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 microsmictures 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 microsmictures 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
The submicron powder mixtures of TiC-TiN-WC-Mo-C-Ni sintered at 1400℃ or below in vacuum were studied by X-ray diffration （XRD）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM） ana...The submicron powder mixtures of TiC-TiN-WC-Mo-C-Ni sintered at 1400℃ or below in vacuum were studied by X-ray diffration （XRD）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM） analyses. The results showed that Mo2C fOrmed at 800℃ or below. Both WC and Mo2C disappeared at 1200 ℃, and TiN disappeared at 1250℃. In addihon, the variahons of lanice constans of the htanium carbonitride and nickel binder phase with sintering temperature were experimentally obtained, and the reason was analyzed.展开更多
High temperature solid oxide fuel cell(SOFC)is the most efficient and clean energy conversion technology to electrochemically convert the chemical energy of fuels such as hydrogen,natural gas and hydrocarbons to elect...High temperature solid oxide fuel cell(SOFC)is the most efficient and clean energy conversion technology to electrochemically convert the chemical energy of fuels such as hydrogen,natural gas and hydrocarbons to electricity,and also the most viable alternative to the traditional thermal power plants.However,the power output of a SOFC critically depends on the characteristics and performance of its key components:anode,electrolyte and cathode.Due to the highly reducing environment and strict requirements in electrical conductivity and catalytic activity,there are limited choices in the anode materials of SOFCs,particularly for operation in the intermediate temperature range of 500–800C.Among them,Ni-based cermets are the most common and popular anode materials of SOFCs.The objective of this paper is to review the development of Ni-based anode materials in SOFC from the viewpoints of materials microstructure,performance and industrial scalability associated with the fabrication and optimization processes.The latest advancement in nano-structure architecture,contaminant tolerance and interface optimization of Ni-based cermet anodes is presented.And at the end of this paper,we propose and appeal for the collaborative work of scientists from different disciplines that enable the inter-fusion research of fabrication,microanalysis and modelling,aiming at the challenges in the development of Ni-based cermet anodes for commercially viable intermediate temperature SOFC or IT-SOFC technologies.展开更多
Ni-based anodes of SOFCs are susceptible to coking, which greatly limits practical application of direct methane-based fuels. An indirect internal reformer is an effective way to convert methane-based fuels into synga...Ni-based anodes of SOFCs are susceptible to coking, which greatly limits practical application of direct methane-based fuels. An indirect internal reformer is an effective way to convert methane-based fuels into syngas before they reach anode. In this work, catalytic activity of a redox-stable perovskite La0.7Sr0.3Cr0.8Fe0.2O3-δ(LSCrFO) for methane conversion was evaluated. The catalyst was fabricated as an anodic protective layer to improve coking resistance of a Ni cermet anode. Using wet CH4 as a fuel, the LSCrFO-modified cell showed excellent power output and good coking resistance with peak power density of 1.59 W cm-2 at 800℃. The cell demonstrated good durability lasting for at least 100 h. While the bare cell without the protective layer showed poor durability with the cell voltage fast dropped from 0.75 V to 0.4 V within 30 min. Under wet coal bed methane (CBM) operation, obvious performance degradation within 35 h (1.7 mV h^-1) was observed due to the influence of heavy carbon compounds in CBM. The pre-and post-mortem microstructures and carbon analysis of the anode surface and catalyst surface were further conducted.展开更多
The enriching of metals to the center of sample was found and investigated during the sinterprocess of the cermet.The enrichment is caused by addition with Y<sub>2</sub>O<sub>3</sub>.The enrich...The enriching of metals to the center of sample was found and investigated during the sinterprocess of the cermet.The enrichment is caused by addition with Y<sub>2</sub>O<sub>3</sub>.The enriching of copper is greatly in-fluenced by sinter temperature and time.The enriching of metal can significantly enhance the electrical con-ductivity of the cermet.展开更多
