Effect of Mo on the High Temperature Oxidation Behavior of Co-Al-W Based Alloys

Abstract:

2 at.% and 4 at.% Mo were added to Co-9Al-9W-2Ta-0.02B alloy to replace W (hereafter referred to as the alloys of 2Mo and 4Mo, respectively; Mo-free alloy was referred to as the 0Mo alloy). The effects of Mo additions on the high temperature oxidation behavior of the alloys at 800 °C in air have been studied. The results indicated that, after oxidation in air at 800 °C for 100 h, the oxide film of the 0Mo alloy remained intact, but the cracking and spallation of the oxide film took place in the alloys of 2Mo and 4Mo. Oxidation kinetic curves revealed weight gain per unit area of the 0Mo alloy was 36.86 mg·cm^-2, which was lower than that of the alloys of 2Mo (65.16 mg·cm^-2) and 4Mo (48.54mg·cm^-2). These suggested that the 0Mo alloy displayed superior oxidation resistance compared to the alloys of 2Mo and 4Mo caused by the formation of volatile MoO₃ oxide, and sharp compressive stress formed in the outer layer during the oxidation. The oxide layer was composed of three layers of the Co₃O₄ + CoO outer layer, middle complex oxide layer containing Co, Al and W (Mo), inner Al₂O₃ layer and γ/Co₃W zone adhere to the γ/γ' substrate.

• Periodical: Materials Science Forum (Volumes 747-748)
• Pages: 754-759
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.747-748.754
• Online since: February 2013
• Authors: Fei Fan, Hao Sun, Di Zhao, Jiang Bo Sha
• Keywords: Co-Based Superalloy, High-Temperature Oxidation, Molybdenum, Oxide Layer

References

[1] Beltran AM. In: Superalloys II. New York (NY): Wiley; 1987 p.135.

[2] Akane Suzukia, Tresa M. Pollock, High-temperature strength and deformation of γ/γ' two-phase Co–Al–W-base alloys, J. Acta Materialia, 2008 56(6) 1288–1297.

DOI: 10.1016/j.actamat.2007.11.014

[3] J. Sato, T. Omori, K. Oikawa, et al. Cobalt-base high-temperature alloys, J. Science, 2006 312(5770) 90-91.

DOI: 10.1126/science.1121738

[4] T.M. Pollock, J. Dibbern, M. Tsunekane, J. Zhu, A. Suzuki, New Co-based γ/γ' high temperature alloys, J. JOM Journal of the Minerals, Metals and Materials Society, 2010 62(1) 58-63.

DOI: 10.1007/s11837-010-0013-y

[5] L. Klein, A. Bauer, S. Neumeier, et al. High temperature oxidation of γ/γ'-strengthened Co-base superalloys, J. Corrosion Science, 2011 53(5) 2027–(2034).

DOI: 10.1016/j.corsci.2011.02.033

[6] L. Klein, Y. Shen, M.S. Killian, et al. Effect of B and Cr on the high temperature oxidation behavior of novel γ/γ'-strengthened Co-base superalloys, J. Corrosion Science, 2011 53(9) 2713–2720.

DOI: 10.1016/j.corsci.2011.04.020

[7] XU Yangtao, XIA Tiandong, YAN Jian-qiang, Effect of alloying elements on oxidation behavior of Co-Al-W alloys at high temperature, J. The Chinese Journal of Nonferrous Metals, 2010 20(11) 2168-2177.

[8] LI Hao, SHA Jiangbo, LI Shusuo. Microstructures and mechanical properties of alloys Co-9Al-(9-x)W-xMo-2Ta-0. 02B at Room and High Temperatures, J. Acta Aeronautica et Astronautica Sinica, 2011 32(6) 1139-1146.

[9] Steffen Burk, Bronislava Gorr, Daniel Schliephake, et al. High-temperature oxidation behavior of a single-phase (Mo, Ti)5Si3 (Mo–Si–Ti) alloy, J. Scripta Materialia, 2011 66(2012) 223–226.

DOI: 10.1016/j.scriptamat.2011.10.042

[10] Satoru Kobayashi, Yuki Tsukamoto, Takayuki Takasugi, et al. Determination of phase equilibria in the Co-rich Co–Al–W ternary system with a diffusion-couple technique, J. Intermetallics, 2009 17(12) 1085–1089.

DOI: 10.1016/j.intermet.2009.05.009

[11] Sharma Paswan, R. Mitra and S.K. Roy. Nonisothermal and cyclic oxidation behavior of Mo-Si-B and Mo-Si-B-Al alloys, J. Metallurgical and Materials Transactions A, 2009 40(11) 2644-2658.

DOI: 10.1007/s11661-009-9946-6

[12] K. Chattopadhyay, R. Mitra, K.K. Ray. Nonisothermal and isothermal oxidation behavior of Nb-Si-Mo Alloys, J. Metallurgical and Materials Transactions A, 2008 39(3) 577-592.

DOI: 10.1007/s11661-007-9398-9