Development of AGAT, a Third-Generation Nickel-Based Superalloy for Single Crystal Turbine Blade Applications
The new third-generation single crystal superalloy AGAT has been developed for aircraft engine turbine blade applications. Alloy design procedure is described and AGAT alloy properties are presented and compared with those of, respectively, first-, second
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Abstract
Keywords
The new third-generation single crystal superalloy AGAT has been developed for aircraft engine turbine blade applications. Alloy design procedure is described and AGAT alloy properties are presented and compared with those of, respectively, first-, second-, and third-generation AM1, CMSX-4 and CMSX-10 alloys. AGAT alloy exhibits high creep resistance at very high temperature (1200 °C) compared with first- and second-generation superalloys while maintaining moderate density (8870 kg m−3) and stable microstructure unlike the third-generation superalloy. High cycle fatigue (HCF) and low cycle fatigue (LCF) properties of AGAT alloy are similar to second-generation CMSX-4 alloy. AGAT solution heat treatment allows suppressing the c/c′ interdendritic eutectic pools at a temperature 30 °C lower than for CMSX-10 with a shorter duration. Oxidation resistance of AGAT alloy at 1150 °C is lower than that of second but higher than that of third-generation reference superalloys. AGAT shows low sensitivity to secondary reaction zone (SRZ) formation under b-NiPtAl bond coat (BC) and great spallation resistance of YPSZ EB-PVD thermal barrier coating (TBC) compared with reference alloys. Finally, single crystal turbine blades were successfully manufactured through industrial processes to be tested in engine conditions.
Nickel based Alloy design
J. Rame (&) J. Delautre J.-Y. Guedou Safran Aircraft Engines, 171 Boulevard de Valmy, 92702 Colombes, France e-mail: [email protected] P. Caron D. Locq O. Lavigne M. Perrut ONERA, DMAS, Université Paris-Saclay, 92322 Châtillon, France L. Mataveli Suave V. Jaquet A. Saboundji Safran Tech, PFX, 171 Boulevard de Valmy, 92700 Colombes, France
Single crystal Superalloy Creep Oxidation TBC
Context and Background Nickel-based superalloys are currently key materials for high temperature components of aircraft turboengines, as first stage single crystal (SC) turbine blades and vanes. During the past four decades, nickel-based SC superalloys have undergone significant chemistry changes to increase their creep resistance at high temperature. Particularly, main creep gains were successively achieved by (i) introducing rhenium up to 3 wt% in the second-generation SC superalloys, (ii) increasing the level of rhenium up to about 6 wt% in the third-generation SC superalloys, and (iii) adding ruthenium in high containing rhenium superalloys in order to stabilize their microstructure (fourth-generation SC superalloys) [1–3]. However, these compositional changes possibly led to the occurrence of microstructure instability phenomena such as cellular colonies, observed along low-angle grain boundaries and within dendrite cores, and/or secondary reaction zones (SRZ) in coated superalloys [4]. SRZ occur beneath the primary diffusion zone between the bond coat and the alloy. Their depth can grow up to hundreds of microns at service temperature due to interdiffusion phenomena. Since the mechanical strength of SRZ is significantly lower than that of the c/c′ sup
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