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    TC4钛合金表面激光熔覆CuNiFeTiAl高熵合金的组织及硬度

    Microstructure and Hardness of Laser Cladding CuNiFeTiAl High-Entropy Alloy on TC4 Titanium Alloy

    • 摘要: 在激光功率300~800 W、扫描速度2~6 mm·s−1、送粉速率5~35 g·min−1条件下,在TC4钛合金基板表面激光熔覆单道CuNiFeTiAl高熵合金,研究了熔覆合金的组织和硬度。结果表明:激光功率过高(800 W)时合金中出现贯穿性裂纹;扫描速度过低(2 mm·s−1)时合金内部出现开裂和过烧;送粉速率大于15 g·min−1时,合金内部萌生裂纹。当激光功率400 W、扫描速度4 mm·s−1和送粉速率15 g·min−1时,合金与基体形成良好冶金结合,未见裂纹、孔隙等缺陷,综合成形质量最佳,故确定为最佳工艺。在最佳工艺条件下,熔覆合金组织主要由等轴枝晶组成,枝晶干组织为(Fe,Ni)和(Al,Ni)固溶体,枝晶间形成富钛固溶体;合金与基板结合界面出现富钛的柱状晶过渡区。最佳工艺激光熔覆高熵合金的显微硬度约为TC4钛合金基板的1.85倍,界面过渡区硬度最高,达678.3 HV。

       

      Abstract: Under laser power of 300‒800 W, scanning speed of 2‒6 mm·s−1, and powder feeding rate of 5‒35 g·min−1, CuNiFeTiAl high-entropy alloy was prepared on surface of TC4 titanium alloy plate by single-track laser cladding. The microstructure and hardness of the alloy were investigated. The results show that penetrating cracks appeared in the alloy under excessive laser power (800 W), internal cracking and over-burning occurred at low scanning speed (2 mm·s−1), and cracks initiated within the alloy under the powder feeding rate exceeding 15 g·min−1. Under a laser power of 400 W, scanning speed of 4 mm·s−1, and powder feeding rate of 15 g·min−1, the alloy exhibited sound metallurgical bonding with the substrate, and no cracks or pores were observed, representing the overall optimal forming quality; these parameters were identified as the optimal process. The alloy microstructure mainly consisted of equiaxed dendrites by laser cladding with the optimal process parameters. The dendritic trunks consisted of (Fe, Ni) and (Al, Ni) solid solutions, and a titanium-rich solid solution was forned in the interdendritic regions. A titanium-rich columnar crystal transition zone appeared at the coating-substrate interface. The microhardness of the alloy by laser cladding with the optimal process parameters was approximately 1.85 times that of the substrate, and the highest hardness observed in the interfacial transition zone, reaching 678.3 HV.

       

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