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International Journal of Corrosion
Volume 2013 (2013), Article ID 824659, 11 pages
http://dx.doi.org/10.1155/2013/824659
Research Article

Combating Corrosion Degradation of Turbine Materials Using HVOF Sprayed 25% (Cr3C2-25(Ni20Cr)) + NiCrAlY Coating

1Metallurgical & Materials Engineering Department, National Institute of Technology Karnataka, Surathkal 575025, India
2Mechanical Engineering Department, National Institute of Technology Karnataka, Surathkal 575025, India

Received 16 July 2013; Revised 27 September 2013; Accepted 29 September 2013

Academic Editor: Ramazan Solmaz

Copyright © 2013 N. Jegadeeswaran et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

High velocity oxy fuel process (HVOF) is an advanced coating process for thermal spraying of coatings on to components used in turbines. HVOF process is a thermal spray coating method and is widely used to apply wear, erosion, and corrosion protective coatings to the components used in industrial turbines. 25% (Cr3C2-25(Ni20Cr)) + NiCrAlY based coatings have been sprayed on to three turbine materials, namely, Ti-31, Superco-605, and MDN-121. Coated and uncoated substrates were subjected to hot corrosion study under cyclic conditions. Each cycle consisted of 1 hour heating at 800°C followed by 20 minutes air cooling. Gravimetric measurements were done after each cycle and a plot of weight gain as a function of number of cycles is drawn. Parabolic rate constants were estimated for the understanding of corrosion behaviour. It was observed that coated Ti-31 and MDN-121 were more resistant compared to the uncoated ones. Uncoated superco-605 was undergoing sputtering during corrosion study and hence comparison between coated and uncoated superco-605 was difficult. The cross-sectional analysis of the corroded, coated samples indicated the presence of a thin layer of chromium oxide scale on the top of the coating and it imparted better corrosion resistance. Parabolic rate constants also indicated that coating is more beneficial to Ti-31 than to MDN-121.