A composite ceramic coating containing Y2O3-ZrO2-MgO（YSZ-MgO） was prepared on AZ91D magnesium alloy,which was immersed in Y（NO3）3 aqueous solution as pretreatment,by micro-arc oxidation（MAO） process.The morpholo...A composite ceramic coating containing Y2O3-ZrO2-MgO（YSZ-MgO） was prepared on AZ91D magnesium alloy,which was immersed in Y（NO3）3 aqueous solution as pretreatment,by micro-arc oxidation（MAO） process.The morphology,elemental and phase compositions,corrosion behavior and thermal stability of the coatings were studied by SEM,EDX,XRD,electrochemical corrosion test,high temperature oxidation and thermal shock test.The results show that the coating mainly consists of ZrO2,Y2O3,MgO,Mg2SiO4,and MgF2.Among these compounds,Y2O3 accounts for 26.7% of（Y2O3 ＋ ZrO2）.The thickness of YSZ-MgO coating is smaller than that of ZrO2-MgO coating,but its compactness and surface roughness are better than those of ZrO2-MgO coating.YSZ-MgO coating has a good corrosion resistance,and its corrosion rate in 5% NaCl aqueous solution is lower than that of ZrO2-MgO and only about 8.5% of that of AZ91D magnesium alloy.After oxidation at 410 °C,the mass gain of AZ91D magnesium alloy presents a linear increase with the oxidation time.The YSZ-MgO coating and ZrO2-MgO coating can remarkably decrease the oxidation mass gain.The oxidation mass gain of YSZ-MgO coating is lower than that of ZrO2-MgO coating,especially during a long oxidation period.The thermal shock resistance of YSZ-MgO coating is superior to ZrO2-MgO coating.展开更多
Boronizing was applied to Inconel 718. In order to obtain the optimal combination of strength and ductility, the borided Inconel 718 was subjected to standard heat treatment. This consists of solution treatment and th...Boronizing was applied to Inconel 718. In order to obtain the optimal combination of strength and ductility, the borided Inconel 718 was subjected to standard heat treatment. This consists of solution treatment and then a two-step aging treatment. The borided layer is composed of the compound layer and the boron diffusion zone. Because of the superior hardness of borides, the borided Inconel 718 exhibits a significant reduction in its wear rate and relatively low coefficient of friction （COF） compared with the unborided Inconel 718. The standard heat treatment efficiently promotes the diffusion of boron into the interior of the material and the generation of new borides （Fe2B, CrB）. The borided layer with standard heat treatment shows much better wear resistance due to the thicker borided layer （313.76 μm）.展开更多
Al2O3 thermal barrier coatings with different TiO2 contents were deposited on 6061 aluminum alloy by plasma spraying. The corrosion resistance, thermal insulation property and phase composition of these coatings were ...Al2O3 thermal barrier coatings with different TiO2 contents were deposited on 6061 aluminum alloy by plasma spraying. The corrosion resistance, thermal insulation property and phase composition of these coatings were investigated. The results indicate that all the feedstock powders exhibit phase transformation during the spray process. With the increase of the TiO2 content in the powder, the corrosion resistance of the coating is enhanced but the thermal insulation property is decreased. This can be attributed to the higher thermal conductivity but lower melting point and brittleness of TiO2 than those of Al2O3, so it is easy for TiO2 to disperse in the brittle Al2O3 substrate during spraying, in which these dispersively distributed TiO2 play the role of hole sealing, releasing stress and reducing cracks.展开更多
The application of semisolid process was investigated on Pb-Sb alloys that are normally used for metallic parts in car batteries, in order to increase their mechanical properties and corrosion resistance.The semisolid...The application of semisolid process was investigated on Pb-Sb alloys that are normally used for metallic parts in car batteries, in order to increase their mechanical properties and corrosion resistance.The semisolid behaviour of a Pb-4%Sb alloy was analysed by means of rheological and calorimetry differential scanning experiments.The alloy was melted, treated by ultrasound to obtain the semisolid state and then poured into permanent moulds.Some of these samples were also heated in semisolid temperature range and injected in thixo-casting apparatus.Both poured and injected samples were characterized by metallographic analysis, mechanical test and electrochemical corrosion experiments.The results show an improvement of mechanical and corrosion resistance with respect to samples obtained by conventional casting technique.展开更多
