Abstract High temperature resistant coating is becoming a key technique to improve the heat resistance of aerospace heat-resistant components. In this paper, Ti6Al4V/Inconel625 gradient coating was fabricated by laser melting deposition. The results show that the microstructure changes with composition gradient, from lamellar structure consisting of lamellar α and β phases to equiaxed structure. With the increase of the proportion for nickel-based alloy, alloying elements and concentration of solute increase in molten pool. Furthermore, the nucleation rate increases due to the increase of alloying elements, which leads to the microstructure refinement. The phase composition of gradient coating changes in the sequence of α + β → α + β + Ti2Ni → Ti2Ni + β → Ti2Ni + CrNi2 + γ-Ni. The hardness of gradient coating increases as the relative percentage of Inconel625 correspondingly. When the relative percentage of nickel-based alloy reaches 100%, the hardness reaches a peak of 855 HV1. The hardness is attributed to the contribution from the formation of Ti2Ni precipitates, CrNi2 compounds as well as the solid solution hardening. For the high temperature properties, there is a diffusion zone at the interface between Ti6Al4V base layer and transition layer. The transverse microcracks are produced between layers at 800 °C.

中文翻译：

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激光熔融沉积制备Ti6Al4V/Inconel625梯度涂层的组织演变及耐高温性能

摘要 耐高温涂层正成为提高航天耐热部件耐热性的关键技术。本文采用激光熔化沉积制备 Ti6Al4V/Inconel625 梯度涂层。结果表明，显微组织随成分梯度变化，由层状α相和β相组成的层状结构转变为等轴结构。随着镍基合金比例的增加，熔池中合金元素和溶质浓度增加。此外，由于合金元素的增加，形核率增加，从而导致显微组织细化。梯度涂层的相组成按α+β→α+β+Ti2Ni→Ti2Ni+β→Ti2Ni+CrNi2+γ-Ni的顺序变化。梯度涂层的硬度随着Inconel625的相对百分比增加而相应增加。当镍基合金的相对百分比达到100%时，硬度达到855 HV1的峰值。硬度归因于形成 Ti2Ni 沉淀、CrNi2 化合物以及固溶硬化的贡献。对于高温性能，在 Ti6Al4V 基层和过渡层的界面处有一个扩散区。横向微裂纹是在 800 °C 的层间产生的。对于高温性能，Ti6Al4V基层与过渡层界面处存在扩散区。横向微裂纹是在 800 °C 的层间产生的。对于高温性能，在 Ti6Al4V 基层和过渡层的界面处有一个扩散区。横向微裂纹是在 800 °C 的层间产生的。