Ti(C,N)-TiB2 cermets were fabricated from Ti(C,N), TiB2, Co and WC powder mixtures via a vacuum hot pressing process. The influence of TiB2 content on their microstructures and mechanical properties was investigated. ...Ti(C,N)-TiB2 cermets were fabricated from Ti(C,N), TiB2, Co and WC powder mixtures via a vacuum hot pressing process. The influence of TiB2 content on their microstructures and mechanical properties was investigated. As a result of the elevated TiB2 contents, two types of corerim microstructures were present in the Ti(C,N)-TiB2 cermets, and remarkably improved mechanical properties were achieved. With the increase of TiB2 content, the flexural strength, fracture toughness and hardness of the Ti(C,N)-TiB2 cermets first increased, and then decreased, while their relative density consistently decreased. Attributed to an integration of the intergranular and intrangranular fracture behaviors, the Ti(C,N)-TiB2 cermets with 20 wt% TiB2 content exhibited the best overall properties with the relative density, hardness, fracture toughness and flexural strength at 99.3%, 1 995 HV, 7.92 MPa·m1/2 and 1 114 MPa, respectively. The underlying mechanism for their enhanced properties was studied in detail.展开更多
The dense TiC Fe cermets were produced by self propagating high temperature synthesis and pseudo hot isostatic pressing(SHS/PHIP). The influence of Fe content on the combustion temperature, combustion velocity, densit...The dense TiC Fe cermets were produced by self propagating high temperature synthesis and pseudo hot isostatic pressing(SHS/PHIP). The influence of Fe content on the combustion temperature, combustion velocity, density and microstructure of products was studied. The composition and microstructure of the product were analyzed. The results showed that the cermet consists of quasi spherical TiC particles and Fe binder phases. A thin diffusion layer was found between Fe binder phase and TiC particle. In the range of 10%～20% Fe content, the combustion temperature and velocity decrease more slowly than the other contributions.展开更多
TiAl alloys were joined to TiC cermets using combustion synthesis method. The Ti-C-Ni metallic powder compact acted as a joining interlayer in the joining process. The identification and mechanisms of the reaction at ...TiAl alloys were joined to TiC cermets using combustion synthesis method. The Ti-C-Ni metallic powder compact acted as a joining interlayer in the joining process. The identification and mechanisms of the reaction at the interface and interlayer were investigated. From the analysis of the microstructure of TiAl/TiC cermet joint, it is noted that TiC and TiNi compounds are main reaction products and unreacted Ni is observed in the interlayer. The reaction products consist of a large volume of voids or unreacted regions. It is confirmed that Al addition as well as joining pressure are effective to decrease the voids. It is considered that high flowability of liquid Al enhances the SHS reaction and the densification of reaction products. There is a continuous Ni-rich layer observed at the interface between the interlayer and TiC cermets substrate. Ti3Al, TiC and TiNi compounds are observed in the reaction products.展开更多
Stress concentration zones and the maximum value of thermal stress of TiC cermet/iron joint brazed with Ag-Cu-Zn filler metal during cooling were studied. The results show that when the temperature is 300K, the maxi...Stress concentration zones and the maximum value of thermal stress of TiC cermet/iron joint brazed with Ag-Cu-Zn filler metal during cooling were studied. The results show that when the temperature is 300K, the maximum values of shear stress and tensile stress on TiC cermet/iron interface both appear on the tip of Ag-Cu-Zn/iron interface, which makes Ag-Cu-Zn/iron interface become weak zone of the interface. Tensile stress on iron undersurface relaxes to the inner of iron, and the compression stress on iron undersurface concentrates on the side of iron as the temperature decreases, so cracks appear easily at the site where tensile and compression stress cross.展开更多
