Over the past years, great achievements have been made in the development of coating technologies for surface improvement of aluminum alloys. Despite these achievements, the role in the market strongly depends on the ...Over the past years, great achievements have been made in the development of coating technologies for surface improvement of aluminum alloys. Despite these achievements, the role in the market strongly depends on the ability of surface coating technology under technical and economic considerations to meet the increased demands for heavy tribological applications of aluminum alloys. Microplasma oxidation (MPO) technology has recently been studied as a novel and effective means to provide thick and hard ceramic coating with improved properties such as excellent load-bearing and wear resistance properties on aluminum alloys. The present work covers the evaluation of the performances of current single and duplex coatings combining MPO, physical vapor deposition (PVD), and plasma assisted chemical vapor deposition (PACVD) coatings on aluminum alloys. It suggests that the MPO coating is a promising candidate for design engineers to apply aluminum alloys to heavy load-bearing applications. The prospective future for the research on MPO coatings is introduced as well.展开更多
By using physical vapor deposition(PVD)to grow metallic nanorods,the characteristic length is controllable,which can be identified by two different growth modes:Mode I and Mode II.In Mode I,the growth of metallic nano...By using physical vapor deposition(PVD)to grow metallic nanorods,the characteristic length is controllable,which can be identified by two different growth modes:Mode I and Mode II.In Mode I,the growth of metallic nanorods is dominated by the monolayer surface steps.Whereas in Mode II,the growth mechanism is mainly determined by the multilayer surface steps.In this work,we focused on the analysis of the physical process of Mode I,in which the adatoms diffuse on the monolayer surface at beginning,then diffuse down to the next monolayer surface,and finally result in the metallic nanorods growth.Based on the physical process,both the variations of the characteristic length and the numerical solutions were theoretically proposed.In addition,the twodimensional(2 D)lattice kinetic Monte Carlo simulations were employed to verify the theoretical derivation of the metallic nanorods growth.Our results pay a new way for modifying the performance of metallic nanorods-based applications and devices.展开更多
Laminates with alternating layers of NiCoCrAlY and NiCr were fabricated by using electron beam physical vapor deposition (EB-PVD) method. The influence of the substrate temperature on morphology of the laminates was i...Laminates with alternating layers of NiCoCrAlY and NiCr were fabricated by using electron beam physical vapor deposition (EB-PVD) method. The influence of the substrate temperature on morphology of the laminates was investigated. The results show that in order to produce NiCoCrAlY/NiCr laminates with lower porosity, higher substrate temperature is required. The mechanical properties of the as-deposited samples and heat-treated samples were examined using tensile tests. The stress-strain curve of the as-deposited laminate shows a typical characteristic of multilayered materials and the fracture behavior is improved by annealing the samples at high temperatures. The tensile strength of the samples annealed at 760℃ is 658.4MPa, and the elongation reaches 6.2%.展开更多
The coatings of W-Ti carbides on the surface of diamond was obtained by using physical vapor deposition (PVD), during which WO3 powders pre-treated with hydrofluoric acid were reduced by titanium hydride in vacuum at ...The coatings of W-Ti carbides on the surface of diamond was obtained by using physical vapor deposition (PVD), during which WO3 powders pre-treated with hydrofluoric acid were reduced by titanium hydride in vacuum at 850 ℃. The resistance of diamond to corrosion at high-temperature was investigated. The formation of W-Ti carbides on the surface of diamond was verified by X-ray diffraction analysis, the interface state between diamond and matrix in metaLbase diamond composite was observed by scanning electron microscope. The results showed that the carbide coating is easy to be formed at low deposition temperature on the surface of diamond, while the resistance of diamond to corrosion at highutemperature and the strength of bonding between diarnond and metal matrix are effectively improved.展开更多
