nanoindentation tests were performed to determine the hardness andelastic modulus of the coatings as a function of the multiplayer modulation period. It was observedthat the hardness of the multilayered coatings is higher than those of either TiN or CrN singlecoatings, and it increases with decreasing modulation periods, which is consistent with predictionsfrom the Hall-Petch type strengthening mechanism, though at small modulation periods, deviation fromthe Hall-Petch relation has been observed for the multilayered coatings. The life-span of drillscoated with TiN/CrN multilayered is triple as long as that coated with TiN layer.
文摘Most of materials used in applications that require high wear resistance also undergo corrosive action of the service environment. The damage caused by the combination of both processes on the materials leads to huge economic losses in industry. Hard coatings are widely used as engineering solution to increase the lifetime of components operating in conditions of wear combined with corrosion. Nowadays, the most versatile techniques for applying such coatings are welding and thermal spraying. This work evaluates and compares the properties of coatings obtained by thermal spraying and welding using selected feeding materials. The performance of the coatings in corrosion and erosive wear tests is discussed. From the erosion tests performed for impact angle of 90°, a similar performance for the thermally sprayed tungsten carbide coatings and the welded stainless steel coatings with higher input energy was observed. Welded samples presented the best performance in corrosion test.
文摘Up-scaled deposition process of Teer-UDP850/4 has been established and used for massive production of CrTiAIN hard coatings in applications of anti-wear, cutting and forming tools. This deposition system uses four magnetrons that are arranged by unbalanced magnets to form closed magnetic field enabling the system running in high current density. Elemental metals of Cr, Ti and Al are used as the target materials which are co-deposited with nitrogen forming multialloy nitride, nanoscale multi-layer or superlattice hard coatings. The substrate turntable is desfgned as planet rotation mechanism with three folds so that components or tools with complicate geometry can be uniformly coated onto all their surfaces and cutting edges. The power units for the magnetrons are straight dc whilst the substrate is biased by pulsed dc. Two solid heaters are installed in the system to enable running a wide range of deposition temperature from 200°C to 500°C. The pumping system is powerful that incorporated with a polycold to pump the system to a good vacuum in a very short time. A front door and a movable substrate table are available to benefit easily loading and unloading. Deposition procedure, properties and performance of the coatings is also presented in this paper.
基金Supported by the National High Technology Research and Development Programme of China(No.2012AA09A203)Project of Sichuan Education Department(No.14ZA0321)
文摘A structure of gradient hard coatings( Ti,TiN,TiCN and TiAlN) is designed,and residual stress is simulated by a finite element method with ANSYS. The influence of the realistic situation including load and temperature on the residual stress of the coatings is investigated. Simulated results show that the realistic situation strongly affects the residual stress. To be specific,i) The main residual stress concentrates on the coatings prepared on YG8 substrate,and the residual stress and its gradient of the coatings are bigger than that of the substrate; ii) TiAlN and TiCN coatings have better resistance compression than that of TiN coatings in the same condition; iii) The improved multilayer structure of the gradient hard coatings produces weaker residual stress but higher anti-pressure of the substrate.
文摘Arc Ion Plating can be used to synthesize multi-component composition gradient hard coatings by adjusting arc currents of metal targets. The present work aims at a comprehensive description of such a technique. The examples of TiAl multi-layer alloy coatings and (Ti, M) N composition-gradient films were taken (M representing Zr, Nb etc.) for the purpose of explaining the working process and evaluating practical effects. The results show that this technique has the advantages of easy manipulation, rapid deposition, and wide composition range.
文摘Using free bending method,the residual stress of the Ti(CN)coating on alloy Nb-752 was measured to be 2-3 GPa of which the thermal stress cmounts to 10—20%.An analysis on coating/substrate interface stress state shows that the share stress at it is about O.1—0.2 GPa.The demage mode of the coating under external loading was proposed in terms of the amount and the direction of loading.
基金supported by the National Natural Science Foundation of China (50671079, 50531060)National Basic Research Program of China (2004CB619302)Program for New Century Excellent Talents in University of China (NCET-04-0934)
文摘TiAlSiN hard coatings were synthesized on high-speed steel using an arc ion enhanced magnetic sputtering hybrid system.The microstructure and hardness of the coatings at different annealing temperatures were explored by means of XRD,TEM,EDAX and Vickers indentation.The as-deposited TiAlSiN coatings were confirmed to be amorphous due to high depositing rate and low deposition temperature during the film growth.The transformation from amorphous to nanocomposites of nano-crystallites and amorphousness were observed after the annealing treatment,the microstructure of TiAlSiN coatings annealed at 800°C and 1000°C were consisted of crystalline hcp-AlN,fcc-TiN and amorphous phase,however,the coatings were only consisted of fcc-TiN and amorphous phase when annealing at 1100°C and 1200°C.Meanwhile,the formation of Al2O3 was detected on the coating surface after annealing at 1200°C and it indicated the excellent oxidation resistance of the TiAlSiN coatings under the present experimental conditions.Furthermore,the average grain size of the TiAlSiN coatings after high temperature annealing even at 1200°C was less than 30 nm and the size increased with the increasing temperature.However,the hardness of the so-deposited coatings with HV0.2N=3300 dramatically decreased with the increase of temperature and reached nearly to the hardness of TiN coatings with HV0.2N=2300.