The variations of chemical compositions, phases, microstructure evolution and shrinking of cermets compact debinded in H2 or in vacuum and sintered subsequently in vacuum were studied systematically using chemical ana...The variations of chemical compositions, phases, microstructure evolution and shrinking of cermets compact debinded in H2 or in vacuum and sintered subsequently in vacuum were studied systematically using chemical analysis, back scattering scanning electron microscopy (SEM), and X-ray diffractometry (XRD). The total carbon of cermets debinded in H2 is lower than that debinded in vacuum by 0.4%-0.5%. The contents of carbon and oxygen are decreased sharply when being sintered at 1 100-1 300 ℃. The decomposition reaction of nitrogen is conducted sharply at 1 300 ℃. However, the decomposition of nitrogen is inhibited while the liquid phase appears, and then begins again above 1 500 ℃. The solution reaction of TaC and Mo2C into ring phase starts at 1 200 ℃, and WC into ring phase at 1 300 ℃ is finished. Therefore, the heating rate during sintering of cermets between 900 ℃ and 1 350 ℃ is important.展开更多
The microstructure and mechanical properties of Ti(C, N)-based cermets with different content Mo were studied. Different Mo contents were added into Ti(C, N)-based cermets. Effect of sintering temperature on mechanica...The microstructure and mechanical properties of Ti(C, N)-based cermets with different content Mo were studied. Different Mo contents were added into Ti(C, N)-based cermets. Effect of sintering temperature on mechanical properties of the cermets was also investigated. Specimens were fabricated by conventional powder metallurgy techniques and vacuum sintered at different temperatures. The microstructure and the fracture morphology were investigated using scanning electron microscope. Transverse strength and hardness were measured. The results show that the microstructure is uniform and the thickness of rim phase is moderate when the content of Mo is 8%. The mechanical properties are the best when the content of Mo is 8% and the sintering temperature is 1450℃.展开更多
Fe-Cr-C cermet was prepared by reaction sintering of ferrochromium and graphite. The exothermic reaction was determined by DTA. The effect of carbon content on the porosity, hardness and oxidation resistance was inves...Fe-Cr-C cermet was prepared by reaction sintering of ferrochromium and graphite. The exothermic reaction was determined by DTA. The effect of carbon content on the porosity, hardness and oxidation resistance was investigated. The result showed that the cermet with 6 %-7 % of carbon has high hardness and oxidation resistance.展开更多
Effect of two-stage sintering parameters such as heating rate, top sintering temperature and holding time, sintering temperature and holding time at the second stage on relative density, transverse rupture strength(TR...Effect of two-stage sintering parameters such as heating rate, top sintering temperature and holding time, sintering temperature and holding time at the second stage on relative density, transverse rupture strength(TRS) and microstructures of powder injection molded Ti(C, N)-based cermets were investigated, by means of Archimedes’s method, three-point bending test and micrographic analysis. The results show that the optimum sintering cycle for powder injection molded Ti(C, N)-based cermets comprises rapid heating (10℃/min) at low temperatures, slow heating (5℃/min) at intermediate temperatures, holding at the highest sintering temperature (1420℃) for a short time (10min), and holding at the second stage (1360℃) for a longer time (6h) to avoid grain coarsening, and that its TRS reaches 624MPa, and there are little pores in their microstructures.展开更多
Cu-Cu2O cermets were prepared via hot pressing（HP） or in situ reduction hot pressing （ISPHP）. The results of electric conductivity tests show that the percolation threshold of the cermet, which is prepared by HP, ...Cu-Cu2O cermets were prepared via hot pressing（HP） or in situ reduction hot pressing （ISPHP）. The results of electric conductivity tests show that the percolation threshold of the cermet, which is prepared by HP, is lower than that of cermet prepared by ISRHP. The electric conductivity and the percolation threshold depend on four influencing factors: the content, the size, the shape and the distribution of Cu phase. The electric conductivity decreases with the increase of Cu particle size, and decrease of the aspect ratio of Cu particle. The more even the Cu phase distribution, the higher the electric conductivity of the cermets.展开更多
