Active oxidation protection coatings for Mo-Si-B high temperature materials

由于效率的提高，高温稳定材料Mo-Si-B作为燃气轮机的替代材料得到了广泛的研究。在这种材料体系中尚未解决的一个问题是它的氧化行为：Mo组分以Mo(IV)氧化物的形式显示出讨厌的形式。固有的材料保护机制--近表面Si和B的氧化及其反应形成氧扩散限制玻璃层--是不够的。本工作的目的是开发一种新型、活性的多层环境屏障涂料，其初始保护玻璃层在低温(500°C至800°C)下形成，在使用条件下(1100°C至1200°C)具有高捕氧能力和氧扩散抑制层。这些涂层是基于填充了不同颗粒大小和体积分数的颗粒硅、硼、钛和/或铝的聚硅氮烷，它将通过浸渍Mo-Si-B衬底材料来应用，然后进行热处理，以转化为活性陶瓷材料(层调节)，并在类似服务条件下进行热处理。在类似服务条件下的条件和处理之后，将执行固态样品表征的标准方法。XPS研究将更深入地了解保护层的形成机理，纳米压痕实验将有助于表征和了解保护层的机械性能。结果将用于模型开发，以了解物理化学层的形成及其在使用条件下的功能。这将有助于转移Mo-Si-B耐火合金以外的保护层的发展。

Due to an increase in efficiency, the high-temperature stabile material Mo-Si-B is intensely investigated as a substitute material in combustion turbines. A problem not solved yet in this material system is its oxidation behavior: the Mo component shows pesting in form of Mo(IV) oxid formation. The intrinsic material protection mechanism– the oxidation of near-surface Si and B and its reaction to form an oxygen diffusion limiting glass layer – is insufficient. Aim of this work is to develop a novel-type, active multi-layer environmental barrier coating with an initial protective glass layer formation at low temperatures (500 °C to 800 °C), and a high oxygen-trapping capacity and oxygen diffusion inhibition layer under service conditions (1100 °C to 1200 °C). These layers are based on a perhydropolysilazane filled with particulate Si-, B-, Ti and/or Al-containing components of variable particle size and volume fraction, and it will be applied by dip coating of Mo-Si-B substrate materials followed by heat treatment for the conversion into an active ceramic material (layer conditioning) and heat treatment under service-like conditions. Standard methods will be carried out for solid-state sample characterization after conditioning and treatment under service-like conditions. XPS investigations will give a deeper insight into protective-layer formation mechanisms and nanoindentation experiments allow to characterize and to understand the layers´ mechanical properties. The results will be used for models development to understand the physicochemical layer formation and their function under service conditions. This will help to transfer the development of protective layers for other than Mo-Si-B refractory based alloys.