Abstract CoCrFeNiNbx (x = 0 or 1 at.%) high-entropy alloy (HEA) coatings with good metallurgical bonding were successfully prepared on surfaces of pure titanium sheets by pulsed laser cladding. Phase constitutions and microstructural characteristics of the HEA coatings were characterized and analyzed by combined use of X-ray diffraction, electron channeling contrast imaging, energy dispersive spectroscopy and electron backscatter diffraction techniques. Results show that the HEA coating without Nb is consisted of BCC solid-solution phase with equiaxed bulk grain morphology and Cr2Ti Laves phase (C14-type hexagonal structure) with fine interdendritic lamellar morphology. After adding 1 at.% Nb, in addition to the BCC solid-solution phase and the Cr2Ti Laves phase, Cr2Nb Laves phase with C15-type cubic structure also appears in the interdendritic region in the HEA coating. Hardness tests reveal that the CoCrFeNiNbx HEA coatings are significantly harder than the pure titanium substrate (~122 HV). The hardness value of the HEA coating with 1 at.% Nb reaches 1008 HV, which is ~ 8.3 times that of the substrate and considerably higher than that of bulk HEAs with similar compositions. Such high hardness can be attributed to the combined contribution from solid-solution hardening, and hardening from grain refinement and Laves phases with fine lamellar morphologies.

中文翻译：

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脉冲激光熔覆纯钛基体上CoCrFeNiNbx高熵合金涂层的显微组织特征和性能

摘要 采用脉冲激光熔覆技术在纯钛薄板表面成功制备了具有良好冶金结合的CoCrFeNiNbx (x = 0 or 1 at.%)高熵合金(HEA)涂层。结合X射线衍射、电子通道对比成像、能量色散光谱和电子背散射衍射技术对HEA涂层的相组成和微观结构特征进行了表征和分析。结果表明，不含 Nb 的 HEA 涂层由具有等轴块状晶粒形态的 BCC 固溶体相和具有精细枝晶间层状形态的 Cr2Ti Laves 相（C14 型六方结构）组成。添加1 at.% Nb后，除BCC固溶相和Cr2Ti Laves相外，具有 C15 型立方结构的 Cr2Nb Laves 相也出现在 HEA 涂层的枝晶间区域。硬度测试表明，CoCrFeNiNbx HEA 涂层比纯钛基材 (~122 HV) 硬得多。含有 1 at.% Nb 的 HEA 涂层的硬度值达到 1008 HV，是基材硬度值的 8.3 倍，远高于具有相似成分的块状 HEA。如此高的硬度可归因于固溶硬化、晶粒细化和具有精细层状形态的 Laves 相的硬化的综合贡献。是基材的 3 倍，远高于具有类似成分的体相 HEA。如此高的硬度可归因于固溶硬化、晶粒细化和具有精细层状形态的 Laves 相的硬化的综合贡献。是基材的 3 倍，远高于具有类似成分的体相 HEA。如此高的硬度可归因于固溶硬化、晶粒细化和具有精细层状形态的 Laves 相的硬化的综合贡献。