In this study, a Cr coating was fabricated on Ni-based alloys to prevent under-deposit corrosion. The effect of salt deposition on the structural integrity of the Cr coating in SCW environment with/without oxygen was investigated. Results show that the Cr coating kept its integrity after exposure in SCW environment, successfully avoided the metallic ions leaching from Ni-based alloys. The structure of the oxide layer after exposure is a thin FeO or FeCrO layer and a CrO layer. The oxidation rate of the Cr coating decreased to one third of the sample after exposure in the same environment without salt deposit layer, indicating that the inward mass-transfer of oxygen to the alloy surface was inhibited by the salt deposit layer. The volume expansion of the sample due to the growth of Cr oxide layer was restrained by the salt deposit layer, forming a growth stress in the coating.

中文翻译：

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500℃超临界水氧化环境下镀铬镍基合金的沉积下腐蚀

在这项研究中，在镍基合金上制备了铬涂层，以防止沉积下腐蚀。研究了在有/无氧的 SCW 环境中盐沉积对 Cr 涂层结构完整性的影响。结果表明，暴露于超临界水环境后，Cr涂层保持了完整性，成功避免了镍基合金中金属离子的浸出。曝光后氧化层的结构是薄的FeO或FeCrO层和CrO层。在没有盐沉积层的相同环境中暴露后，Cr涂层的氧化速率降低至样品的三分之一，表明氧向合金表面的向内传质受到盐沉积层的抑制。由于Cr氧化物层生长而引起的样品体积膨胀受到盐沉积层的抑制，在镀层中形成生长应力。