Zinc alloy coating attracted much attention due to its high anti-corrosive properties.Particularly,zinc alloy coatings containing magnesium was considered a promising metallic alloy due to a remarkable improvement of ...Zinc alloy coating attracted much attention due to its high anti-corrosive properties.Particularly,zinc alloy coatings containing magnesium was considered a promising metallic alloy due to a remarkable improvement of corrosion resistance.The proper magnesium content for Zn-Mg alloy coatings was studied.The samples were prepared using thermal evaporation method.The influence of Zn-Mg alloy coating on corrosion resistance was evaluated using immersion test,potentiodynamic test,and galvanic test in 3% NaCl solution at room temperature.The results show that the corrosion resistance of Zn-Mg alloy coatings is strongly dependent on magnesium content.Corrosion potential decreases with increasing magnesium content,whereas current density increases up to 15% magnesium content,and passivity region was found only in Zn-Mg coatings.展开更多
The performances of gradient thermal barrier coatings (GTBCs) produced by EB-PVD were evaluated by isothermal oxidation and cyclic hot corrosion (HTHC) tests. Compared with conventional two-layered TBCs, the GTBCs exh...The performances of gradient thermal barrier coatings (GTBCs) produced by EB-PVD were evaluated by isothermal oxidation and cyclic hot corrosion (HTHC) tests. Compared with conventional two-layered TBCs, the GTBCs exhibite better resistance to not only oxidation but also hot-corrosion. A dense Al2O3 layer in the GTBCs effectively prohibites inward diffusion of O and S and outward diffusion of Al and Cr during the tests. On the other hand, an "inlaid" interface, resulting from oxidation of the Al along the columnar grains of the bond coat, enhances the adherence of AI2O3 layer. Failure of the GTBC finally occurred by cracking at the interface between the bond coat and AI2O3 layer, due to the combined effect of sulfidation of the bond coat and thermal cvcling.展开更多
Thermal barrier coatings （TBCs） were developed to protect metallic blades and vanes working in turbo-engines. The two-layered structure TBCs, consisting of NiCoCrAlY bond coat and yttria stabilized zirconia （YSZ）,...Thermal barrier coatings （TBCs） were developed to protect metallic blades and vanes working in turbo-engines. The two-layered structure TBCs, consisting of NiCoCrAlY bond coat and yttria stabilized zirconia （YSZ）, were deposited on a cylinder of superalloy substrate by the electron beam-physical vapor deposition （EB-PVD）. The failure mechanism of the TBCs was investigated with a thermo-mechanical fatigue testing system under the service condition similar to that for turbine blades. Non-destructive evaluation of the coated specimens was conducted through the impedance spectroscopy. It is found that the crack initiation mainly takes place on the top coat at the edge of the heated zones.展开更多
文摘Over the past years, great achievements have been made in the development of coating technologies for surface improvement of aluminum alloys. Despite these achievements, the role in the market strongly depends on the ability of surface coating technology under technical and economic considerations to meet the increased demands for heavy tribological applications of aluminum alloys. Microplasma oxidation (MPO) technology has recently been studied as a novel and effective means to provide thick and hard ceramic coating with improved properties such as excellent load-bearing and wear resistance properties on aluminum alloys. The present work covers the evaluation of the performances of current single and duplex coatings combining MPO, physical vapor deposition (PVD), and plasma assisted chemical vapor deposition (PACVD) coatings on aluminum alloys. It suggests that the MPO coating is a promising candidate for design engineers to apply aluminum alloys to heavy load-bearing applications. The prospective future for the research on MPO coatings is introduced as well.
文摘By using physical vapor deposition(PVD)to grow metallic nanorods,the characteristic length is controllable,which can be identified by two different growth modes:Mode I and Mode II.In Mode I,the growth of metallic nanorods is dominated by the monolayer surface steps.Whereas in Mode II,the growth mechanism is mainly determined by the multilayer surface steps.In this work,we focused on the analysis of the physical process of Mode I,in which the adatoms diffuse on the monolayer surface at beginning,then diffuse down to the next monolayer surface,and finally result in the metallic nanorods growth.Based on the physical process,both the variations of the characteristic length and the numerical solutions were theoretically proposed.In addition,the twodimensional(2 D)lattice kinetic Monte Carlo simulations were employed to verify the theoretical derivation of the metallic nanorods growth.Our results pay a new way for modifying the performance of metallic nanorods-based applications and devices.
