Exploration of Ternary Subsystems of Superalloys by High-Throughput Thin Film Experimentation: Optical and Electrical Da
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Exploration of Ternary Subsystems of Superalloys by High-Throughput Thin Film Experimentation: Optical and Electrical Data of the Co-Al-W System Dennis Naujoks, Dennis Koenig, Alfred Ludwig Institut für Werkstoffe, Ruhr-Universität Bochum, 44780 Bochum, Germany Abstract The complete ternary system Co-Al-W was fabricated as a thin film materials library by combinatorial magnetron sputtering. The materials library was investigated using high-throughput characterization methods such as optical measurements as well as automated resistance screening. The obtained data indicate possible phase regions and compositional regions which show early surface oxidation. The demonstrated approach illustrates that using high-throughput measurement methods provides a fast access to data of relatively unexplored materials systems. The gained data provides a valuable basis for further in-depth studies of the investigated materials systems. Introduction Combinatorial fabrication of thin film materials libraries and high-throughput characterization methods can be used for the rapid exploration of ternary systems [1, 2]. Here, the exploration of ternary subsystems of superalloys by high-throughput thin film experimentation is discussed by describing the use of high speed optical and electrical resistance analysis in order to identify regions of interest in the ternary materials system Co-Al-W. The Co-Al-W system is the most important ternary subsystem of Co-based superalloys, as in this system the γ/γ’ microstructure was identified, which is crucial for superalloys [3]. Co-based superalloys promise an increase of the achievable working temperatures in gas turbines leading to higher efficiencies. Under this perspective, the goal of the investigation of the Co-Al-W system, and further related ternary subsystems of Co-based superalloys, is to identify phase regions and eventually new ternary phases as well as TCP (Topologically Closed Packed) phases. For these investigations combinatorial fabrication and high-throughput experimentation are applied. Experimental Three ternary Co-Al-W continuous composition spread (CCS) type thin film materials libraries were deposited using a combinatorial magnetron sputter system (base pressure 10-8 mbar) (Fig.1.a)). The CCS was fabricated at room temperature by depositing a sequence of wedge-type thin films. The individual wedges with thicknesses of a few nm were realized by using moveable shutters which are positioned over the substrate holder (Fig. 1.b)). Between each deposition of a wedge, the substrate was rotated by 120°. By depositing a stack of 40 wedge layers of each element an overall thickness of 500 nm was targeted. During sputtering, the Ar (6N) pressure was 0.67 Pa and the Ar flow was set to 60 sccm. The deposition powers were set to 210 W (DC), 219 W (DC) and 156 W (DC) for Co, Al and W, respectively. Two libraries were deposited on thermally oxidized 4 in. (100) Si wafers (1.5 μm SiO2 diffusion barrier) as well as one on a 4 in. single crystalline sapphire wafer. For improving adhesion betwee
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