A novel design of micro-aluminum(μAl)powder coated with bi-/tri-component alloy layer,such as:Ni-P and Ni-P-Cu(namely,Al@Ni-P,Al@Ni-P-Cu,respectively),as combustion catalysts,were introduced to release its huge energ...A novel design of micro-aluminum(μAl)powder coated with bi-/tri-component alloy layer,such as:Ni-P and Ni-P-Cu(namely,Al@Ni-P,Al@Ni-P-Cu,respectively),as combustion catalysts,were introduced to release its huge energy inside Al-core and promote rapid pyrolysis of ammonium perchlorate(AP)at a lower temperature in aluminized propellants.The microstructure of Al@Ni-P-Cu demonstrates that a three-layer Ni-P-Cu shell,with the thickness of~100 nm,is uniformly supported byμAl carrier(fuel unit),which has an amorphous surface with a thickness of~2.3 nm(catalytic unit).The peak temperature of AP with the addition of Al@Ni-P-Cu(3.5%)could significantly drop to 316.2℃ at high-temperature thermal decomposition,reduced by 124.3℃,in comparison to that of pure AP with 440.5℃.It illustrated that the introduction of Al@Ni-P-Cu could weaken or even eliminate the obstacle of AP pyrolysis due to its reduction of activation energy with 118.28 kJ/mol.The laser ignition results showed that the ignition delay time of Al@Ni-P-Cu/AP mixture with 78 ms in air is shorter than that of Al@Ni-P/AP(118 ms),decreased by 33.90%.Those astonishing breakthroughs were attributed to the synergistic effects of adequate active sites on amorphous surface and oxidation exothermic reactions(7597.7 J/g)of Al@Ni-P-Cu,resulting in accelerated mass and/or heat transfer rate to catalyze AP pyrolysis and combustion.Moreover,it is believed to provide an alternative Al-based combustion catalyst for propellant designer,to promote the development the propellants toward a higher energy.展开更多
为提高热轧态0Cr21A16合金板材的组织均匀性和塑性,以改善其高温性能及冷加工特性,分析研究了不同温度的热处理试验及组织性能。采用光学显微镜、X射线衍射仪、Gleeble高温热拉伸实验、扫描电镜和纳米压痕仪等研究了热处理前后0Cr21Al6...为提高热轧态0Cr21A16合金板材的组织均匀性和塑性,以改善其高温性能及冷加工特性,分析研究了不同温度的热处理试验及组织性能。采用光学显微镜、X射线衍射仪、Gleeble高温热拉伸实验、扫描电镜和纳米压痕仪等研究了热处理前后0Cr21Al6合金板材的显微组织和力学性能。结果表明,通过热处理的方式改善0Cr21Al6合金板材的组织均匀性,在960℃保温6 min 40 s后快速冷却,晶粒平均尺寸为42μm,整体的晶粒尺寸相对于940、980、1000、1020℃热处理后较为均匀、细小,硬度和塑性达到最佳匹配,断裂韧度KIC在960℃处理下达到最佳,拥有最佳的综合性能,可有效避免生产过程中材料的脆性断裂问题。另外Gleeble实验显示1000℃以上的热处理温度不再适合于热加工。展开更多
The safety and reliability of weapon systems would be significantly affected by changes in the performance of energetic materials due to ambient temperature and humidity.Nanothermites have promising applications due t...The safety and reliability of weapon systems would be significantly affected by changes in the performance of energetic materials due to ambient temperature and humidity.Nanothermites have promising applications due to their excellent reactivity.Therefore it becomes extremely important to understand their aging and failure process in the environment before using them.Here,the aging and failure process of Al/CuO in 71°C/60%RH were investigated,and showed that CuO nanoparticles negatively catalyze Al nanopowders,resulting in rapid hydration.The anti-aging effect of FAS-17-coated Al nanopowder was also examined.The aging process of Al,Al/CuO,and Al@FAS-17/CuO in high humidity and heat environment were revealed by quasi-in situ SEM and TEM methods.Compared with the aging of pure Al,the Al nanopowder in the nanothermites strongly agglomerated with the CuO nanopowder and hydrated earlier.This may be caused by CuO catalyzed hydration of Al nanopowder.The energy release experiments showed that the performance of Al/CuO decreased rapidly and failed to ignite after 4 h of aging.In contrast,the Al@FAS-17/CuO thermite can achieve long-term stability of up to 60 h in the same environment by simple cladding of FAS-17.It is found that FAS-17 coated Al nanopowder can prevent both particle agglomeration and water erosion,which is an effective means to make nanothermites application in high humidity and heat environment.展开更多
