Thermochemical modelling of the phase stability of coatings deposited from the gas phase

(Ti1-xAlx)N涂层因其在高温下的耐磨性而被广泛用于例如刀具应用。不同作者报道，在(Ti1-xAlx)N系统中，具有良好摩擦学性能的亚稳立方相向涂层性能较差的亚稳六方相的转变发生在0，4×0，91范围内。六方相出现的临界铝浓度变化如此之大的原因并不明显。该项目的目的是为了帮助理解这种相当大的变化的原因。我们试图扩展现有的热化学模型，基于比较化学计量比和无缺陷的单个结构的吉布斯能量，以包括化学计量比的变化以及晶界的存在。因此，我们建议系统地研究薄膜化学计量比、晶粒度和形成的结构(立方体和/或六边形)之间的关系。我们预计，该模型将有助于更好地基本理解上述不同临界铝浓度报告的原因。此外，这样的模型将能够预测涂层成分。与通常采用的试错法相比，这将是从气相生产涂层方面的重大进步。

(Ti1-xAlx)N coatings are widely used for e.g. cutting toolapplications on account of their wear resistance at elevatedtemperatures. In the system (Ti1-xAlx)N, the transformationfrom the metastable cubic phase, with excellent tribologicalproperties, to the metastable hexagonal phase, with inferiorcoating properties, occurs in a range of 0,4 x 0,91, asreported by different authors. The reasons for the ratherextensive variation in the critical aluminium concentration atwhich the hexagonal phase appears are not evident.The aim of the proposed project is to contribute towardsunderstanding the reasons for this rather exensive variation.We seek to expand an existing thermochemical model, based oncomparing the Gibbs energy of stoichiometric and defect freeindividual structures to include variations in stoichiometry aswell as the presence of grain boundaries.Hence, we suggest to systematically, investigate therelationship between film stoichiometry, grain size and thestructure formed (cubic and/or hexagonal). We anticipate thatthis model will contribute significantly to a better basicunderstanding of the reasons for the above discussed differentcritical aluminium concentrations reported. In addition, such amodel will enable prediction of the coating constitution. Thiswould represent significant progress significant progress forthe production of coatings from the gas phase as compared tothe usually applied trial and error methods.