13th International Conference on Fracture June 16–21, 2013, Beijing, China -9- 3) The diffusion coatings become easily-deformed or induce cracks dependent on coating type and temperature. NiAl is easily deformed at 950 °C but introduces through-coating cracks at 850 °C. PtAl induces voids/cracks in or beneath the coating at both creep temperatures. Those crack initiation modes by PtAl becomes more active when increasing temperature. 4) Based on the results from microstructure analysing, the creep stress of the sample is recalculated by taking the final coating part loading-free. By such stress modification the creep test results of the coated samples are similar with those of the uncoated samples presented in the Larson-Miller diagram. It can be concluded that the applied diffusion coating has a minor influence on the overall creep behavior of the superalloy, but just consuming the effective cross section of the superalloy to carry the creep load. Acknowledgements The Siemens Industrial Turbomachinery AB (Finspang, Sweden) is greatly acknowledged for its financial support and supply of materials in this research. The Swedish Energy Agency and GKN Aerospace Engine Systems are also acknowledged for their financial support. References [1] R.C. Reed, The Superalloys Fundamentals and Applications, Cambridge, New York, 2006. [2] J.R. Nicholls, Designing oxidation-resistant coatings, JOM-J. Min. Met. Mat. S. 52 (2000) 28-35. [3] S. Osgerby, B.F. Dyson, Modelling creep properties of coated superalloys in air and aggressive environments, Mater. Sci. Eng.: A. 120–121, Part 2 (1989) 645-650. [4] H.J. Kolkman, Creep, Fatigue and Their Interaction in Coated and Uncoated Rene 80, Mater. Sci. Eng. 89 (1987) 81-91. [5] R.R. Unocic, G.B. Viswanathan, P.M. Sarosi, S. Karthikeyan, J. Li, M.J. Mills, Mechanisms of creep deformation in polycrystalline Ni-base disk superalloys, Mater. Sci. Eng.: A. 483–484 (2008) 25-32. [6] M.G. Hebsur, R.V. Miner, Stress Rupture and Creep Behavior of a Low Pressure Plasma-Sprayed NiCoCrAlY Coating Alloy in Air and Vacuum, Thin Solid Films. 147 (1987) 143-152. [7] Y. Itoh, M. Saitoh, Y. Ishiwata, Influence of high-temperature protective coatings on the mechanical properties of nickel-based superalloys, J. of Mater. Sci. (UK). 34 (1999) 3957-3966. [8] A. Sato, Y. Aoki, M. Arai, H. Harada, Effect of Aluminide Coating on Creep Properties of Ni-Base Single Crystal Superalloys, Journal of the Japan Institute of Metals. 71 (2007) 320-325. [9] J. Angenete, K. Stiller, A comparative study of two inward grown Pt modified Al diffusion coatings on a single crystal Ni base superalloy, Mater. Sci. Eng. , A. 316 (2001) 182-194. [10] J. Angenete, K. Stiller, Comparison of inward and outward grown Pt modified aluminide diffusion coatings on a Ni based single crystal superalloy, Surf. Coat. Technol. 150 (2002) 107-118. [11] N. Vialas, D. Monceau, Effect of Pt and Al content on the long-term, high temperature oxidation behavior and interdiffusion of a Pt-modified aluminide coating deposited on Ni-base superalloys, Surf. Coat. Technol. 201 (2006) 3846-3851. [12] K. Yuan, R.L. Peng, X.H. Li, L. Johansson, S. Johansson, Y.D. Wang, Analysis on
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