ADDITIVE MANUFACTURING OF HOT GAS PATH PARTS AND ENGINE VALIDATION IN A HEAVY DUTY GT

Additive manufacturing and in particular Selective Laser Melting (SLM) are manufacturing technologies that can become a game changer for the production of future high performance hot gas path parts. SLM radically changes the design process giving unprecedented freedom of design and enabling a step change in part performance. Benefits are manifold, such as reduced cooling air consumption through more efficient cooling schemes, reduced emissions through better mixing in the combustion process and reduced cost through integrated part design. GE is already making use of SLM for its gas turbine components based on sound experience for new part production and reconditioning. The paper focuses on: a) Generic advantages of rapid manufacturing and design considerations for hot gas path parts b) Qualification of processes and additive manufacturing of engine ready parts c) SLM material considerations and properties validation d) Installation and validation in a heavy duty GT Additive Manufacturing (AM) of hot gas path components differs significantly from known process chains. All elements of this novel manufacturing route had to be established and validated. This starts with the selection of the powder alloy used for the SLM production and the determination of essential static and cyclic material properties. SLM specific design features and built-in functionality allow to simplify part assembly and to shortcut manufacturing steps. In addition, the post-SLM machining steps for engine ready parts will be described. As SLM is a novel manufacturing route, complementary quality tools are required to ensure part integrity. Powerful nondestructive methods, like 3D scanning and X-ray computer tomography have been used for that purpose. GE's engine validation of SLM made parts in a heavy duty GT was done with selected hot gas path components in a rainbow arrangement including turbine blades with SLM tip caps. Although SLM has major differences to conventional manufacturing the various challenges from design to engine ready parts have been successfully mastered. This has been confirmed after the completion of the test campaign in 2015. All disassembled SLM components were found in excellent condition. Subsequent assessments of the SLM parts including metallurgical investigations have confirmed the good part condition.