Processing Studies of High Temperature Ni Based Superalloys by Electron Beam and Laser Powder Bed Fusion

Additive Manufacturing (AM) offers enormous potential for cost savings and lead time reduction for aerospace parts. The anticipated cost savings is expected to be on the order of $100M when considering the wide range of hot section components in future military and civil aircrafts planned for production in the next 30 years. Under the USAF sponsored Metals Affordability Initiative, Rolls-Royce Corporation led a team including members from Honeywell, PCC/Timet, Carpenter Technology, Arconic , University of Tennessee, and Oak Ridge National Laboratory to assess the feasibility of producing crack free microstructures in a high temperature nickel superalloy using laser and electron beam powder bed fusion. Multiple artifact designs, capturing key features in candidate components, were considered in order to assess the limitations of each AM process for producing accurate geometric features and acceptable microstructures. Detailed metallurgical assessments, dimensional measurements, and X-ray CT were completed of select geometric features of interest. The extent of bulk and near surface cracks was evaluated. By using a systematic DOE approach, the team was able to show a reduction in feature cracking propensity through AM process parameter and HIP cycle optimization trials for both laser (LPBF) and electron beam (EBPBF) powder bed fusion. Although HIP was shown to be beneficial in reducing the extent of cracking, some internal micro cracks and surface breaking cracks could not be totally eliminated. AM process parameters, component geometry, and post processing methods must be simultaneously optimized to successfully achieve flight quality components.