Structure of NiCrAlY Coatings Deposited on Oriented Single Crystal Superalloy Substrates by Laser Cladding

Article Preview

Abstract:

In the present work single and multiple layer NiCrAlY coatings were produced by laser cladding on (100) single-crystalline substrates of SRR99 Ni-based superalloy. Detailed structural characterisation and texture analysis by optical microscopy, scanning electron microscopy, X-ray diffraction and Rutherford backscattering showed that the NiCrAlY coatings consisted essentially of gamma phase with yttrium oxide (Y2O3) and a small proportion of yttrium–aluminium garnet (Al5Y3O12) precipitated in the interdendritic regions. The coatings presented a columnar dendritic structure grown by epitaxial solidification on the substrate and inherited the single-crystalline nature and the orientation of the substrate. The coating material also showed a mosaicity and a defect density similar to those of the substrate. It can be expected that the protective effect of these coatings against oxidation is greatly enhanced compared with polycrystalline coatings because high diffusivity paths, such as grain boundaries, are eliminated in single-crystalline coatings, thus reducing mass transport through the coating.

You might also be interested in these eBooks

Info:

Periodical:

Pages:

503-508

Citation:

Online since:

July 2011

Export:

[1] Versnyder, F.L. and M.E. Shank, Development of Columnar Grain and Single Crystal High Temperature Materials through Directional Solidification. Materials Science and Engineering, 1970. 6(4): pp.213-247.

DOI: 10.1016/0025-5416(70)90050-9

Google Scholar

[2] McLean, M., Directionally Solidified Materials for High Temperature Service. 1983, London: The Metals Society.

Google Scholar

[3] D'Souza, N., et al., Directional and single-crystal solidification of Ni-base superalloys: Part I. The role of curved isotherms on grain selection. Metallurgical and Materials Transactions A-Physical Metallurgy and Materials Science, 2000. 31(11): pp.2877-2886.

DOI: 10.1007/bf02830351

Google Scholar

[4] Han, Y.F., Z.P. Xing, and M.C. Chaurvedi, Structural Intermetallics. The Minerals, Metals and Materials Society, ed. M.V. Nathal, et al. (1997).

Google Scholar

[5] Reed, R.C., The Superalloys, Fundamentals and Applications. first ed. Cambridge University Press. 2006: Cambridge University Press. 372.

Google Scholar

[6] Sprague, J.A. and J.L. Cocking, M-Cr-Al-X Coatings for Superalloys, in Advances in High Temperature Structural Materials and Protective Coatings, A.K. Koul, et al., Editors. 1994, National Research Council of Canada: Ottawa. pp.205-225.

Google Scholar

[7] Brandl, W., et al., The oxidation behaviour of sprayed MCrAlY coatings. Surface & Coatings Technology, 1996. 87-8(1-3): pp.41-47.

DOI: 10.1016/s0257-8972(96)03039-3

Google Scholar

[8] Brandl, W., et al., The oxidation behaviour of HVOF thermal-sprayed MCrAlY coatings. Surface & Coatings Technology, 1997. 94-5(1-3): pp.21-26.

DOI: 10.1016/s0257-8972(97)00470-2

Google Scholar

[9] Damborenea, J. d. and A.J. Vazquez, Laser Cladding of High-Temperature Coatings. Journal of Materials Science, 1993. 28: pp.4775-4780.

DOI: 10.1007/bf00414271

Google Scholar

[10] Vilar, R., Laser cladding. Journal of Laser Applications, 1999. 11(Special number: Laser Applications Around the World, Invited Reviews from Amongst The World's Leaders, Part 2): pp.64-79.

Google Scholar

[11] Ribaudo, C.R., J. Mazumder, and D.W. Hetzner, Laser-Clad NiAlCrHf Alloys with Improved Alumina Scale Retention. Metallurgical Transactions B, 1992. 23(4): pp.513-522.

DOI: 10.1007/bf02649670

Google Scholar

[12] Gaümann, M., et al., Epitaxial laser metal forming : analysis of microstructure formation. Mater. Sci. Eng. A, 1999. 271: pp.232-241.

Google Scholar

[13] Gaümann, M., et al., Epitaxial Laser Metal Forming on a single Crystal Superalloy, in Laser Assisted Net shape Engineering 2, Proceedings of the LANE'97, M. Geiger and F. Vollertsen, Editors. 1997, Meisenbach: Bamberg. pp.651-657.

Google Scholar

[14] Walton, D. and B. Chalmers, The Origin of the Preferred Orientation in the Columnar Zone of Ingots. Transactions of the American Institute of Mining and Metallurgical Engineers, 1959. 215(3): pp.447-457.

Google Scholar

[15] Lee, D.N., et al., Factors determining crystal orientation of dendritic growth during solidification. Materials Chemistry and Physics, 1997. 47(2-3): pp.154-158.

DOI: 10.1016/s0254-0584(97)80044-2

Google Scholar

[16] Gaümann, M., et al., Single-Crystal Laser Deposition of Superalloys: Processing-Microstructure Maps. Acta Materialia, 2001. 49: pp.1051-1062.

DOI: 10.1016/s1359-6454(00)00367-0

Google Scholar

[17] Mokadem, S., et al. Microstructure control during single crystal welding and deposition of Ni-base superalloys. in TMS annual meeting 2004. 2004. Charlotte, USA.

Google Scholar

[18] Franco, N., S. Pereira, and A.D. Siqueira, Absolute Scale Reciprocal Space Mapping on X-ray Difractometers Incorporating a Position Sensitive Detector: Application to III-Nitride Semiconductors. Materials Science Forum, 2004. 455: pp.132-136.

DOI: 10.4028/www.scientific.net/msf.455-456.132

Google Scholar

[19] Li, L. and R.A. Overfelt, Influence of directional solidification variables on the cellular and primary dendrite arm spacings of PWA1484. Journal of Materials Science, 2002. 37: pp.3521-3532.

Google Scholar