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工艺的效率，高温条件越来越苛刻，这就对镍基合金等金属结构材料提出了越来越高的要求。在氢气生产的高温过程中，如以前从化学和石化工业中所知的，具有还原性、富碳气氛的高温过程正变得越来越重要。在这些过程中，由于金属粉尘的高温腐蚀形式，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尘的攻击机理及其动力学。铜合金化已被证明可以减少金属粉尘的侵袭，但其潜在的机制，特别是其影响因素尚不清楚。为了证实、反驳或扩展现有的理论，研究了Cu含量以及2 wt.% Mn、Fe、Ti、Nb、Mo、Si或Cr和4 wt.% Al的含量对合金抗金属粉尘性能的影响，这些氧化物都是形成热力学稳定的氧化物。为此，铸造二元、三元和四元成分的单晶模型合金。在两种不同的气氛（含和不含酒精）中测试了它们对金属粉尘的抵抗力，并将其与气体成分的热力学稳定性联系起来。热重分析也允许比较四元含铝合金，形成保护氧化层，和他们的三元对应物，只包含Cu作为保护合金元素。这些基础研究用于有针对性地开发用于现有和新应用的金属防尘材料，例如在工艺气体中增加醇的比例。

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.