| ZHOU Haifei,LI Fengrui,WANG He,QIAN Dahu,YU Lutao,CHI Yiming,YAO Jianhua.Microstructure and Properties of Laser Surface Alloying Anti-wear/Corrosion Coating on Q235 Steel Surface for Electric Power Fitting[J],53(21):208-219 |
| Microstructure and Properties of Laser Surface Alloying Anti-wear/Corrosion Coating on Q235 Steel Surface for Electric Power Fitting |
| Received:November 06, 2023 Revised:December 25, 2023 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.21.021 |
| KeyWord:laser alloying electric power fitting WC reinforced particles wear resistance corrosion resistance |
| Author | Institution |
| ZHOU Haifei |
Research Institute, State Grid Zhejiang Electric Power Co., Ltd., Hangzhou , China |
| LI Fengrui |
Research Institute, State Grid Zhejiang Electric Power Co., Ltd., Hangzhou , China |
| WANG He |
Research Institute, State Grid Zhejiang Electric Power Co., Ltd., Hangzhou , China |
| QIAN Dahu |
Institute of Laser Advanced Manufacturing, Zhejiang University of Technology, Hangzhou , China |
| YU Lutao |
Institute of Laser Advanced Manufacturing, Zhejiang University of Technology, Hangzhou , China |
| CHI Yiming |
Institute of Laser Advanced Manufacturing, Zhejiang University of Technology, Hangzhou , China |
| YAO Jianhua |
Institute of Laser Advanced Manufacturing, Zhejiang University of Technology, Hangzhou , China |
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| Abstract: |
| Considering the deterioration of electric power fittings caused by wear and corrosion, the work aims to employ a laser surface alloying process to prepare uniform and dense K500 or K500+WC composite coatings on the surface of Q235 steel, a widely utilized material for power fittings. Comparative analysis was conducted on the microstructure, phase composition, wear resistance and corrosion resistance of these coatings. The dissolution and precipitation behavior of WC particles in composite coating was also discussed. The surface of the substrate was polished and cleaned with sandpaper, and the K500 powder was spread evenly on the surface with a thickness of 0.8 mm with a jig and a coating tool. Laser alloying experiments were carried out with a semiconductor laser (YLS-2000), and the optimized laser parameters were laser power of 1 200 W, scanning speed of 6 mm/s, spot diameter of 4.2 mm, and overlap rate of 30%. For the preparation of K500+WC composite coating, the K500 powder was similarly pre-placed on the substrate. Simultaneously, WC particles were directly introduced into the molten pool through synchronous powder feeding under the same laser process parameters. The powder feeding rate was set at 10 g/min. The experimental process was carried out within a high-purity argon atmosphere protection chamber with an argon flow rate of 10 L/min. The microstructure of the coatings was observed with a scanning electron microscope (ZEISS EVO18), and the composition analysis was carried out with an attached energy spectrometer (Nano Xflash Detector 5010). An X-ray diffractometer (D/max-Ultima Ⅳ) was used to identify the phase constituents of the coatings. The microhardness was tested by Vickers microhardness tester (HMV-2T) at a load of 200 g for 15 s. Dry friction and wear tests were carried out at room temperature with a ball-on-disc wear tester (HT-1000) at a load of 60 N and a speed of 200 r/min. After a 60 min test, the three-dimensional morphologies and cross-section profiles of the worn surface were measured by a laser confocal microscope (VK-X1000). The corrosion resistance of the composite coatings was tested with an electrochemical workstation (CHI760E). The K500 coating was mainly composed of γ- (Fe, Ni, Cu) single-phase solid solution with a transition from planar crystals to columnar crystals, dendrites, and equiaxed crystals in the structure. After addition of WC particles, the coating mainly consisted of γ phase, WC, W2C and Fe3W3C. In the molten pool, WC particles partially dissolved from the edge and formed a diffusion interface, within which dendritic and blocky carbides precipitated. The combined effects of solid solution strengthening of the γ-phase alloy and dispersion strengthening of the carbide reinforcements resulted in high hardness of K500 and K500+WC coatings. The wear rates of the two coatings were 58.45 μm3/(N.mm) and 14.59 μm3/(N.mm), decreasing by 41.48% and 85.39% compared to the substrate. For K500+WC coatings, the impact of shear stress led to localized fracture of WC edges, forming chips that integrated into abrasive particles, consequently creating grooves on the coating surface. However, the overall shape of the WC particles remained essentially unchanged due to their inherent high hardness, which played a crucial role in preventing the coating from cutting and deforming during the wear process. Additionally, the existence of Ni and Cu in the γ-phase of K500 coating formed dense oxide films during the initial stage of corrosion, isolating the coating from the corrosive medium and effectively reducing the corrosion rate. K500 coating exhibited the best corrosion resistance. After the addition of WC particles, the corrosion resistance of the K500+WC coating decreases slightly due to the reduction of corrosion-resistant γ-phase and the increased micro-interfaces and corrosion pathways. However, it still exhibits significant improvement in corrosion resistance than the substrate. |
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