Abstract

PyroGenesis Inc. has developed a unique Vacuum Plasma Spraying (VPS) near-net-shape forming process for the production of multilayered free-standing components. Initial evaluation on the feasibility of applying this process for the production of gas turbine engine components has been performed. The VPS near-net-shape forming process consists of: selecting an appropriate mold material; preconditioning of mold surface ; depositing metallic, ceramic, or composite layers ; and removing mold from the spray-formed structure. The near-net-shape components are heat treated to improve their mechanical properties. A suitable heat treatment cycle was developed for the VPS-applied superalloy. Much of the recent improvements in gas turbine engine performance has been attributed to the introduction of thermal barrier coatings (TBC) for superalloy components. There exist, however, some limitations in current fabrication methods for closed hot-section components: less than ideal coating quality; welding; limited choice of superalloy material; etc... PyroGenesis has used VPS near-net-shape forming to fabricate closed components with an yttria-stabilized-zirconia inner layer, CoNiCrA1Y bond coat, and IN-738LC outer layer. The results from the initial study demonstrate the feasibility of producing near-net-shape components with good coating structures, superior superalloy materials, and the absence welds. The mold was reusable after minor surface conditioning. The TBC showed uniform thickness and microstructure with a smooth surface finish. The bond coat and structural superalloy layers were very dense with no signs of oxidation at the interface. After heat treatment, the mechanical properties of the IN-738LC compare favourably to cast materials.

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