A typical Ti（C, N）-based cermet and another cermet with grain growth inhibitor Cr3C2 were studied using scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, energy dispersive X-ray analys...A typical Ti（C, N）-based cermet and another cermet with grain growth inhibitor Cr3C2 were studied using scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, energy dispersive X-ray analysis （EDX）. The two cermets have a “core-rim” structure. The structure is formed by dissolution of small ceramic grains and precipitation of （Ti, Mo, W）（C, N） around the remaining TiC core. Most of chromium element congregated in the rim phase when Cr3C2 was added. During liquid phase sintering Cr3C2 solved in binder phase and congregated around the hard grains, which reduced the solubility of TiC in liquid phase, and consequently restrained the dissolution and reprecipitation, the grains were restrained from growing up during sintering.展开更多
The composition and structure of substrate materials have important influences on coating performance,especially in terms of bond-ing strength and coating hardness,which determine whether the coating can be used for a...The composition and structure of substrate materials have important influences on coating performance,especially in terms of bond-ing strength and coating hardness,which determine whether the coating can be used for a given application.In this study,a TiAlN coating is deposited on Ti(C,N)-based cermet(TC)substrates with 0wt%-20wt%WC by arc ion plating.The influence of cermet substrate characterist-ics on the structure and properties of the TiAlN coating is then researched.Results show that the TiAlN coating deposited on the TC substrate has a columnar grain structure.As WC increases,the strength ratio of I(111)/I(200)and adhesive strength of TiAlN gradually increases.In the ab-sence of WC in the substrate,the preferred orientation of the TiAlN coating is(200).As WC increases,the preferred orientation of the TiAlN coating becomes(111)and(200).Notable differences in adhesive strength between the coating and substrate could be attributed to the micro-structure and composition of the latter.Scratching results show that the adhesive strengths of the TiAlN coating on the 0wt%-20wt%WC cer-met substrate are 52-65 N.Among the coatings obtained that on the TC substrate with 15wt%WC presents the highest H/E and H3/E2,which indicates that this coating also features the best wear resistance.The failure mechanisms of the coated tools include coating peeling,adhesive wear,and abrasive wear.As the cutting speed increases,the degree of flank wear increases and the durability of the coating decreases accord-ingly.Increases in WC result in an initial decrease followed by a gradual increase in the flank wear of the coated cermet inserts.展开更多
The availability using oxygen-rich powders to prepare ultrafine Ti(C,N)-based cermets was investigated. The deoxidation process, denitrification phenomenon and the effect of deoxidation on microstructure and mechanica...The availability using oxygen-rich powders to prepare ultrafine Ti(C,N)-based cermets was investigated. The deoxidation process, denitrification phenomenon and the effect of deoxidation on microstructure and mechanical properties of sintered samples were discussed, respectively. The results show that oxygen in the samples prepared even with high oxygen contained in starting powders can be almost completely cleaned away through suitable sintering process. The ultrafine oxygen-rich powders have a significant effect on microstructure, which promotes the formation of white core phase. A ultrafine Ti(C,N)-based cermet with mean particle size of 0. 30 μm, uniform microstructure and excellent mechanical properties is successfully prepared. It is also found that there exists severe denitrification phenomenon in the preparation process of ultrafine Ti(C,N)-based cermet.展开更多
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 microsmictures 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.
基金This work wasfinancially supported by the National Natural Science Foundation Of China (50074017), the NationalDoctorate Progr
文摘The submicron powder mixtures of TiC-TiN-WC-Mo-C-Ni sintered at 1400℃ or below in vacuum were studied by X-ray diffration （XRD）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM） analyses. The results showed that Mo2C fOrmed at 800℃ or below. Both WC and Mo2C disappeared at 1200 ℃, and TiN disappeared at 1250℃. In addihon, the variahons of lanice constans of the htanium carbonitride and nickel binder phase with sintering temperature were experimentally obtained, and the reason was analyzed.
基金This project was supported by Australian Research Council(DP180100731,DP 180100568)JSPS Joint Research Project(Open Partnership)under bilateral program between Japan and Australia(FY 2019-FY2020,DG 1270).