A wear resistant （Cr, Fe）7C3/γ-Fe ceramalcomposite coating wasfabricatedon substrate of a 0.45% C carbon steel by plasma transferred arc （PTA） cladding process using the Fe-Cr-C elemental powder blends. The micro...A wear resistant （Cr, Fe）7C3/γ-Fe ceramalcomposite coating wasfabricatedon substrate of a 0.45% C carbon steel by plasma transferred arc （PTA） cladding process using the Fe-Cr-C elemental powder blends. The microstructure, microhardness and dry sliding wear resistance of the coating were evaluated. Results indicate that the plasma transferred arc clad ceramal composite coating has a rapidly solidified microstructure consisting of blocky primary （Cr, Fe）7C3 and the interblocky （ Cr, Fe）7C3/γ-Fe eutectics and is metallurgically bonded to the 0.45%C carbon steel substrate. The ceramal composite coating has high hardness and excellent wear resistance under dry sliding wear test condition.展开更多
Cored wires for electric arc spraying of Al/Al 2 O 3 MMC coatings were developed, with Al 2 O 3 powder as the core material and commercial aluminium strip as the retaining sheath. The bond strength, ...Cored wires for electric arc spraying of Al/Al 2 O 3 MMC coatings were developed, with Al 2 O 3 powder as the core material and commercial aluminium strip as the retaining sheath. The bond strength, Al 2 O 3 content, microstructure, micro-hardness and wear resistance of coatings produced by arc spraying of the cored wires were experimentally investigated and were compared with those of pure aluminum coating.展开更多
A wear-resistant （Cr, Fe）7C3/γ-Fe in situ ceramal composite coating was fabricated on the substrate of 0.45wt%C carbon steel by a plasma-transferred arc cladding process using the Fe-Cr-C elemental powder blends. T...A wear-resistant （Cr, Fe）7C3/γ-Fe in situ ceramal composite coating was fabricated on the substrate of 0.45wt%C carbon steel by a plasma-transferred arc cladding process using the Fe-Cr-C elemental powder blends. The microstructure, microhardness, and dry-sliding wear resistance of the coating were evaluated. The results indicate that the microstructure of the coating, which was composed of （Cr, Fe）7C3 primary phase uniformly distributed in the γ-Fe, and the （Cr, Fe）7C3 eutectic matrix was metallurgically bonded to the 0.45wt%C carbon steel substrate. From substrate to coating, the microstructure of the coating exhibited an evident epitaxial growth character. The coating, indehiscent and tack-free, had high hardness and appropriate gradient. It had excellent wear resistance under the dry sliding wear test condition.展开更多
Coating structural materials with Fe 3Al based intermetallics may rapidly lead to industrial application of their environment and wear resistant features. In the present study, high velocity arc spraying (HVAS) was u...Coating structural materials with Fe 3Al based intermetallics may rapidly lead to industrial application of their environment and wear resistant features. In the present study, high velocity arc spraying (HVAS) was used to in situ synthesize Fe 3Al intermetallic coating. The microstructural characterization and properties of the coating have been investigated. The microstructure was found to consist of Fe 3Al based intermetallic (D0 3 and B2) and α Fe regions together with fine oxide (α Al 2O 3) layers. TEM images of coating show that the solidified lamellae are polycrystalline and have a grain size of the order of about 150 nm , and there also exists amorphous state in some areas. It can be concluded that a very high cooling rate has been obtained during HVAS process. Moreover, the coating has relatively higher adhesion strength and microhardness, as well as lower density and porosity.展开更多
Cr1-xAlxN coatings have been deposited on a Ti3Al based alloy by reactive sputtering method. The results of the isothermal oxidation test at 800-900℃ showed that Cr1-xAlxN coatings could remarkably reduce the oxidati...Cr1-xAlxN coatings have been deposited on a Ti3Al based alloy by reactive sputtering method. The results of the isothermal oxidation test at 800-900℃ showed that Cr1-xAlxN coatings could remarkably reduce the oxidation rate of the alloy owing to the formation of Al2O3＋Cr2O3 mixture oxide scale on the surface of the coatings. No spallation of the coatings or oxide scales took place during the cyclic oxidation at 800℃. Ti was observed to diffuse into the coatings, the diffusion distance of which was very short, and the diffusion ability of it was proportional to the AI content in the coatings. Compared to Ti, Nb can diffuse much more easily through the whole coatings and oxide scales.展开更多
