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激光重熔对In718熔覆层组织与性能的影响

Effect of laser remelting on microstructure and properties of In718 cladding layer

  • 摘要: 为了解决激光熔覆In718合金力学性能差的问题, 选择不同的扫描速率对In718合金熔覆层进行了激光重熔处理, 采用光学显微镜、扫描电镜和能谱仪观察显微组织结构和特征, 检测不同物相的成分并分析微观偏析对显微组织的影响, 通过力学检测设备对涂层的显微硬度与抗拉强度进行检测。结果表明, Laves相主要由Nb与Mo元素的偏析所导致, 与未重熔相比, 重熔后的涂层气孔明显减少, 且不同的重熔扫描速率对组织与性能的影响也不同, 4个涂层的Laves相体积分数由34.1%减少至24.6%、16.7%和19.6%, 平均硬度由250.3 HV提高至261.5 HV、276.9 HV和268.0 HV, 抗拉强度由678 MPa提高至728 MPa、879 MPa和808 MPa, 而重熔对涂层延伸率的影响不明显; 最优的重熔扫描速率为15 mm/s, Laves相的体积分数最低, 平均显微硬度和抗拉强度最高; 激光重熔能有效改善熔覆层的形貌、降低孔隙率、减少或抑制Laves相的析出, 并且减少Laves相有助于提高In718合金的力学性能。此研究为后续的离心球墨铸管模具的再制造奠定了理论基础。

     

    Abstract: In order to solve the problem of poor mechanical properties of laser cladding In718 alloy, different scanning speeds were selected to carry out laser remelting treatment of the cladding layer. Optical microscope, scanning electron microscope and energy dispersive spectrometer were used to observe the microstructure and characteristics and to detect the composition of different phases. The influence of microsegregation on the microstructure was then analyzed. The microhardness and tensile strength of the coating were tested by mechanical testing equipment. The results show that the Laves phase is mainly caused by the segregation of Nb and Mo elements. Compared with the non-remelted coating, the pores of the remelted coating are significantly reduced, and different remelting scanning speeds have different effects on the structure and properties. The Laves phase volume fraction of four coatings respectively decreased from 34.1% to 24.6%, 16.7%, and 19.6%, the average hardness respectively increased from 250.3 HV to 261.5 HV, 276.9 HV, and 268.0 HV. The tensile strength respectively increased from 678 MPa to 728 MPa, 879 MPa, and 808 MPa. However, the effect of remelted coating on elongation is not obvious. The optimum remelting scanning speed is 15 mm/s, which has the lowest Laves phase content and the highest average microhardness and tensile strength. Laser remelting can effectively improve the morphology of the cladding layer, reduce the porosity, reduce or inhibit the precipitation of Laves phase. Reducing the Laves phase to improve the mechanical properties of In718 alloy. This research establishes a theoretical foundation for the subsequent remanufacturing of centrifugal cast ductile iron pipes molds.

     

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