Abstract
A family of novel polycrystalline Ni-based superalloys with varying Ti:Nb ratios has been created using computational alloy design techniques, and subsequently characterized using atom probe tomography and electron microscopy. Phase chemistry, elemental partitioning, and γ′ character have been analyzed and compared with thermodynamic predictions created using Thermo-Calc. Phase compositions and γ′ volume fraction were found to compare favorably with the thermodynamically predicted values, while predicted partitioning behavior for Ti, Nb, Cr, and Co tended to overestimate γ′ preference over the γ matrix, often with opposing trends vs Nb concentration.
Highlights
NICKEL-BASED superalloys are widely used in the high-pressure section of gas turbine engines due to their exceptional oxidation resistance and strength at temperatures up to and exceeding 1000 °C.[1,2] Commercial and environmental drivers seek to increase turbine operating temperatures, requiring further alloy optimization in order to satisfy the increasing demands on strength and oxidation resistance
The target alloy compositions[27] given in Table I result from using the ABD method to predict compositions with high strength at 800 °C combined with good oxidation resistance
The as-manufactured alloy compositions are provided in Table I, which were measured using a combination of X-ray fluorescence (XRF) spectroscopy, the combustion infra-red method and inductively coupled plasma—optical emission spectroscopy (ICP-OES)
Summary
NICKEL-BASED superalloys are widely used in the high-pressure section of gas turbine engines due to their exceptional oxidation resistance and strength at temperatures up to and exceeding 1000 °C.[1,2] Commercial and environmental drivers seek to increase turbine operating temperatures, requiring further alloy optimization in order to satisfy the increasing demands on strength and oxidation resistance. This deformation mechanism is heavily influenced by c¢ volume fraction and chemistry, as c¢ forming elements such as Ti, Ta, and Nb have been shown to increase strength by raising the stacking fault energy at anti-phase boundaries (APB) found in the ordered precipitates.[6,7] there are limits regarding the addition of c¢ forming elements, as high
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