Cr-Al-Si-N coatings were deposited on SUS 304 substrate by a hybrid coating system. A Cr interlayer was introduced between Cr-Al-Si-N coating and SUS 304 substrate to improve the coating adherence. The effects of Cr i...Cr-Al-Si-N coatings were deposited on SUS 304 substrate by a hybrid coating system. A Cr interlayer was introduced between Cr-Al-Si-N coating and SUS 304 substrate to improve the coating adherence. The effects of Cr interlayer on the microhardness, adhesion, and tribological behavior of Cr-Al-Si-N coatings were systematically investigated. The results indicate that the microhardness of the Cr-Al-Si-N coatings gradually deceases with increasing thickness of Cr interlayers. The adhesion between Cr-Al-Si-N and SUS 304 substrate is improved by addition of the Cr interlayers. A peak critical load of ~50 N is observed for the coating containing Cr interlayer of 60 nm as compared ~ 20 N for the coating without Cr interlayer. The thicker Cr interlayers result in reduced critical load values. Moreover, the wear resistance of the Cr-Al-Si-N coatings is greatly enhanced by introducing the Cr interlayer with thickness of 60 nm in spite of the decreased microhardness. The friction coefficient of the coating system is also moderately reduced.展开更多
In this paper, Ni-Cr-Al-Y-Si coating deposited by vacuum are deposition on the Ni_3Alalloy IC6, the typical use of which is for turbine blades and vanes, was examined.The results of the tests show that the tensile pro...In this paper, Ni-Cr-Al-Y-Si coating deposited by vacuum are deposition on the Ni_3Alalloy IC6, the typical use of which is for turbine blades and vanes, was examined.The results of the tests show that the tensile properties at room temperature and stress rupture properties at 1100℃ of the IC6 alloy were not obviously influenced by the coatings. At annealing state, limited element interdiffusion was observed. After stress rupture testing for 252 h at 1100℃/90 MPa, however,significant interdiffusion of Mo, Cr and Al took place between the coating layer and the substrate.The element diffustion did not result in the formation of brittle phases on the coating/substrate interface. No cracking and spallation in the coating were found.Therefore it can be concluded that the Ni-Cr-Al-Y-Si overlay coating was successful for protecting the IC6 alloy.展开更多
High-temperature titanium alloy for aeroengine compressor applications suffers from high-temperature oxidation and environmental corrosion, which prohibits long-term service of this kind alloy at temperatures above 60...High-temperature titanium alloy for aeroengine compressor applications suffers from high-temperature oxidation and environmental corrosion, which prohibits long-term service of this kind alloy at temperatures above 600℃. In an attempt to tackle this problem, Ti-48Al （at. pct） and Ti-48Al-12Cr （at. pct） protective coatings were plated on the substrate of alloy Ti-60 by arc ion plating （ALP） method. Isothermal and cyclic oxidation tests were performed in static air at elevated temperatures. Phase composition, morphology of the coatings and distribution of elements were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and energy dispersive X-ray analysis （EDX）. The results showed that the Ti-48Al coating exhibited good isothermal oxidation resistance during exposure at 800℃, but poorer resistance against oxidation at 900℃. By contrast Ti-48Al-12Cr coating demonstrated excellent isothermal oxidation resistance at both temperatures. Cyclic oxidation tests performed at 800℃ indicated that resistance and no spallation of coatings was observed. But both coatings demonstrated good cyclic oxidation at 900℃ only Ti-48Al-12Cr coating demonstrated excellent cyclic oxidation resistance.展开更多