文摘High temperature solid oxide fuel cell(SOFC)is the most efficient and clean energy conversion technology to electrochemically convert the chemical energy of fuels such as hydrogen,natural gas and hydrocarbons to electricity,and also the most viable alternative to the traditional thermal power plants.However,the power output of a SOFC critically depends on the characteristics and performance of its key components:anode,electrolyte and cathode.Due to the highly reducing environment and strict requirements in electrical conductivity and catalytic activity,there are limited choices in the anode materials of SOFCs,particularly for operation in the intermediate temperature range of 500–800C.Among them,Ni-based cermets are the most common and popular anode materials of SOFCs.The objective of this paper is to review the development of Ni-based anode materials in SOFC from the viewpoints of materials microstructure,performance and industrial scalability associated with the fabrication and optimization processes.The latest advancement in nano-structure architecture,contaminant tolerance and interface optimization of Ni-based cermet anodes is presented.And at the end of this paper,we propose and appeal for the collaborative work of scientists from different disciplines that enable the inter-fusion research of fabrication,microanalysis and modelling,aiming at the challenges in the development of Ni-based cermet anodes for commercially viable intermediate temperature SOFC or IT-SOFC technologies.
基金supported by the Coal Seam Gas Joint Foundation of Shanxi(2015012016)Shanxi Province Science Foundation(2016011025)+2 种基金Shanxi Scholarship Council of China(2016-010)Shanxi “1331 Project” Key Innovative Research Team(“1331KIRT”)the Open Funding from State Key Laboratory of Materialoriented Chemical Engineering(No.KL16-03)
文摘Ni-based anodes of SOFCs are susceptible to coking, which greatly limits practical application of direct methane-based fuels. An indirect internal reformer is an effective way to convert methane-based fuels into syngas before they reach anode. In this work, catalytic activity of a redox-stable perovskite La0.7Sr0.3Cr0.8Fe0.2O3-δ(LSCrFO) for methane conversion was evaluated. The catalyst was fabricated as an anodic protective layer to improve coking resistance of a Ni cermet anode. Using wet CH4 as a fuel, the LSCrFO-modified cell showed excellent power output and good coking resistance with peak power density of 1.59 W cm-2 at 800℃. The cell demonstrated good durability lasting for at least 100 h. While the bare cell without the protective layer showed poor durability with the cell voltage fast dropped from 0.75 V to 0.4 V within 30 min. Under wet coal bed methane (CBM) operation, obvious performance degradation within 35 h (1.7 mV h^-1) was observed due to the influence of heavy carbon compounds in CBM. The pre-and post-mortem microstructures and carbon analysis of the anode surface and catalyst surface were further conducted.
文摘The enriching of metals to the center of sample was found and investigated during the sinterprocess of the cermet.The enrichment is caused by addition with Y<sub>2</sub>O<sub>3</sub>.The enriching of copper is greatly in-fluenced by sinter temperature and time.The enriching of metal can significantly enhance the electrical con-ductivity of the cermet.
基金Funded by the National Natural Science Foundation of China(Nos.21571095,51404157)the Zhejiang Provincial Natural Science Foundation of China(No.LY17E050003)+2 种基金the Taizhou Science and Technology Project(No.15gy54)the Open Research Program of Zhejiang Provincial Key Laboratory for Cutting Tools(No.ZD201501)the Open Foundation of Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology and the Public Projects of Zhejiang Province(Nos.2017C31118,2016C31049)
文摘Ti(C,N)-TiB2 cermets were fabricated from Ti(C,N), TiB2, Co and WC powder mixtures via a vacuum hot pressing process. The influence of TiB2 content on their microstructures and mechanical properties was investigated. As a result of the elevated TiB2 contents, two types of corerim microstructures were present in the Ti(C,N)-TiB2 cermets, and remarkably improved mechanical properties were achieved. With the increase of TiB2 content, the flexural strength, fracture toughness and hardness of the Ti(C,N)-TiB2 cermets first increased, and then decreased, while their relative density consistently decreased. Attributed to an integration of the intergranular and intrangranular fracture behaviors, the Ti(C,N)-TiB2 cermets with 20 wt% TiB2 content exhibited the best overall properties with the relative density, hardness, fracture toughness and flexural strength at 99.3%, 1 995 HV, 7.92 MPa·m1/2 and 1 114 MPa, respectively. The underlying mechanism for their enhanced properties was studied in detail.
