Oxidized zirconium alloys can appear as black, white and all gray shades depending on the heat treatment process. The black color results from a high amount of oxygen vacancies in non-stoichiometric zirconia (ZrO_2−x) that effectively reduces the band gap of the material. In this work we compare the surface properties of black and white zirconia on ZrNb7 substrate. An oxidation in air at 600 °C for 1 h results in a dark-gray oxide with only a few micro cracks. Oxidation at low oxygen partial pressure at 600 °C for 8 h (p_O2 = 10^–19 Pa) generates a dense, totally black oxide scale. A three step heat treatment process, that was introduced for better coating adhesion, results in a white oxide layer with many micro cracks parallel to the surface. From the results of various microscopy and spectroscopy techniques, we derive a model of the layer formation of zirconia on ZrNb7 and give reason why black zirconia, and therefore the oxidation at low oxygen partial pressure, is favorable for tribological applications (e.g., artificial joint replacements).

取决于热处理工艺，氧化锆合金可能显示为黑色，白色和所有灰色阴影。黑色是由于非化学计量氧化锆（ZrO _{2- x}）中大量的氧空位所致，有效地减小了材料的带隙。在这项工作中，我们比较了ZrNb7衬底上黑白氧化锆的表面性能。在600°C的空气中氧化1小时会产生暗灰色的氧化物，且只有很少的微裂纹。在600°C的低氧分压下氧化8 h（p _O2  = 10 ^–19 Pa）产生致密的全黑氧化皮。为了更好的涂层附着力而引入的三步热处理工艺导致白色氧化层具有许多平行于表面的微裂纹。从各种显微镜和光谱技术的结果中，我们得出了ZrNb7上氧化锆层形成的模型，并给出了为什么黑色氧化锆以及因此在低氧分压下的氧化有利于摩擦学应用（例如人工关节置换）的原因）。