Degradation and protection phenomena of high-alloy Fe-Cr alloys in hot, multi-component gas systems

本课题旨在对高合金Fe-Cr合金在SO2、H2O和含氯沉积物（KCl）下的高温气体环境中的损伤机理进行基础研究。这些材料在各种燃烧电厂中用作热交换器管的材料。生物质和生物质共烧电厂中使用的材料的烟气侧损坏是一个严重的问题，并限制了此类电厂的运行温度。腐蚀产物的结晶和生长的基本方面将在降解的早期阶段通过时间依赖老化实验进行研究。高纯度模型合金（Fe-Cr）和模型气体成分将用于关注元素Fe， Cr， S和Cl的反应。采用广谱的经典显微镜技术和先进的表征方法，如x射线近边缘结构吸收光谱（XANES），对形成的腐蚀区域进行定性和定量相分析。经典显微镜与XANES的结合导致对现有反应产物的极其精确的验证。这种方法应该有助于显示金属离子和气体组分在反应产物晶体结构上的扩散和传输路径。在特殊设计的光反应器中，通过原位能量色散x射线衍射直接跟踪反应过程中腐蚀极早期阶段的结晶和生长。该项目旨在解决三个问题。第一个目标是研究保护性Cr2O3的形成。为此目的，使用一种实验装置，使材料暴露在热烟气中。首先，对三种不同的高合金（Cr>15Ma%）模型合金进行了时效试验，反应时间为12h

The proposed project aims at the fundamental investigation of the damage mechanisms of high-alloyed Fe-Cr alloys in a hot gas atmosphere under SO2 and H2O and under chlorine-containing deposits (KCl). These materials are used as materials for heat exchanger tubes in various combustion power plants. The damage to the flue gas side of the materials used in biomass and biomass co-fired power plants is a serious problem and limits the operating temperature of such plants. Fundamental aspects of crystallization and growth of corrosion products will be investigated at an early stage of degradation by means of time-dependent ageing experiments. High purity model alloys (Fe-Cr) and model gas compositions are to be used to focus on the reaction of the elements Fe, Cr, S and Cl involved. The qualitative and quantitative phase analysis of the formed corrosion zones is performed using a broad spectrum of classical microscopy techniques and advanced characterization methods, such as X-ray near-edge structure absorption spectroscopy (XANES). The combination of classical microscopy with XANES leads to an extremely precise verification of the existing reaction products. This approach should help to show diffusion and transport paths of metal ions and gas components over the crystal structure of the reaction products. Crystallization and growth at a very early stage of corrosion will be followed directly during the reaction by in-situ energy dispersive X-ray diffraction in a specially designed light reactor.The project aims at three questions. The first objective is to investigate the formation of protective Cr2O3. For this purpose, an experimental setup is used that allows materials to be exposed to a hot flue gas. First, ageing tests are carried out on three different high-alloyed (Cr>15Ma%) model alloys with reaction times 12h