文摘The dense TiC Fe cermets were produced by self propagating high temperature synthesis and pseudo hot isostatic pressing(SHS/PHIP). The influence of Fe content on the combustion temperature, combustion velocity, density and microstructure of products was studied. The composition and microstructure of the product were analyzed. The results showed that the cermet consists of quasi spherical TiC particles and Fe binder phases. A thin diffusion layer was found between Fe binder phase and TiC particle. In the range of 10%～20% Fe content, the combustion temperature and velocity decrease more slowly than the other contributions.
文摘TiAl alloys were joined to TiC cermets using combustion synthesis method. The Ti-C-Ni metallic powder compact acted as a joining interlayer in the joining process. The identification and mechanisms of the reaction at the interface and interlayer were investigated. From the analysis of the microstructure of TiAl/TiC cermet joint, it is noted that TiC and TiNi compounds are main reaction products and unreacted Ni is observed in the interlayer. The reaction products consist of a large volume of voids or unreacted regions. It is confirmed that Al addition as well as joining pressure are effective to decrease the voids. It is considered that high flowability of liquid Al enhances the SHS reaction and the densification of reaction products. There is a continuous Ni-rich layer observed at the interface between the interlayer and TiC cermets substrate. Ti3Al, TiC and TiNi compounds are observed in the reaction products.
文摘Stress concentration zones and the maximum value of thermal stress of TiC cermet/iron joint brazed with Ag-Cu-Zn filler metal during cooling were studied. The results show that when the temperature is 300K, the maximum values of shear stress and tensile stress on TiC cermet/iron interface both appear on the tip of Ag-Cu-Zn/iron interface, which makes Ag-Cu-Zn/iron interface become weak zone of the interface. Tensile stress on iron undersurface relaxes to the inner of iron, and the compression stress on iron undersurface concentrates on the side of iron as the temperature decreases, so cracks appear easily at the site where tensile and compression stress cross.
文摘The variations of chemical compositions, phases, microstructure evolution and shrinking of cermets compact debinded in H2 or in vacuum and sintered subsequently in vacuum were studied systematically using chemical analysis, back scattering scanning electron microscopy (SEM), and X-ray diffractometry (XRD). The total carbon of cermets debinded in H2 is lower than that debinded in vacuum by 0.4%-0.5%. The contents of carbon and oxygen are decreased sharply when being sintered at 1 100-1 300 ℃. The decomposition reaction of nitrogen is conducted sharply at 1 300 ℃. However, the decomposition of nitrogen is inhibited while the liquid phase appears, and then begins again above 1 500 ℃. The solution reaction of TaC and Mo2C into ring phase starts at 1 200 ℃, and WC into ring phase at 1 300 ℃ is finished. Therefore, the heating rate during sintering of cermets between 900 ℃ and 1 350 ℃ is important.
文摘The microstructure and mechanical properties of Ti(C, N)-based cermets with different content Mo were studied. Different Mo contents were added into Ti(C, N)-based cermets. Effect of sintering temperature on mechanical properties of the cermets was also investigated. Specimens were fabricated by conventional powder metallurgy techniques and vacuum sintered at different temperatures. The microstructure and the fracture morphology were investigated using scanning electron microscope. Transverse strength and hardness were measured. The results show that the microstructure is uniform and the thickness of rim phase is moderate when the content of Mo is 8%. The mechanical properties are the best when the content of Mo is 8% and the sintering temperature is 1450℃.
文摘Fe-Cr-C cermet was prepared by reaction sintering of ferrochromium and graphite. The exothermic reaction was determined by DTA. The effect of carbon content on the porosity, hardness and oxidation resistance was investigated. The result showed that the cermet with 6 %-7 % of carbon has high hardness and oxidation resistance.
文摘Effect of two-stage sintering parameters such as heating rate, top sintering temperature and holding time, sintering temperature and holding time at the second stage on relative density, transverse rupture strength(TRS) and microstructures of powder injection molded Ti(C, N)-based cermets were investigated, by means of Archimedes’s method, three-point bending test and micrographic analysis. The results show that the optimum sintering cycle for powder injection molded Ti(C, N)-based cermets comprises rapid heating (10℃/min) at low temperatures, slow heating (5℃/min) at intermediate temperatures, holding at the highest sintering temperature (1420℃) for a short time (10min), and holding at the second stage (1360℃) for a longer time (6h) to avoid grain coarsening, and that its TRS reaches 624MPa, and there are little pores in their microstructures.
