TIALMET - Surface modification of gamma-TiAl alloys and its influence on mechanical properties and phenomena under high temperature conditions

该项目的目的是获得关于表面改性对γ -钛铝化物的微观结构、抗氧化性和机械性能影响的新的和详细的知识。在该项目中，合作伙伴将密切合作开发几种表面改性，(i)通过化学气相沉积（CVD）和物理气相沉积（PVD）两种不同的方法沉积保护性AlSi和TiAlCrY涂层，（ii）在不同的氧分压下通过预氧化进行额外的表面改性，以促进形成稳定的无tio2保护层（α -氧化铝）。（iii）喷丸处理，在表面引入压应力，以改善TiAl合金的机械（疲劳）性能。该项目的一个新颖之处是通过CVD和PVD沉积AlSi涂层并将其作为tbc的粘结涂层。AlSi和TiAlCrY涂层在γ - tial合金上形成缓慢生长和稳定的α -氧化铝结垢的能力，为它们在TBC体系中的应用创造了潜力，在TBC体系中，7YSZ面漆和粘结层之间的结合和相容性非常重要。然而，关于这种TBC体系中界面现象及其演变的数据，以及这些保护涂层对基体合金力学性能的影响都是缺失的。对表面改性的基本分析，如在各种环境条件下依赖于保护性氧化铝鳞片生长的预氧化，以及通过喷丸强化的机械处理，将导致具有改进性能的改性表面，并通过新技术进行评估，例如在大幅减少样品数量的情况下测定脆性到韧性的转变。该项目旨在首次给出不同温度下表面改性对TiAl的氧化和疲劳性能影响的系统结果。此外，引入压应力目标以提高疲劳寿命，这是以前从未尝试过的γ - tial合金涂层。所有目标只有通过波兰和德国伙伴之间的密切合作才能实现，因为子任务、使用的表面改性方法和测试依赖于彼此的工作，没有这种国际合作就无法进行。

The aim of the project is to obtain new and detailed knowledge about the influence of surface modifications on microstructure, oxidation resistance and mechanical properties of gamma-titanium aluminides. Within the project several surface modifications will be developed in close coop-eration by the partners, (i) deposition of protective AlSi and TiAlCrY coatings by two different methods, chemical vapor deposition (CVD) and physical vapor deposition (PVD), (ii) an additional surface modification by pre-oxidation under varying partial pressures of oxygen to foster the formation of a stable and TiO2-free protective scale (alpha-alumina), and (iii) shot peen-ing to introduce compressive stresses into the surfaces to improve the mechanical (fatigue) properties of the TiAl alloy. One novelty of the project is the deposition of AlSi coatings by CVD and PVD and its applica-tion as bond coats for TBCs. The ability of AlSi as well as TiAlCrY coatings to form a slow-growing and stable alpha-alumina scale on gamma-TiAl alloys creates a potential for their application in TBC systems where bonding and compatibility between the 7YSZ topcoat and bond coat is of great importance. However, data on interfacial phenomena and their evolution in such TBC systems, and the influence of these protective coatings on mechanical properties of the base alloy are missing. Fundamental analyses of surface modifications such as pre-oxidation relying on the growth of a protective alumina scale under various environmental conditions as well as mechanical treatments by shot peening will lead to modified surfaces with improved properties, evaluated by new techniques such as determination of the brittle to ductile transition with drastically reduced sample numbers.The project aims to give for the first time systematic results on the influence of surface modi-fications on the oxidation and fatigue properties of TiAl at different temperatures. Moreover, introduction of compressive stresses targets to improve the fatigue life, which was never tried before for coatings on gamma-TiAl alloys. All goals can only be achieved by close collaboration between the Polish and German partners, since the sub-tasks, surface modification methods used, and tests rely on the work from each other and could not be performed without this international collaboration.