The Effect of Initial Oxidation on Long-Term Oxidation of NiCoCrAlY Alloy

Chao Zhu, Xiaoyu Wu, Yuan Wu, Gongying Liang

.

DOI: 10.4236/eng.2010.28077                

Abstract

The initial oxidation behavior of Ni-6.5Co-17.8Cr-3.7Al-0.5Y alloy is investigated at 800°C-1000°C. X-ray diffraction results show that the dominant Cr2O3 phase and secondary α-Al2O3 and NiO phases are observed on the surface of samples at all initial stages (oxidized for 16 hours). YAlO3 and θ-Al2O3 can only be detected at low temperature (800°C) while the spinel NiCr2O4 is only observed at 900°C and 1000°C. Though the growth rates of α-Al2O3 and Cr2O3 are comparable at 900°C, the former becomes much lower than the latter when the temperature changes to 1000°C. Scanning electron microscopy (SEM) images show that the α-Al2O3 grows from some irregular ditches in the chromia scale at 900°C. However, cracking and spalling are more serious at 1000°C without α-Al2O3-grown-ditches, which is in accordance with the growth rates of these oxides at different temperatures. The cracking can be explained by the results of Raman determination which indicate that the stress on the surface of specimen oxidized at 1000°C is higher than that at 900°C. Owing to this condition, a preoxidation treatment on the NiCoCrAlY alloy for 16 hours is prepared at 900°C, and then thermal cycling oxidation test is conducted at 1000°C for 200 hours. The result indicates that the initial preoxidation treatment at 900°C improves the oxidation resistance of alloy at 1000°C.

Keywords

NiCoCrAlY, Oxidation Kinetics, Initial Oxidation, Al2O3, Cr2O3

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	N. P. Padture, M. Gell and E. H. Jordan, “Thermal Barrier Coatings for Gas-Turbine Engine Applications,” Science, Vol. 296, No. 5566, 2002, pp. 280-284.
[2]	A. G. Evans, D. R. Mumm, J. W. Hutchinson, G. H. Meier and F. S. Pettit, “Me-chanisms Controlling the Durability of Thermal Barrier Coat-ings,” Progress in Materials Science, Vol. 46, No. 5, 2001, pp. 505-553.
[3]	Y. Fengling and T. D. Bennett, “Phase of Ther-mal Emission Spectroscopy for Properties Measurements of Delaminating Thermal Barrier Coatings,” Journal of Applied Physics, Vol. 98, No. 10, 2005, pp. 103501- 103508.
[4]	R. Panat, S. L. Zhang and K. J. Hsia, “Bond Coat Surface Rum-pling in Thermal Barrier Coatings,” Acta Materialia, Vol. 51, No. 1, 2003, pp. 239-249.
[5]	B. Wang, J. Gong, A. Y. Wang, C. Sun, R. F. Huang and L. S. Wen, “Oxidation Behaviour of Nicraly Coatings on Ni-Based Superalloy,” Surface & Coatings Technology, Vol. 149, No. 1, 2002, pp. 70-75.
[6]	U. Schulz, C. Leyens, K. Fritscher, M. Peters, B. Saruhan-Brings, O. La-vigne, J. M. Dorvaux, M. Poulain, R. Mevrel and M. L. Caliez, “Some Recent Trends in Research and Technology of Advanced Thermal Barrier Coatings,” Aerospace Science and Technology, Vol. 7, No. 1, 2003, pp. 73-80..
[7]	R. A. Mahesh, R. Jayaganthan and S. Prakash, “Microstructural Characteristics and Mechanical Pro- perties of HVOF Sprayed Nicral Coating on Super- alloys,” Journal of Alloys and Compounds, Vol. 468, No. 1-2, 2009, pp. 392-405.
[8]	T. F. An, H. R. Guan, X. F. Sun and Z. Q. Hu “Effect of the Theta-Alpha-Al2O3 Transformation in Scales on the Oxidation Behavior of a Nickel-Base Superalloy with an Aluminide Diffusion Coating,” Oxidation of Metals, Vol. 54, No. 3-4, 2000, pp. 301-316.
[9]	S. O. Moussa and K. Morsi, “High-Temperature Oxidation of Reactively Processed Nickel Aluminide Intermetallics,” Journal of Alloys and Compounds, Vol. 426, No. 1-2, 2006, pp. 136-143.
[10]	T. J. Nijdam, N. M. van der Pers and W. G. Sloof, “Oxide Phase Development upon High Temperature Oxidation of Gamma-Nicral Alloys,” Materials and Corrosion- Werkstoffe Und Korrosion, Vol. 57, No. 3, 2006, pp. 269- 275.
[11]	M. Kemdehoundja, J. F. Dinhut, J. L. Grosseau-Poussard and M. Jeannin, “High Temperature Oxida-tion of Ni70Cr30 Alloy: Determination of Oxidation Kinetics and Stress Evolution in Chromia Layers,” Materials Science and Engineering A, Vol. 435-436, No. 5, 2006, pp. 666-671.
[12]	G. Calvarin, A. M. Huntz, A. Hugot Le Goff, S. Joiret and M. C. Bernard, “Oxide Scale Stress Determination by Raman Spec-troscopy Application to the Nicr/Cr2O3 System and Influence of Yttrium,” Scripta Materialia, Vol. 38, No. 11, 1998, pp. 1649-1658.
[13]	P. Kofstadt, “High Temperature Corrosion,” Elsevier, New York, 1988.
[14]	D. Lee, M. L. Santella, I. M. Anderson and G. M. Pharr “Thermal Aging Effects on the Mi-crostructure and Short- Term Oxidation Behavior of a Cast Ni3Al Alloy,” Intermetallics, Vol. 13, No. 2, 2005, pp. 187-196.
[15]	S. Seal, S. C. Kuiry and L. A. Bracho, “Surface Chemistry of Oxide Scale on IN-738LC Superalloy: Effect of Long-Term Exposure in Air at 1173 K,” Oxidation of Metals, Vol. 57, No. 3-4, 2002, pp. 297-322.
[16]	S. C. Choi, H. J. Cho and D. B. Lee, “Effect of Cr, Co, and Ti Additions on the High-Temperature Oxidation Behavior of Ni3Al,” Oxidation of Metals, Vol. 46, No. 1-2, 1996, pp. 109-127.
[17]	H. H. An-germann, K. Nishi, Y. Aono, M. Inagaki and H. Kodama, “Evolution of Oxides on Ni-Base ODS Superalloys,” Oxidation of Metals, Vol. 48, No. 1-2, 1997, pp. 1-39.