Nickel aluminides: a step toward industrial application

Intermetallics based on nickel aluminide are subjects of an ongoing development of new high-temperature materials for application as heat shields for combustion chambers and as first-row vanes in industrial gas turbines. Due to the complex geometry of these parts and the complicated machinability of NiAl intermetallics, these components have to be manufactured by near-net-shape casting. This casting technique required an adaptation of the investment casting process to the special properties of NiAl alloys. For this purpose, a special ceramic mold system was developed to prevent casting defects and excessive mold–metal reactions. Suitable casting parameters were established for the production of grain-refined, crack-free heat shields. Accompanying numerical simulations were performed to optimize the investment casting process for the NiAl-alloy helped to save development time and to reduce the number of casting trials noticeably. These modeling results for various casting conditions (mold and pouring temperature, cooling rate) were compared with outcomes of casting trials in aspects of porosity, mold filling and temperature-field development during the casting process.