The effect of corrosive environment on the crack growth behaviour of nickel based superalloys

The operation of nickel-base superalloys in gas turbine engines exposes the components to a broad range of conditions ranging across temperature, stress, time and environment. Furthermore, the gaseous environment, in combination with the high temperatures of operation, can lead to the formation of corrosive species, which can attack the component and lead to degradation during service. One key aspect of component material behaviour is the understanding of the propagation rates of fatigue cracks in the material, which is conventionally conducted in air. However, the impact of corrosive species on crack propagation rates is far less well understood. Utilising the specialist testing chambers available at the Institute of Structural Materials, Swansea University, this study will seek to investigate the role of corrosive environments on the crack propagation rates of a modern nickel-base superalloy. The study will seek to understand the effect of different loading waveforms and cycles in order to determine the impact of corrosion damage on fatigue crack propagation rates. Following testing, detailed characterisation of the fracture surfaces and corrosive species formed during testing will be necessary to inform the operative mechanisms and provide insights into the critical aspects of corrosion crack growth behaviour.