Nanocrystalline TiB₂ coatings grown by chemical vapour deposition (CVD) are employed e.g. as hard protective coatings on cemented carbide cutting tools, owing to their high wear resistance, hardness and melting point, as well as superior thermal stability. This work applied novel cross-sectional nano-analytical techniques to investigate the effects of prolonged surface oxidation of a CVD bi-layer coating of ~3.4 μm thickness, consisting of a nanocrystalline TiB₂ protective top layer and a TiN diffusion-barrier bottom layer. Synchrotron X-ray diffraction with a nano-focussed 70 nm beam revealed cross-sectional phase compositions and residual stress gradients in the coating in as-deposited and oxidised states. Transmission electron microscopy showed a clear oxidation front, the existence of a ~400 nm thick zone of coexistence of TiB₂ and rutile TiO₂, which coincided with a marked decrease in compressive residual stress, as well as an overlying morphologically stratified TiO₂ layer. In-situ micro-cantilever experiments confirmed the structural integrity of the TiB₂ phase below the coexistence zone, where no significant oxidation-induced change in fracture stress was detected, while Young's modulus decreased by ~25%. In conclusion, the pursued nano-analytics approach revealed detailed cross-sectional correlations between oxidation-related coating disintegration, microstructure, residual stresses and mechanical properties.

由于其高耐磨性，硬度和熔点以及出色的热稳定性，通过化学气相沉积（CVD）生长的纳米晶TiB ₂涂层例如用作硬质合金切削刀具上的硬质保护涂层。这项工作应用了新颖的横截面纳米分析技术，研究了由纳米晶TiB ₂组成的〜3.4μm厚度的CVD双层涂层的长时间表面氧化作用。保护顶层和TiN扩散阻挡底层。用纳米聚焦的70 nm光束进行的同步加速器X射线衍射揭示了沉积态和氧化态的涂层中的截面相组成和残余应力梯度。透射电子显微镜显示清晰的氧化前沿，存在约400 nm厚的TiB ₂和金红石TiO ₂共存区，这与压缩残余应力显着降低以及上层的形态分层TiO ₂层相吻合。原位微悬臂梁实验证实了TiB ₂的结构完整性在共存区以下的相中，没有发现明显的氧化诱导的断裂应力变化，而杨氏模量下降了约25％。总之，所追求的纳米分析方法揭示了与氧化有关的涂层崩解，微观结构，残余应力和机械性能之间的详细横截面关系。