Conventional,submicron and multimodal WC-12Co cermet coatings were deposited by high velocity oxy-fuel（HVOF）.The microhardness and microstructure of the coatings were compared,and the resistance of the coatings to c...Conventional,submicron and multimodal WC-12Co cermet coatings were deposited by high velocity oxy-fuel（HVOF）.The microhardness and microstructure of the coatings were compared,and the resistance of the coatings to cavitation erosion was studied by ultrasonic vibration cavitation equipment.Cavitation pits and craters were observed by SEM and cavitation mechanisms were explored.The results show that the microstructures of submicron and multimodal WC-12Co coatings prepared by HVOF are dense with little porosity,and their microhardness values are obviously higher than that of the conventional WC-12Co coating.The average microhardness of multimodal WC-12Co coating reaches nearly HV1500,which is much higher than that of the conventional one.As well,it is found that the multimodal WC-12Co coating exhibits the best cavitation erosion resistance among the three coatings,the erosion rate is approximately 40% that of the conventional coating,and the cavitation erosion resistance of multimodal WC-12Co coating is enhanced by above 150% in comparison with the conventional coating.展开更多
A comprehensive study of the phase composition, microstructure evolution, microhardness and wear performance of WC-12 Co composite coatings fabricated by laser cladding using coaxial powder-feed mode was presented. It...A comprehensive study of the phase composition, microstructure evolution, microhardness and wear performance of WC-12 Co composite coatings fabricated by laser cladding using coaxial powder-feed mode was presented. It was shown that a combination of high scan speed and high laser energy density made WC on the edge of WC-12 Co composite powders partially melt in liquid Co and 304 stainless steel matrix, and then new carbides consisting of lamellar WC and herringbone M3 W3 C(M=Fe,Co) were formed. Meanwhile, WC-12 Co composite coatings with no porosity, cracks and drawbacks like decarburization were obtained, showing high densification and good metallurgical bonding with the substrate. Furthermore, a considerably high microhardness of HV0.3 1500-1600, low coefficient of friction of 0.55 and wear rate of(2.15±0.31)×10-7 mm3/(N·m) were achieved owing to the synergistic effect of excellent metallurgical bonding and fine microstructures of composite coating under laser power of 1500 W.展开更多
Zr/WC composite coating was prepared on the surface of Cr12MoV steel by electric spark deposition technology to change its surface properties. The surface and worn surface morphology of the coating were observed using...Zr/WC composite coating was prepared on the surface of Cr12MoV steel by electric spark deposition technology to change its surface properties. The surface and worn surface morphology of the coating were observed using scanning electron microscope. Dry friction and wear tests of the coatings were carried out at room temperature. The results show that the coating is continuous and uniform, and the thickness was about 50-60 μm. The microhardness of the coating surface was highest at 1140 HV_(200g), which was significantly higher than that of the substrate. The ear tests results show that the wear weight loss, wear volume and wear rate follow the following rules: Cr12MoV>WC coating> Zr/WC composite coating.展开更多
ZrO2-Y2O3 ceramic coating was produced by plasma electrolytic oxidation （PEO） on ZAlSil2Cu3Ni2 alloy. The microstructure and phase composition of the coating were investigated by SEM and XRD.： The results show that...ZrO2-Y2O3 ceramic coating was produced by plasma electrolytic oxidation （PEO） on ZAlSil2Cu3Ni2 alloy. The microstructure and phase composition of the coating were investigated by SEM and XRD.： The results show that adding an appropriate amount of yttrium ion can improve the growing rate of ceramic coating at different oxidation stages and decrease arc voltage. The thickness of ZrO2-Y2O3 coating is 16 μn thicker than that of ZrO2 coating and the maximum oxidation rate improves by 0.6 μm/min. In addition, the arc voltage decreases from 227 to 172 V. It can be seen that the rate of oxidation firstly increases to some extent and then decreases with the content of yttrium ion increasing. The growth rate reaches the maximum while the content of yttrium ion is 0.05 g-L-1The maximum thickness is 90 μm.Compared to ZrO2 coating, the micropores of ZrO2-Y2O3 coating are less and the ceramic layer is repeatedly deposited by ZrO2 and Y2O3 ceramic particles. Meanwhile, the binding force between coating and substrate is better and the coating is uniform and compact. The ceramic layer is mainly composed of c-Y0.15Zr0.85O1.93□0.07, m-ZrO2, α-Al2O3, ,γ-Al2O3 and Y2O3. It is indicated that ZrO2 has beert fully stabilized by yttrium ion through the formation of solid solution.展开更多
The ceramic coatings containing zirconium dioxide were grown in-situ on LY12 aluminium alloy by micro-arc oxidation in mixed zirconate and phosphate solution. The phase composition and morphology of the coatings were ...The ceramic coatings containing zirconium dioxide were grown in-situ on LY12 aluminium alloy by micro-arc oxidation in mixed zirconate and phosphate solution. The phase composition and morphology of the coatings were studied by XRD and SEM. The adhesive strength of ceramic coatings was assessed by thermal shock test and tensile test. The results show that the coating is composed of m-ZrO2,t-ZrO2, and a littleγ-Al2O3. Along the section of the coating, t-ZrO2 is more on both sides than that in the middle, while m-ZrO2 is more in the middle than that on both sides. Meantime the coating is also composed of a dense layer and a loose layer. The coating has excellent thermal shock resistance under 550℃and 600℃. And tensile tests show the adhesive strength of the dense layer of the coating with the substrate is more than 17.5 MPa.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
基金Project(50479016) supported by the National Natural Science Foundation of China
文摘Conventional,submicron and multimodal WC-12Co cermet coatings were deposited by high velocity oxy-fuel（HVOF）.The microhardness and microstructure of the coatings were compared,and the resistance of the coatings to cavitation erosion was studied by ultrasonic vibration cavitation equipment.Cavitation pits and craters were observed by SEM and cavitation mechanisms were explored.The results show that the microstructures of submicron and multimodal WC-12Co coatings prepared by HVOF are dense with little porosity,and their microhardness values are obviously higher than that of the conventional WC-12Co coating.The average microhardness of multimodal WC-12Co coating reaches nearly HV1500,which is much higher than that of the conventional one.As well,it is found that the multimodal WC-12Co coating exhibits the best cavitation erosion resistance among the three coatings,the erosion rate is approximately 40% that of the conventional coating,and the cavitation erosion resistance of multimodal WC-12Co coating is enhanced by above 150% in comparison with the conventional coating.
