Niobium‑chromium (NbCr) carbide coatings were deposited on graphite using the thermo-reactive deposition and diffusion (TRD) technique. The microstructure, hardness, and coefficient of thermal expansion were characterized to search for the optimal treatment parameters for hard and adherent coatings on graphite. The growth rate increased with treatment temperature for fixed treatment duration and remained constant at a constant temperature for about 6 h. The coatings were found to consist of alternating Nb and Cr layers, and this interesting multilayer structure might be explained by the thermodynamics of oxide reduction and carbide formation reactions. Compared to the single-carbides layer, the hardness of the complex coatings increased from about 2500 HV to above 3000 HV, and displayed a smaller gradient of the depth-dependent hardness from the coating to the substrate. The variation of coefficient of thermal expansion of the samples with temperature was similar to that of the graphite substrate at temperatures from 40 to 450 °C. These results showed the effectiveness of the TRD method for synthesizing hard and adherent carbide coatings on graphite, and for other coating/substrate systems with sharply dissimilar mechanical properties.

铌铬（NbCr）碳化物涂层使用热反应沉积和扩散（TRD）技术沉积在石墨上。对微观结构、硬度和热膨胀系数进行表征，以寻找石墨上坚硬和粘附涂层的最佳处理参数。在固定的处理持续时间内，生长速率随处理温度而增加，并在恒定温度下保持恒定约 6 小时。发现涂层由交替的 Nb 和 Cr 层组成，这种有趣的多层结构可以用氧化物还原和碳化物形成反应的热力学来解释。与单碳化物层相比，复合涂层的硬度从约 2500 HV 增加到 3000 HV 以上，并显示出从涂层到基材的深度依赖硬度的较小梯度。样品的热膨胀系数随温度的变化与石墨基板在 40 至 450°C 的温度下的变化相似。这些结果显示了 TRD 方法在石墨上合成坚硬和粘附的碳化物涂层以及其他具有截然不同机械性能的涂层/基材系统的有效性。