Abstract

Many of the recent improvements in gas turbine engines have been attributed to the introduction of thermal barrier coatings (TBC) for superalloy components. There exists, however, some limitations in current fabrication methods for closed hot-section components: less than ideal coating quality, the need for welding, and limited choice of superalloy material. This paper describes a vacuum plasma near-net-shape process that overcomes these limitations. The process is used to fabricate closed components from yttria-stabilized-zirconia with a CoNiCrAlY bond coat and IN-738LC outer layer. The results from the study show that it is possible to produce near-net-shape superalloy parts with good coating properties and the absence of welds. The mold was reusable after minor reconditioning and the coatings were uniform in 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 favorably to cast materials.

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