Metal dusting of Ni-Cu alloys: Dependence of high-temperature attack on crystal orientation and small amounts of thermodynamically stable oxide formers

为了进一步提高高温加工的效率，条件越来越苛刻，对镍基合金等金属结构材料提出了越来越高的要求。在生产氢气的高温过程中，具有还原、富碳气氛的高温过程，如以前从化工和石化行业所知的那样，正变得越来越重要。在这些过程中，由于金属粉尘具有侵略性的高温腐蚀形式，材料会发生降解。本课题从表面取向、合金成分和工艺气氛变化等方面研究了镍铜合金金属粉化的侵蚀机理及其动力学。铜的合金化可以减少金属粉尘的侵蚀，但其机理，特别是其影响因素尚不清楚。为了证实、驳斥或扩展已有的理论，研究了铜含量和2wt%的Mn、Fe、Ti、Nb、Mo、Si或Cr以及4wt%Al等热力学稳定氧化物的含量对合金抗金属粉尘性能的影响。为此，铸造了具有二元、三元和四元组成的单晶模型合金。在两种不同的气氛中(有无醇)测试了它们对金属粉尘的耐受性，并与气体成分的热力学稳定性联系在一起。热重分析还可以比较形成保护氧化层的四元含铝合金和只包含铜作为保护合金元素的三元合金。这些基础研究被用于有针对性地开发既有的和新的应用中的抗金属粉尘材料，例如增加工艺气体中的醇比例。

In order to further increase the efficiency of high-temperature processes, the conditions are becoming more and more aggressive, which places ever higher demands on the metallic structural materials such as Ni-based alloys. In the case of H 2 production high temperature processes high-temperature processes with reducing, carbon-rich atmospheres, as previously known from the chemical and petrochemical industry, are becoming increasingly relevant. In these processes, material degradation occurs due to the aggressive high-temperature corrosion form of metal dusting. In this project the attack mechanism of the metal dusting of Ni-Cu alloys and its kinetics are investigated with respect to the surface orientation, the alloy composition, and the variation of the process atmosphere. Alloying with Cu has been shown to reduce metal dusting attack, but the underlying mechanism and in particular its influencing factors are still unclear. To confirm, refute or extend existing theories, the influence of the Cu content and that of 2 wt.% Mn, Fe, Ti, Nb, Mo, Si or Cr and 4 wt.% Al, all of which form thermodynamically stable oxides, on the metal dusting resistance of the alloys is investigated. For this purpose, single-crystal model alloys with binary, ternary, and quaternary compositions are cast. Their resistance towards metal dusting is tested in two different atmospheres (with and without alcohols) and linked to the thermodynamic stability of the gas compositions. Thermogravimetric analysis also allows comparison between quaternary Al-containing alloys, which form protective oxide layers, and their ternary counterpart, which contains only Cu as the protective alloying element. These fundamental investigations are used for the targeted development of metal dusting-resistant materials for both established and new applications, e.g. with increased proportions of alcohols in the process gas.