The effect of sputtered Ti-50Al-10Cr and Ti-50A1-20Cr coatings on both isothermal and cyclic oxidation resistance at 800-900℃ and hot corrosion resistance at 850℃ of Ti-24Al-14Nb-3V was investigated. Results indicat...The effect of sputtered Ti-50Al-10Cr and Ti-50A1-20Cr coatings on both isothermal and cyclic oxidation resistance at 800-900℃ and hot corrosion resistance at 850℃ of Ti-24Al-14Nb-3V was investigated. Results indicated that Ti-24Al-14Nb-3V alloys exhibited poor oxidation resistance due to the formation of Al2O3+TiO2+AlNbO4 mixed scales in air at 800-900℃ and poor hot corrosion resistance due to the spoliation of scales formed in Na2SO4+K2SO4 melts at 850℃. Both Ti-50Al-10Cr and Ti-50Al-20Cr coatings remarkably improved the oxidation and hot corrosion resistance of Ti-24Al-14Nb-3V alloy.展开更多
基金supported by the National Natural Science Foundation of China,China(Grant Nos.U20B2018,U21B2086,11972087)。
文摘A novel design of micro-aluminum(μAl)powder coated with bi-/tri-component alloy layer,such as:Ni-P and Ni-P-Cu(namely,Al@Ni-P,Al@Ni-P-Cu,respectively),as combustion catalysts,were introduced to release its huge energy inside Al-core and promote rapid pyrolysis of ammonium perchlorate(AP)at a lower temperature in aluminized propellants.The microstructure of Al@Ni-P-Cu demonstrates that a three-layer Ni-P-Cu shell,with the thickness of~100 nm,is uniformly supported byμAl carrier(fuel unit),which has an amorphous surface with a thickness of~2.3 nm(catalytic unit).The peak temperature of AP with the addition of Al@Ni-P-Cu(3.5%)could significantly drop to 316.2℃ at high-temperature thermal decomposition,reduced by 124.3℃,in comparison to that of pure AP with 440.5℃.It illustrated that the introduction of Al@Ni-P-Cu could weaken or even eliminate the obstacle of AP pyrolysis due to its reduction of activation energy with 118.28 kJ/mol.The laser ignition results showed that the ignition delay time of Al@Ni-P-Cu/AP mixture with 78 ms in air is shorter than that of Al@Ni-P/AP(118 ms),decreased by 33.90%.Those astonishing breakthroughs were attributed to the synergistic effects of adequate active sites on amorphous surface and oxidation exothermic reactions(7597.7 J/g)of Al@Ni-P-Cu,resulting in accelerated mass and/or heat transfer rate to catalyze AP pyrolysis and combustion.Moreover,it is believed to provide an alternative Al-based combustion catalyst for propellant designer,to promote the development the propellants toward a higher energy.
文摘为提高热轧态0Cr21A16合金板材的组织均匀性和塑性,以改善其高温性能及冷加工特性,分析研究了不同温度的热处理试验及组织性能。采用光学显微镜、X射线衍射仪、Gleeble高温热拉伸实验、扫描电镜和纳米压痕仪等研究了热处理前后0Cr21Al6合金板材的显微组织和力学性能。结果表明,通过热处理的方式改善0Cr21Al6合金板材的组织均匀性,在960℃保温6 min 40 s后快速冷却,晶粒平均尺寸为42μm,整体的晶粒尺寸相对于940、980、1000、1020℃热处理后较为均匀、细小,硬度和塑性达到最佳匹配,断裂韧度KIC在960℃处理下达到最佳,拥有最佳的综合性能,可有效避免生产过程中材料的脆性断裂问题。另外Gleeble实验显示1000℃以上的热处理温度不再适合于热加工。
基金supported by the National Natural Science Foundation of China(Grant No.22275092)。
文摘The safety and reliability of weapon systems would be significantly affected by changes in the performance of energetic materials due to ambient temperature and humidity.Nanothermites have promising applications due to their excellent reactivity.Therefore it becomes extremely important to understand their aging and failure process in the environment before using them.Here,the aging and failure process of Al/CuO in 71°C/60%RH were investigated,and showed that CuO nanoparticles negatively catalyze Al nanopowders,resulting in rapid hydration.The anti-aging effect of FAS-17-coated Al nanopowder was also examined.The aging process of Al,Al/CuO,and Al@FAS-17/CuO in high humidity and heat environment were revealed by quasi-in situ SEM and TEM methods.Compared with the aging of pure Al,the Al nanopowder in the nanothermites strongly agglomerated with the CuO nanopowder and hydrated earlier.This may be caused by CuO catalyzed hydration of Al nanopowder.The energy release experiments showed that the performance of Al/CuO decreased rapidly and failed to ignite after 4 h of aging.In contrast,the Al@FAS-17/CuO thermite can achieve long-term stability of up to 60 h in the same environment by simple cladding of FAS-17.It is found that FAS-17 coated Al nanopowder can prevent both particle agglomeration and water erosion,which is an effective means to make nanothermites application in high humidity and heat environment.
