Nickel-based single crystal superalloys for industrial gas turbines

The oxidation resistance of four prototype single crystal nickel-based superalloys for industrial gas turbine applications is studied. All contain greater quantities of Cr than in most existing single crystal superalloys; two are alloyed with Si, one with Re. To explain the results, the factors known to influence the rate of Al\(_2\)O\(_3\) scale formation are considered. Models are developed to predict whether any given alloy composition will form a continuous Al\(_2\)O\(_3\) scale. These are used to rationalise the dependence of Al\(_2\)O\(_3\) scale formation on alloy composition in these systems. The mechanical behaviour of a new single crystal nickel-based superalloy for industrial gas turbine applications is also studied under creep and out-of-phase thermomechanical fatigue (TMF) conditions. Neutron diffraction methods and thermodynamic modelling are used to quantify the variation of the gamma prime (\(\gamma\)’) strengthening phase around the \( \gamma\)’ solvus temperature; these aid the design of primary ageing heat treatments to develop either uniform or bimodal microstructures of the \( \gamma\)’ phase. During TMF, localised shear banding occurs with the \( \gamma\)’ phase penetrated by dislocations; however during creep the dislocation activity is restricted to the matrix phase. The factors controlling TMF resistance are rationalised.EThOS - Electronic Theses Online ServiceGBUnited Kingdo