High Temperature Failure and Microstructural Investigation of Additive Manufactured Rene 41

Abstract In developing a wire-arc direct energy deposition process for creep resistant alloys used in high-speed flight applications, structures were built from nickel-based superalloy Rene 41. Samples of AM material were analysed for their microstructural and mechanical properties, in both as deposited (AD) and heat-treated (HT) conditions. Tensile specimens were tested at room-temperature, 538, 760, and 1000 °C. Macroscopically, large columnar grains made up of a typical dendritic structure were observed. Microscopically, significant segregation of heavier elements, grain boundary precipitates, and secondary phases were observed, with key differences observed in HT material. There was a clear distinction between failure modes at different testing temperatures and between AD and HT variants. A fractographic investigation found a progressive move from brittle to ductile fracture with increasing testing temperature in both AD and HT conditions, as well as microstructural features which support this observation.