GOALI: Stability of Ni-Based Superalloy Single Crystals

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This GOALI program teams the University of Florida and Pratt & Whitney Corp., with additional inputs from the NASA-Glenn Research Center and NIST, to develop a scientific database for the phase equilibria and mechanical behavior of both model and commercial nickel-base single crystals. This microstructural stability database will build upon the NIST database created for solidification of Ni-base alloys. The improved database will allow material engineers to know more accurately which alloys are prone to the deleterious topological close packed (TCP) phase and how its formation affects the mechanical properties of in-service components. Simple empirical statistical models exist to predict TCP phases in simple compositions, but the models have poor predictive accuracy in complex alloys. A more accurate model based on firm metallurgical principles is needed to predict microstructural stability as a function of alloy composition and temperature ranges. The improved database can ultimately be used to optimize existing alloys to more stable compositions, assess sensitivity to alloy segregation, and define optimum thermo-mechanical processing windows. P&W provides support for the graduate students and the PI for extended visits to the P&W facility each year of the program to conduct in-house experiments. The students will interact with the program advisors and contribute to electronic status reports and annual program review. The project is supported by the MPS Office of Multidisciplinary Activities and the DMR Metals Research Program.%%%The need to achieve greater performance, higher efficiency, and reduced emissions has resulted in higher turbine inlet temperatures. A most critical component in the turbine section is the turbine blade, which experiences high temperature, high stress, high-cycle fatigue, and a corrosive environment. Single crystal Ni-base superalloys were developed to meet the extreme service requirements in the turbine section. The high temperatures typically encountered by turbine blades and vanes can result in the potential for both microstructural and mechanical property changes. ***