文摘A wear resistant （Cr, Fe）7C3/γ-Fe ceramalcomposite coating wasfabricatedon substrate of a 0.45% C carbon steel by plasma transferred arc （PTA） cladding process using the Fe-Cr-C elemental powder blends. The microstructure, microhardness and dry sliding wear resistance of the coating were evaluated. Results indicate that the plasma transferred arc clad ceramal composite coating has a rapidly solidified microstructure consisting of blocky primary （Cr, Fe）7C3 and the interblocky （ Cr, Fe）7C3/γ-Fe eutectics and is metallurgically bonded to the 0.45%C carbon steel substrate. The ceramal composite coating has high hardness and excellent wear resistance under dry sliding wear test condition.
文摘Cored wires for electric arc spraying of Al/Al 2 O 3 MMC coatings were developed, with Al 2 O 3 powder as the core material and commercial aluminium strip as the retaining sheath. The bond strength, Al 2 O 3 content, microstructure, micro-hardness and wear resistance of coatings produced by arc spraying of the cored wires were experimentally investigated and were compared with those of pure aluminum coating.
文摘A wear-resistant （Cr, Fe）7C3/γ-Fe in situ ceramal composite coating was fabricated on the substrate of 0.45wt%C carbon steel by a plasma-transferred arc cladding process using the Fe-Cr-C elemental powder blends. The microstructure, microhardness, and dry-sliding wear resistance of the coating were evaluated. The results indicate that the microstructure of the coating, which was composed of （Cr, Fe）7C3 primary phase uniformly distributed in the γ-Fe, and the （Cr, Fe）7C3 eutectic matrix was metallurgically bonded to the 0.45wt%C carbon steel substrate. From substrate to coating, the microstructure of the coating exhibited an evident epitaxial growth character. The coating, indehiscent and tack-free, had high hardness and appropriate gradient. It had excellent wear resistance under the dry sliding wear test condition.
文摘Coating structural materials with Fe 3Al based intermetallics may rapidly lead to industrial application of their environment and wear resistant features. In the present study, high velocity arc spraying (HVAS) was used to in situ synthesize Fe 3Al intermetallic coating. The microstructural characterization and properties of the coating have been investigated. The microstructure was found to consist of Fe 3Al based intermetallic (D0 3 and B2) and α Fe regions together with fine oxide (α Al 2O 3) layers. TEM images of coating show that the solidified lamellae are polycrystalline and have a grain size of the order of about 150 nm , and there also exists amorphous state in some areas. It can be concluded that a very high cooling rate has been obtained during HVAS process. Moreover, the coating has relatively higher adhesion strength and microhardness, as well as lower density and porosity.
基金the National Natural Science Foundation of China under grant Nos. 50371095 , 50571106.
文摘Cr1-xAlxN coatings have been deposited on a Ti3Al based alloy by reactive sputtering method. The results of the isothermal oxidation test at 800-900℃ showed that Cr1-xAlxN coatings could remarkably reduce the oxidation rate of the alloy owing to the formation of Al2O3＋Cr2O3 mixture oxide scale on the surface of the coatings. No spallation of the coatings or oxide scales took place during the cyclic oxidation at 800℃. Ti was observed to diffuse into the coatings, the diffusion distance of which was very short, and the diffusion ability of it was proportional to the AI content in the coatings. Compared to Ti, Nb can diffuse much more easily through the whole coatings and oxide scales.