基金Project(20171ACE50018)supported by the Key Research and Development Program of Jiangxi Province,ChinaProject(2017-YZD2-16)supported by the Key Research Project of Jiangxi Academy of Sciences,China。
文摘A comprehensive study of the phase composition, microstructure evolution, microhardness and wear performance of WC-12 Co composite coatings fabricated by laser cladding using coaxial powder-feed mode was presented. It was shown that a combination of high scan speed and high laser energy density made WC on the edge of WC-12 Co composite powders partially melt in liquid Co and 304 stainless steel matrix, and then new carbides consisting of lamellar WC and herringbone M3 W3 C(M=Fe,Co) were formed. Meanwhile, WC-12 Co composite coatings with no porosity, cracks and drawbacks like decarburization were obtained, showing high densification and good metallurgical bonding with the substrate. Furthermore, a considerably high microhardness of HV0.3 1500-1600, low coefficient of friction of 0.55 and wear rate of(2.15±0.31)×10-7 mm3/(N·m) were achieved owing to the synergistic effect of excellent metallurgical bonding and fine microstructures of composite coating under laser power of 1500 W.
基金supported by Key Projects of Strategic International Scientific and Technological Innovation Cooperation(Grant No.2016YFE0201300)
文摘Zr/WC composite coating was prepared on the surface of Cr12MoV steel by electric spark deposition technology to change its surface properties. The surface and worn surface morphology of the coating were observed using scanning electron microscope. Dry friction and wear tests of the coatings were carried out at room temperature. The results show that the coating is continuous and uniform, and the thickness was about 50-60 μm. The microhardness of the coating surface was highest at 1140 HV_(200g), which was significantly higher than that of the substrate. The ear tests results show that the wear weight loss, wear volume and wear rate follow the following rules: Cr12MoV>WC coating> Zr/WC composite coating.
基金Funded by the National Natural Science Foundation of China(No.51401155)the School Foundation(No.XAGDXJJ1012)The Open Fund of Shaanxi Key Laboratory of Photoelectric Functional Materials and Devices(No.ZSKJ201416)
文摘ZrO2-Y2O3 ceramic coating was produced by plasma electrolytic oxidation （PEO） on ZAlSil2Cu3Ni2 alloy. The microstructure and phase composition of the coating were investigated by SEM and XRD.： The results show that adding an appropriate amount of yttrium ion can improve the growing rate of ceramic coating at different oxidation stages and decrease arc voltage. The thickness of ZrO2-Y2O3 coating is 16 μn thicker than that of ZrO2 coating and the maximum oxidation rate improves by 0.6 μm/min. In addition, the arc voltage decreases from 227 to 172 V. It can be seen that the rate of oxidation firstly increases to some extent and then decreases with the content of yttrium ion increasing. The growth rate reaches the maximum while the content of yttrium ion is 0.05 g-L-1The maximum thickness is 90 μm.Compared to ZrO2 coating, the micropores of ZrO2-Y2O3 coating are less and the ceramic layer is repeatedly deposited by ZrO2 and Y2O3 ceramic particles. Meanwhile, the binding force between coating and substrate is better and the coating is uniform and compact. The ceramic layer is mainly composed of c-Y0.15Zr0.85O1.93□0.07, m-ZrO2, α-Al2O3, ,γ-Al2O3 and Y2O3. It is indicated that ZrO2 has beert fully stabilized by yttrium ion through the formation of solid solution.
基金Project(50171026) supported by the National Natural Science Foundation of ChinaProject (SKLT04-08) supported by the State Key Laboratory of Tribology, Tsinghua University, China
文摘The ceramic coatings containing zirconium dioxide were grown in-situ on LY12 aluminium alloy by micro-arc oxidation in mixed zirconate and phosphate solution. The phase composition and morphology of the coatings were studied by XRD and SEM. The adhesive strength of ceramic coatings was assessed by thermal shock test and tensile test. The results show that the coating is composed of m-ZrO2,t-ZrO2, and a littleγ-Al2O3. Along the section of the coating, t-ZrO2 is more on both sides than that in the middle, while m-ZrO2 is more in the middle than that on both sides. Meantime the coating is also composed of a dense layer and a loose layer. The coating has excellent thermal shock resistance under 550℃and 600℃. And tensile tests show the adhesive strength of the dense layer of the coating with the substrate is more than 17.5 MPa.
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.