文摘Laminates with alternating layers of NiCoCrAlY and NiCr were fabricated by using electron beam physical vapor deposition (EB-PVD) method. The influence of the substrate temperature on morphology of the laminates was investigated. The results show that in order to produce NiCoCrAlY/NiCr laminates with lower porosity, higher substrate temperature is required. The mechanical properties of the as-deposited samples and heat-treated samples were examined using tensile tests. The stress-strain curve of the as-deposited laminate shows a typical characteristic of multilayered materials and the fracture behavior is improved by annealing the samples at high temperatures. The tensile strength of the samples annealed at 760℃ is 658.4MPa, and the elongation reaches 6.2%.
文摘The coatings of W-Ti carbides on the surface of diamond was obtained by using physical vapor deposition (PVD), during which WO3 powders pre-treated with hydrofluoric acid were reduced by titanium hydride in vacuum at 850 ℃. The resistance of diamond to corrosion at high-temperature was investigated. The formation of W-Ti carbides on the surface of diamond was verified by X-ray diffraction analysis, the interface state between diamond and matrix in metaLbase diamond composite was observed by scanning electron microscope. The results showed that the carbide coating is easy to be formed at low deposition temperature on the surface of diamond, while the resistance of diamond to corrosion at highutemperature and the strength of bonding between diarnond and metal matrix are effectively improved.
基金supported by the Smart Coating Steel Development Center,World Premier Materials (WPM) Program of the Ministry of Knowledge Economy of Korea and Korea Maritime University
文摘Zinc alloy coating attracted much attention due to its high anti-corrosive properties.Particularly,zinc alloy coatings containing magnesium was considered a promising metallic alloy due to a remarkable improvement of corrosion resistance.The proper magnesium content for Zn-Mg alloy coatings was studied.The samples were prepared using thermal evaporation method.The influence of Zn-Mg alloy coating on corrosion resistance was evaluated using immersion test,potentiodynamic test,and galvanic test in 3% NaCl solution at room temperature.The results show that the corrosion resistance of Zn-Mg alloy coatings is strongly dependent on magnesium content.Corrosion potential decreases with increasing magnesium content,whereas current density increases up to 15% magnesium content,and passivity region was found only in Zn-Mg coatings.
文摘The performances of gradient thermal barrier coatings (GTBCs) produced by EB-PVD were evaluated by isothermal oxidation and cyclic hot corrosion (HTHC) tests. Compared with conventional two-layered TBCs, the GTBCs exhibite better resistance to not only oxidation but also hot-corrosion. A dense Al2O3 layer in the GTBCs effectively prohibites inward diffusion of O and S and outward diffusion of Al and Cr during the tests. On the other hand, an "inlaid" interface, resulting from oxidation of the Al along the columnar grains of the bond coat, enhances the adherence of AI2O3 layer. Failure of the GTBC finally occurred by cracking at the interface between the bond coat and AI2O3 layer, due to the combined effect of sulfidation of the bond coat and thermal cvcling.
基金National Natural Science Foundation of China (50571005)
文摘Thermal barrier coatings （TBCs） were developed to protect metallic blades and vanes working in turbo-engines. The two-layered structure TBCs, consisting of NiCoCrAlY bond coat and yttria stabilized zirconia （YSZ）, were deposited on a cylinder of superalloy substrate by the electron beam-physical vapor deposition （EB-PVD）. The failure mechanism of the TBCs was investigated with a thermo-mechanical fatigue testing system under the service condition similar to that for turbine blades. Non-destructive evaluation of the coated specimens was conducted through the impedance spectroscopy. It is found that the crack initiation mainly takes place on the top coat at the edge of the heated zones.
