Abstract This study investigates the chemical changes of the surface of Alloy 800HT during sliding contact under helium atmosphere in the presence of impurities at 750 °C, which is of interest for the nuclear industry. The alloy samples are exposed to helium (He) atmosphere at high temperature for long duration of 500 h to identify the chemical and topographical changes of the alloy surface. The oxidation rate constant is reported based on the weight change data. For the tribo-experimental samples, the surfaces inside and outside the wear track are studied thoroughly using techniques such as secondary electron microscopy, energy dispersive spectroscopy, x-ray diffraction, Raman spectroscopy and secondary ion mass spectroscopy. The formation and evolution of surface oxides are discussed in He atmosphere, compared with air. The presence of Fe-rich thin layer of oxide on top of a thicker Cr-rich oxide and a mixed spinel-based inner layer on the bulk is found. The persistent presence of thicker Fe3O4 in the wear track in high temperature air proved to be the reason of lower friction property. Pre-oxidation of the samples in air or He does not improve but worsen the tribological behavior in He atmosphere.

中文翻译：

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不纯氦环境下高温滑动接触下800HT合金的摩擦化学变化

摘要 本研究调查了合金 800HT 在 750 °C 下存在杂质的情况下在氦气环境下滑动接触过程中表面的化学变化，这对核工业很重要。合金样品在高温下暴露于氦 (He) 气氛中 500 小时，以识别合金表面的化学和形貌变化。基于重量变化数据报告氧化速率常数。对于摩擦实验样品，使用二次电子显微镜、能量色散光谱、X 射线衍射、拉曼光谱和二次离子质谱等技术彻底研究磨损轨迹内外的表面。与空气相比，在 He 气氛中讨论了表面氧化物的形成和演化。发现在较厚的富铬氧化物顶部存在富铁氧化物薄层，在主体上存在混合尖晶石基内层。高温空气中磨损轨迹中持续存在较厚的 Fe3O4 被证明是较低摩擦性能的原因。样品在空气或 He 中的预氧化不会改善而是恶化 He 气氛中的摩擦学行为。