Thermodynamic investigations of the diffusion-based and oxidation-based depletion mechanisms in MCrAlY coatings

如今，现代燃气涡轮机供应商在开发、制造和服务领域已经面临着不断加剧的成本压力，这是由于它们之间以及与替代能源的广泛经济竞争。提高进入涡轮机的入口温度或延长部件的使用寿命是提高燃气涡轮机设施的效率和收益率的既定方法。为了保护部件免受氧化和腐蚀的增加的风险，涡轮机的热气路径中的部件例如用MCrAlY（M= Ni和/或Co）覆盖涂层屏蔽。使MCrAlY涂层适应现代燃气涡轮机设施越来越多的操作条件是确保每个部件和涡轮机最大使用寿命的必要条件。直到今天，一般的加工路线仍然是在试验和错误的基础上调整化学成分和性质。然而，这是一个耗费时间和成本的过程，因为每一个潜在的系统都必须在以后进行验证和现场测试。经验表明，现代热力学软件包是一个强大的预测性能和结构的材料和合金通过计算系统相关的状态变量和模拟扩散过程。然而，目前这些程序只能模拟固相和/或液相之间的扩散。由于氧和相关氧化物（例如Al 2 O3、Cr2 O3、Y2 O3）的迁移率数据库（商业）不可用，因此不可能直接考虑大气影响。然而，扩散控制的氧化皮的形成和生长与邻近表面接近耗尽，对于涂层和整个部件的寿命至关重要。该研究项目致力于研究与IN 738 LC一起使用的众所周知的γ/β MCrAlY覆盖涂层的回火相关氧化和互扩散过程。在此数据的基础上，应开发模拟模型，并随后通过氧化试验、长期热处理（12000 h）、微观研究、EDX、XRD以及可用文献数据进行验证。与以前的研究相比，应根据确定的寿命标准和模拟结果进行寿命预测。假设一个成功的验证的伽马/β MCrAlY模拟模型，应用到化学和微观结构不同的伽马/伽马总理MCrAlY覆盖系统计划在潜在的第四个供资年度。分析所开发模型的通用性、可靠性和适应性。

Already today modern gas turbine suppliers are confronted with a steadily intensifying cost pressure in the development, manufacturing and service areas due to extensive economic competition among themselves and with alternative energy sources. Increasing the inlet temperatures into the turbine or extending the service life of components are established methods to increase the efficiency and profitability of gas turbine facilities. In order to protect parts from increased risk of oxidation and corrosion components in the hot gas path of a turbine are shielded for example with MCrAlY (M= Ni and/or Co) overlay coatings. Adapting MCrAlY coatings onto the more and more versatile operation conditions of modern gas turbine facilities is a necessity to ensure maximum service life of each part and the turbine. Still today the general processing route is to adapt the chemical composition and properties on an experimental trial and error basis. This, however, is a time and cost consuming process, because every single potential system has to be validated and field tested later. Experience has shown that modern thermodynamic software packages are a powerful to predict properties and structure of materials and alloys through calculation of system related state variables and simulation of diffusion processes. At the present point in time these programs can only simulate diffusion between solid and/or liquid phases, though. A straightforward consideration of the atmospheric influence is not possible due to (commercial) unavailability of mobility databases for oxygen and relevant oxides (e.g. Al2O3, Cr2O3, Y2O3). The diffusion controlled formation and growth of an oxide scale with adjacent surface near depletion, however, is crucial for the lifetime of the coating and the whole part. The research project is dedicated to investigate the tempering related oxidation and interdiffusion processes for a well known gamma/beta MCrAlY overlay coating in conjunction with IN738LC. On the basis of this data, a simulation model shall be developed and subsequently validated through oxidation trails, long-term heat treatments (12000 h), microscopic investigations, EDX, XRD, as well as available literature data. Compared to previous studies a lifetime prediction shall be given based on identified lifetime criteria and simulation results. Presuming a successful validation of the gamma/beta MCrAlY simulation model, the application onto a chemical and microstructurally different gamma/gamm prime MCrAlY overlay system is planned in a potential fourth funding year. By doing so, the universality, reliability and adaptability of the developed model shall be analysed.