Effect of Build Orientation and Post Processing of a Direct Laser Deposited Nickel Superalloy as Determined by the Small Punch Creep Test

Abstract

Direct Laser Deposition (DLD) is a modern Additive Layer Manufacturing (ALM) technology that offers the possibility of lean manufacture and the ability to produce near-net shape components with complex geometries. Anisotropic microstructures are typically produced due to thermal cycles that occur during the layer by layer process, resulting in epitaxial grains forming along the build direction. Therefore, build direction, whether horizontal (0°) or vertical (90°), may have a pronounced effect upon mechanical properties. While, it is generally accepted that the mechanical properties of cast materials are well understood, the same cannot be said for materials produced using DLD. Although, mechanical testing of materials usually dictates the use of round bar specimens, due to the cost of manufacture and fundamental nature of this study a miniaturised test technique better lends itself to characterise the cast and DLD built alloys’ properties. The Small Punch (SP) creep test is a widely utilised miniaturised test technique for characterising and ranking the creep response of metallic material properties when large quantities may not be readily available. This paper will apply the SP creep test to characterise the properties of DLD variants of the nickel based superalloy C263 in comparison to the traditional cast material. Tests were performed at elevated temperatures akin to those experienced in service. Interpretation of the microstructures and SP creep results has been carried out; relating build direction, microstructures, minimum displacement rate and time to rupture.