SupREme

Ni-based superalloys possess an excellent combination of mechanical properties and environmental resistance at elevated temperatures. However, grain boundaries of the superalloys are always a source of weakness due to their interaction with gaseous environments. Moreover, these alloys exhibit sensitivity to dwell times (time period at peak loads) differently depending on the loads and environment. These problems are of particular concern when considering the application of Ni-based superalloys in the hot sections of aero and land-based gas turbines, in which the components are exposed to high temperature corrosive gas streams whilst under high stresses for a long time. Furthermore, operating temperatures are rising markedly due to ongoing fuel efficiency demands and the need to reduce greenhouse gas emissions; hence, failure resulted from so-called “environmentally-assisted cracking (EAC)” is becoming prevalent and is now one of the major limitations to the application of Ni-based superalloys at elevated temperatures. The precise mechanism of EAC is contentious, necessitating systematic experimentation and associated characterization at the appropriate length scale to elucidate the underlying physical and chemical factors at play. Powder-bed fusion additive manufacturing (PBFAM) techniques including selective laser melting (SLM) and electron beam melting (EBM) can be used to fabricate Ni-based superalloys, with the possibility to tailor the microstructure and reduce the risk of EAC, which can be extremely attractive for the gas turbine manufacturers. Therefore, the successive efforts to find a superior resistance to EAC using AM techniques motivate SupREme. The overall goal of SupREme is to elaborate the current understanding of cracking behavior of load-bearing EBM/SLM-manufactured Ni-based superalloys exposed to high temperature corrosive environments. The main focus will be to design a proper microstructure that can reduce the risk of EAC in the AM components