文摘Cu-Cu2O cermets were prepared via hot pressing（HP） or in situ reduction hot pressing （ISPHP）. The results of electric conductivity tests show that the percolation threshold of the cermet, which is prepared by HP, is lower than that of cermet prepared by ISRHP. The electric conductivity and the percolation threshold depend on four influencing factors: the content, the size, the shape and the distribution of Cu phase. The electric conductivity decreases with the increase of Cu particle size, and decrease of the aspect ratio of Cu particle. The more even the Cu phase distribution, the higher the electric conductivity of the cermets.
文摘A typical Ti（C, N）-based cermet and another cermet with grain growth inhibitor Cr3C2 were studied using scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, energy dispersive X-ray analysis （EDX）. The two cermets have a “core-rim” structure. The structure is formed by dissolution of small ceramic grains and precipitation of （Ti, Mo, W）（C, N） around the remaining TiC core. Most of chromium element congregated in the rim phase when Cr3C2 was added. During liquid phase sintering Cr3C2 solved in binder phase and congregated around the hard grains, which reduced the solubility of TiC in liquid phase, and consequently restrained the dissolution and reprecipitation, the grains were restrained from growing up during sintering.
基金the National Nat-ural Science Foundation of China(Nos.51634006 and 51901195)the National Science and Technology Major Project of China(No.2019ZX04007001)+1 种基金the Science and Technology Major Project of Sichuan Province(No.2020ZDZX0022)the SCU-Zi Gong Project(No.2019CDZG-1).
文摘The composition and structure of substrate materials have important influences on coating performance,especially in terms of bond-ing strength and coating hardness,which determine whether the coating can be used for a given application.In this study,a TiAlN coating is deposited on Ti(C,N)-based cermet(TC)substrates with 0wt%-20wt%WC by arc ion plating.The influence of cermet substrate characterist-ics on the structure and properties of the TiAlN coating is then researched.Results show that the TiAlN coating deposited on the TC substrate has a columnar grain structure.As WC increases,the strength ratio of I(111)/I(200)and adhesive strength of TiAlN gradually increases.In the ab-sence of WC in the substrate,the preferred orientation of the TiAlN coating is(200).As WC increases,the preferred orientation of the TiAlN coating becomes(111)and(200).Notable differences in adhesive strength between the coating and substrate could be attributed to the micro-structure and composition of the latter.Scratching results show that the adhesive strengths of the TiAlN coating on the 0wt%-20wt%WC cer-met substrate are 52-65 N.Among the coatings obtained that on the TC substrate with 15wt%WC presents the highest H/E and H3/E2,which indicates that this coating also features the best wear resistance.The failure mechanisms of the coated tools include coating peeling,adhesive wear,and abrasive wear.As the cutting speed increases,the degree of flank wear increases and the durability of the coating decreases accord-ingly.Increases in WC result in an initial decrease followed by a gradual increase in the flank wear of the coated cermet inserts.
基金Project(50323008) supported by the National Natural Science Foundation of China
文摘The availability using oxygen-rich powders to prepare ultrafine Ti(C,N)-based cermets was investigated. The deoxidation process, denitrification phenomenon and the effect of deoxidation on microstructure and mechanical properties of sintered samples were discussed, respectively. The results show that oxygen in the samples prepared even with high oxygen contained in starting powders can be almost completely cleaned away through suitable sintering process. The ultrafine oxygen-rich powders have a significant effect on microstructure, which promotes the formation of white core phase. A ultrafine Ti(C,N)-based cermet with mean particle size of 0. 30 μm, uniform microstructure and excellent mechanical properties is successfully prepared. It is also found that there exists severe denitrification phenomenon in the preparation process of ultrafine Ti(C,N)-based cermet.