基金supported by a grant from the National Core Research Center (NCRC) Program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (No. 2010-0001-226)a grant from the Fundamental R&D Program for Core Technology of Materials funded by the Ministry of Knowledge Economy, Republic of Korea
文摘Cr-Al-Si-N coatings were deposited on SUS 304 substrate by a hybrid coating system. A Cr interlayer was introduced between Cr-Al-Si-N coating and SUS 304 substrate to improve the coating adherence. The effects of Cr interlayer on the microhardness, adhesion, and tribological behavior of Cr-Al-Si-N coatings were systematically investigated. The results indicate that the microhardness of the Cr-Al-Si-N coatings gradually deceases with increasing thickness of Cr interlayers. The adhesion between Cr-Al-Si-N and SUS 304 substrate is improved by addition of the Cr interlayers. A peak critical load of ~50 N is observed for the coating containing Cr interlayer of 60 nm as compared ~ 20 N for the coating without Cr interlayer. The thicker Cr interlayers result in reduced critical load values. Moreover, the wear resistance of the Cr-Al-Si-N coatings is greatly enhanced by introducing the Cr interlayer with thickness of 60 nm in spite of the decreased microhardness. The friction coefficient of the coating system is also moderately reduced.
文摘In this paper, Ni-Cr-Al-Y-Si coating deposited by vacuum are deposition on the Ni_3Alalloy IC6, the typical use of which is for turbine blades and vanes, was examined.The results of the tests show that the tensile properties at room temperature and stress rupture properties at 1100℃ of the IC6 alloy were not obviously influenced by the coatings. At annealing state, limited element interdiffusion was observed. After stress rupture testing for 252 h at 1100℃/90 MPa, however,significant interdiffusion of Mo, Cr and Al took place between the coating layer and the substrate.The element diffustion did not result in the formation of brittle phases on the coating/substrate interface. No cracking and spallation in the coating were found.Therefore it can be concluded that the Ni-Cr-Al-Y-Si overlay coating was successful for protecting the IC6 alloy.
文摘High-temperature titanium alloy for aeroengine compressor applications suffers from high-temperature oxidation and environmental corrosion, which prohibits long-term service of this kind alloy at temperatures above 600℃. In an attempt to tackle this problem, Ti-48Al （at. pct） and Ti-48Al-12Cr （at. pct） protective coatings were plated on the substrate of alloy Ti-60 by arc ion plating （ALP） method. Isothermal and cyclic oxidation tests were performed in static air at elevated temperatures. Phase composition, morphology of the coatings and distribution of elements were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and energy dispersive X-ray analysis （EDX）. The results showed that the Ti-48Al coating exhibited good isothermal oxidation resistance during exposure at 800℃, but poorer resistance against oxidation at 900℃. By contrast Ti-48Al-12Cr coating demonstrated excellent isothermal oxidation resistance at both temperatures. Cyclic oxidation tests performed at 800℃ indicated that resistance and no spallation of coatings was observed. But both coatings demonstrated good cyclic oxidation at 900℃ only Ti-48Al-12Cr coating demonstrated excellent cyclic oxidation resistance.
文摘The effect of sputtered Ti-50Al-10Cr and Ti-50A1-20Cr coatings on both isothermal and cyclic oxidation resistance at 800-900℃ and hot corrosion resistance at 850℃ of Ti-24Al-14Nb-3V was investigated. Results indicated that Ti-24Al-14Nb-3V alloys exhibited poor oxidation resistance due to the formation of Al2O3+TiO2+AlNbO4 mixed scales in air at 800-900℃ and poor hot corrosion resistance due to the spoliation of scales formed in Na2SO4+K2SO4 melts at 850℃. Both Ti-50Al-10Cr and Ti-50Al-20Cr coatings remarkably improved the oxidation and hot corrosion resistance of Ti-24Al-14Nb-3V alloy.
