Modern fossil fuel energy production requires large scale machines with big size componentry. Such processes require using high temperatures and thus, chemically stable materials resistant against creep, wear, and high temperature oxidation. Manufacturing large size parts from high temperature alloys runs in many challenges related to chemical homogeneity/ phase composition stability and microstructure control to maintain in big volumes high and uniform mechanical properties, residual thermal stresses, and others. There is a necessity to develop processes to make large size components at low cost for fossil fuel energy production. It is proposed to solve this problem by building large size parts from high temperature alloys using Plasma Transferred Arc (PTA) Additive Manufacturing technique. ATS-MER possesses two PTA machines with a capability to build 4 feet x 4 feet x 17 feet components. CNC robotic manipulator will be equipped with a complete temperature/processing parameters loop to automatically adjust the processing parameters to ensure the constant/optimal pool temperature and uniformity in properties. This will also provide a possibility to accurately control grain size and to provide a fine grain microstructure in sections that require high room temperature strength, and to selectively grow grain in high temperature sections where high creep resistance is needed. To mitigate a thermal stresses issue, a special heater will be built to release stresses during deposition. In cases when large size parts require various materials in different sections (for example, to withstand creep and fatigue during operation in a turbine disk where blades are attached), it is intended to bond dissimilar materials during one stage PTA deposition. The mechanical properties of PTA deposited alloy 718 will be investigated and compared with those for commercially available alloy 718. The PTA technology to make large size tie-bolts and turbine disks will be developed. A disk for a real gas turbine and a tie-bolt will be produced by PTA, machined, heat treated and delivered to DOE. The technology to apply a dissimilar high temperature alloy on the periphery of 718 disk will be developed. The microstructures and mechanical properties of the deposited materials will be investigated.