文摘Flow based Erosion e corrosion problems are very common in fluid handling equipments such as propellers, impellers, pumps in warships, submarine. Though there are many coating materials available to combat erosionecorrosion damage in the above components, iron based amorphous coatings are considered to be more effective to combat erosionecorrosion problems. High velocity oxy-fuel(HVOF)spray process is considered to be a better process to coat the iron based amorphous powders. In this investigation, iron based amorphous metallic coating was developed on 316 stainless steel substrate using HVOF spray technique. Empirical relationships were developed to predict the porosity and micro hardness of iron based amorphous coating incorporating HVOF spray parameters such as oxygen flow rate, fuel flow rate, powder feed rate, carrier gas flow rate, and spray distance. Response surface methodology(RSM) was used to identify the optimal HVOF spray parameters to attain coating with minimum porosity and maximum hardness.
文摘The hardness, toughness and electrochemical properties of the CrN coatings were studied by the method of Ion Beam Enhanced DePosition(IBED). The results show that the fraction of CrN phase and its hardness increase with increasing N2 partial pressure and N ions bombarding energy in a certain range, but the toughness decreases. When the N ions: Cr atoms ratio changes from 1. 45 × 1O-2, 3. 67 × 10-2 to 5. 87 ×10 - 2, Cr2O3 is produced. In terms of corrosion resistance, the coated specimen shows a slight improvement in comparison with substrate 52100 steel. The Cr-N coated specimen is characterized with pitting corrosion by penetrating the agent throngh the defects involved very thin coating layer.
基金supports of National High-Tech ProgramNational Natural Science Foundation of China are greatly acknowledged under grant number 2001AA338010,50271053 and 50371067.
文摘Super-hard nanocomposite coatings have been received a great attention during recent years. Based on our previous investigations onto the several super-hard nanocomposite coating systems including nc-TiN/a-Si3N4, nc-TiN/a-BN. This paper reports on the nc-(Ti1.xAlxN)/a-Si3N4 nanocomposite coatings prepared by direct current plasma enhanced chemical vapor deposition (PECVD). And the effect of aluminum contents on the microstructure and hardness of the coatings have been mainly investigated. The coatings were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) equipped with energy dispersive analysis of X-rays (EDX), and the hardness measurements were done by means of the automated load-depth sensing technique using Vickers diamond indenter. The thermal stability of nanocomposite coatings of TiN/a-Si3N4 was evaluated by annealing at elevated temperatures up to 1000°C. The results shows that super hardness of nc-(Ti|_xAlxN)/a-Si3N4 could be obtained with a wide aluminum content from 10at.% to 86at.% in (Ti^AlJN phase, while the silicon content can be kept at 4-5 at.%. These nanocomposite coatings shows a relatively better thermal stability of nanocrystallite size and therefore high hardness up to 1000°C, which further support our earlier concept for the design of super-hard nanocomposite coatings. These results are suggested mainly due to the formation of nanostructure, and this indicates that the aluminum has also the role of controlling the crystallite size within nc-(Ti1.xAlIN)/a-Si3N4 besides its known well property of the super anti-oxidation.
基金NSFC(90923027 and 51050110137)Fundamental Research Funds for Central Universities
文摘In order to design the best combination of the coating and the substrate for preventing the yield,the semi-analytical method(SAM)was used to analyze the von Mises stress distributions in the contact system,and calculate the critical maximum contact pressure for yielding at the interface and surface in hard coating under both normal and tangential loads on three-dimensional elastic half space.From the results,it can be concluded that,to obtain a higher maximum critical contact pressure for the yield at the interface,increasing the substrate hardness and the ratio value of the coating thickness to the Hertzian contact radius(t/a0)is more effective when t/a0 is larger than 0.5 while increasing the substrate hardness or making the friction coefficient smaller is better when t/a0 is very small;to prevent yielding at the surface,choosing a relatively lower friction system or increasing the yield strength ratio of the coating to the substrate(Yf/Yb)will be effective.
基金sponsored by National Natural Science Foundation of China(50375004).
文摘A coating with high hardness, wear and oxidation resistance was prepared by electric arc spray. The hardness, bonding strength, abrasive wear and values of porosity and oxidation resistance of the coating were investigated. The microstructures and function of Cr3C2 of the coating were analyzed. The results showed surface Rockness Hardness HR30 reached 72.5 and average bond strength reached 49.1Mpa. Also porosity value was less than 2%. In addition, it was found from the comparison between the coating and 45CT coating that, oxidation resistance of the coating was less than that of 45CT, but the abrasive wear of the coating was obvious better than that of 45CT.
基金Projects(05B008) supported by Scientific Research Fund of Hunan Provincial Education Departmentproject(104014) supported by Fok Ying Tong Education Foundation of Ministry of Education
文摘The electroless Ni-P-SiC composite coatings were prepared and the influence of vacuum heat treatment on its structure and properties was analyzed. The Ni-P-SiC composite coatings were characterized by morphology,structure and micro-hardness. The morphology and structure of the Ni-P-SiC composite coatings were studied by scanning electron microscopy(SEM) and X-ray diffractometry(XRD),respectively. A great deal of particles incorporation and uniform distribution were found in Ni-P-SiC composite coatings. XRD results show a broad peak of nickel and low intensity SiC peaks present on as-deposited condition. Micro-hardness of as-deposited Ni-P-SiC composite coatings is improved greatly,and the best micro-hardness is obtained after heat treatment in a high vacuum at 400 ℃ .