| GUO Yu,ZHANG Ying-qiao,ZHANG Tao,LIU Sheng-yao.Microstructures and Properties of Laser Cladding Al/Zr+B4C/Y2O3 Composite Coatings on AZ91D Magnesium Alloys[J],47(1):176-180 |
| Microstructures and Properties of Laser Cladding Al/Zr+B4C/Y2O3 Composite Coatings on AZ91D Magnesium Alloys |
| Received:July 19, 2017 Revised:January 20, 2018 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2018.01.027 |
| KeyWord:laser cladding magnesium alloy ZrC Y2O3 microhardness corrosion resistance |
| Author | Institution |
| GUO Yu |
School of Materials Science and Engineering, North University of China, Taiyuan , China |
| ZHANG Ying-qiao |
School of Materials Science and Engineering, North University of China, Taiyuan , China |
| ZHANG Tao |
School of Materials Science and Engineering, North University of China, Taiyuan , China |
| LIU Sheng-yao |
School of Materials Science and Engineering, North University of China, Taiyuan , China |
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| Abstract: |
| The work aims to improve hardness and corrosion resistance of the surface of magnesium alloys. AZ91D magnesium alloy was coated with Zr/B4C/Y2O3 mixed powder, and then laser cladding was applied to substrate surface with Nd:YAG solid laser. Morphology and phase composition of the coatings were analyzed with optical microscope (OM), scanning electron microscope (SEM) and X-ray diffractometer (XRD). Hardness and corrosion resistance of the coatings were measured with microhardness tester and electrochemical workstation. The coatings mainly contained ZrC, intermetallic compounds such as Al3Zr and Al12Mg17, and rare earth compounds including Al3Y. Though there were some tiny pores in the coating with 0.8%Y2O3, pores disappeared in the coating with 1.6%Y2O3. Precipitates were mainly in the form of particles and bars. For the purpose of reducing surface area and surface energy, some precipitates gathered together for development. Overall hardness distribution curve of the coatings was graded, the hardness of the top of coatings was the highest (coating with 0.8%Y2O3 is 306.10HV, coating with 1.6%Y2O3 is 310.15HV). Average hardness of the coatings with 0.8%Y2O3 and with 1.6%Y2O3 was 291.613HV and 294.495HV, respectively, which was 4 times higher than that of the substrate. Self-corrosion potential of the coatings with 0.8%Y2O3 and with 1.6%Y2O3 was −1.269 V and −1.215 V, respectively, and self-corrosion current density was 7.655×10−5 A/cm2 and 2.048×10−6 A/cm2, respectively. Corrosion resistance of the coatings was obviously improved compared with the substrate. The presence of various ceramic phases, intermetallic compounds and rare earth compounds in the coatings remarkably improves the hardness and corrosion resistance of the composite coatings. |
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