基金Project (gf200901002) support by the National Defense Key Disciplines Laboratory of Light Alloy Processing Science and Technology of Nanchang Hangkong University,China
文摘A composite ceramic coating containing Y2O3-ZrO2-MgO（YSZ-MgO） was prepared on AZ91D magnesium alloy,which was immersed in Y（NO3）3 aqueous solution as pretreatment,by micro-arc oxidation（MAO） process.The morphology,elemental and phase compositions,corrosion behavior and thermal stability of the coatings were studied by SEM,EDX,XRD,electrochemical corrosion test,high temperature oxidation and thermal shock test.The results show that the coating mainly consists of ZrO2,Y2O3,MgO,Mg2SiO4,and MgF2.Among these compounds,Y2O3 accounts for 26.7% of（Y2O3 ＋ ZrO2）.The thickness of YSZ-MgO coating is smaller than that of ZrO2-MgO coating,but its compactness and surface roughness are better than those of ZrO2-MgO coating.YSZ-MgO coating has a good corrosion resistance,and its corrosion rate in 5% NaCl aqueous solution is lower than that of ZrO2-MgO and only about 8.5% of that of AZ91D magnesium alloy.After oxidation at 410 °C,the mass gain of AZ91D magnesium alloy presents a linear increase with the oxidation time.The YSZ-MgO coating and ZrO2-MgO coating can remarkably decrease the oxidation mass gain.The oxidation mass gain of YSZ-MgO coating is lower than that of ZrO2-MgO coating,especially during a long oxidation period.The thermal shock resistance of YSZ-MgO coating is superior to ZrO2-MgO coating.
基金Projects(2011CB013402,201303002,2014028002)supported by the National Basic Research Program of China
文摘Boronizing was applied to Inconel 718. In order to obtain the optimal combination of strength and ductility, the borided Inconel 718 was subjected to standard heat treatment. This consists of solution treatment and then a two-step aging treatment. The borided layer is composed of the compound layer and the boron diffusion zone. Because of the superior hardness of borides, the borided Inconel 718 exhibits a significant reduction in its wear rate and relatively low coefficient of friction （COF） compared with the unborided Inconel 718. The standard heat treatment efficiently promotes the diffusion of boron into the interior of the material and the generation of new borides （Fe2B, CrB）. The borided layer with standard heat treatment shows much better wear resistance due to the thicker borided layer （313.76 μm）.
基金Project(51271099)supported by the National Natural Science Foundation of China
文摘Al2O3 thermal barrier coatings with different TiO2 contents were deposited on 6061 aluminum alloy by plasma spraying. The corrosion resistance, thermal insulation property and phase composition of these coatings were investigated. The results indicate that all the feedstock powders exhibit phase transformation during the spray process. With the increase of the TiO2 content in the powder, the corrosion resistance of the coating is enhanced but the thermal insulation property is decreased. This can be attributed to the higher thermal conductivity but lower melting point and brittleness of TiO2 than those of Al2O3, so it is easy for TiO2 to disperse in the brittle Al2O3 substrate during spraying, in which these dispersively distributed TiO2 play the role of hole sealing, releasing stress and reducing cracks.
文摘The application of semisolid process was investigated on Pb-Sb alloys that are normally used for metallic parts in car batteries, in order to increase their mechanical properties and corrosion resistance.The semisolid behaviour of a Pb-4%Sb alloy was analysed by means of rheological and calorimetry differential scanning experiments.The alloy was melted, treated by ultrasound to obtain the semisolid state and then poured into permanent moulds.Some of these samples were also heated in semisolid temperature range and injected in thixo-casting apparatus.Both poured and injected samples were characterized by metallographic analysis, mechanical test and electrochemical corrosion experiments.The results show an improvement of mechanical and corrosion resistance with respect to samples obtained by conventional casting technique.
