The corrosion behavior of the Ni3Al/Ni3V two-phase intermetallic compounds with and without minor elements (Nb, Co, and Cr) to be composed of L12 phase (Ni3Al) and a mixed phase of L12 (Ni3Al) and D022 (Ni3V) has been investigated by using an immersion test in 0.5？kmol/m3 HCl, H2SO4, and HNO3 solutions. The surface morphology was observed before and after the immersion test by scanning electron microscope (SEM). The results were compared to those of the L12 single-phase Ni3(Si,Ti) and austenitic stainless steel type 304. In all acidic solutions, preferential dissolution of ( ) phase was found in Ni3Al/Ni3V, but no intergranular attack, whereas the attacks took place on Ni3(Si,Ti). The Ni3Al/Ni3V showed a higher corrosion resistance in HCl solution and a lower resistance in HNO3 solution than Ni3(Si,Ti) and type 304. The addition of the minor elements enhanced corrosion resistance in HNO3 solution, but not clearly in HCl and H2SO4 solutions. In HCl and H2SO4, their weight losses during the immersion test were almost the same. 1. Introduction Recently, Ni-Al-V intermetallic compounds with a two-phase microstructure of Ni3Al (L12) and Ni3V (D022) phases have been developed by Takasugi et al. [1–13] and are confirmed to exhibit a highly coherent interface between these constituent phases. They have superior mechanical properties (i.e., high creep rapture life, high hardness, low thermal expansion, and better thermal conductivity) and also have high tensile strength and fracture toughness over a broad range of temperature in comparison with those of Inconel 750, Inconel 718 and Hastelloy [1–13]. Therefore, the Ni3Al/Ni3V two-phase intermetallic compounds are a candidates as materials in land-based, marine-based, and aero-gas turbine industries (turbine blade), high strength nut and bolt, and high temperature bearing or high temperature tool [8, 9, 14]. However, many studies revealed that the intermetallic compounds containing aluminum are very susceptible to hydrogen embrittlement [15–18], where hydrogen embrittlement takes place with permeation of atomic hydrogen formed by corrosion reaction into the compounds. Hence, to suppress this environmental embrittlement a small amount of boron was added to these compounds. However, it was reported that the boron segregation at grain boundaries became the preferential dissolution site and led to the intergranular attack in the L12 single-phase Ni3(Si,Ti) [19]. Furthermore, Ni base intermetallic compounds such as single-phase Ni3(Si,Ti) have attractive properties for high-temperature structural material (e.g., high
References
[1]
Y. Nunomura, Y. Kaneno, H. Tsuda, and T. Takasugi, “Phase relation and microstructure in multi-phase intermetallic alloys based on Ni3Al-Ni3Ti-Ni3V pseudo-ternary alloy system,” Intermetallics, vol. 12, no. 4, pp. 389–399, 2004.
[2]
Y. Nunomura, Y. Kaneno, H. Tsuda, and T. Takasugi, “Dual multi-phase intermetallic alloys composed of geometrically close-packed Ni3X (X: Al, Ti and V) type structures—I. Microstructures and their stability,” Acta Materialia, vol. 54, no. 3, pp. 851–860, 2006.
[3]
W. Soga, Y. Kaneno, and T. Takasugi, “Phase relation and microstructure in multi-phase intermetallic alloys based on Ni3Al-Ni3Nb-Ni3V pseudo-ternary alloy system,” Intermetallics, vol. 14, no. 2, pp. 170–179, 2006.
[4]
S. Shibuya, Y. Kaneno, M. Yoshida, T. Shishido, and T. Takasugi, “Mechanical properties of dual multi-phase single-crystal intermetallic alloy composed of geometrically close packed Ni3X (X: Al and V) type structures,” Intermetallics, vol. 15, no. 2, pp. 119–127, 2007.
[5]
S. Shibuya, Y. Kaneno, H. Tsuda, and T. Takasugi, “Microstructural evolution of dual multi-phase intermetallic alloys composed of geometrically close packed Ni3X (X: Al and V) type structures,” Intermetallics, vol. 15, no. 3, pp. 338–348, 2007.
[6]
Y. Kaneno, W. Soga, H. Tsuda, and T. Takasugi, “Microstructural evolution and mechanical property in dual two-phase intermetallic alloys composed of geometrically close-packed Ni3X (X: Al and V) containing Nb,” Journal of Materials Science, vol. 43, no. 2, pp. 748–758, 2008.
[7]
W. Soga, Y. Kaneno, M. Yoshida, and T. Takasugi, “Microstructure and mechanical property in dual two-phase intermetallic alloys composed of geometrically close-packed Ni3X (X: Al and V) containing Nb,” Materials Science and Engineering A, vol. 473, no. 1-2, pp. 180–188, 2008.
[8]
T. Takasugi and Y. Kaneno, “Plasma-assisted surface modification of two-phase intermetallic alloy composed of Ni3X type structures,” in Proceedings of the MRS Symposium, vol. 1128, U06-04, 2009.
[9]
Y. Kaneno, N. Matsumoto, N. Tsuji, S. Tanaka, and T. Takasugi, “Plasma-assisted surface hardening of dual two-phase intermetallic alloy composed of Ni3X type structures,” Materials Science and Engineering A, vol. 516, no. 1-2, pp. 84–89, 2009.
[10]
K. Kawahara, Y. Kaneno, A. Kakitsuji, and T. Takasugi, “Microstructural factors affecting hardness property of dual two-phase intermetallic alloys based on Ni3Al-Ni3V pseudo-binary alloy system,” Intermetallics, vol. 17, no. 11, pp. 938–944, 2009.
[11]
Y. Kitaura, Y. Kaneno, and T. Takasugi, “Effect of TiC addition on mechanical properties of dual two-phase Ni3Al-Ni3V intermetallic alloy,” Intermetallics, vol. 18, no. 8, pp. 1623–1631, 2010.
[12]
Y. Kitaura, Y. Kaneno, and T. Takasugi, “Effect of NbC addition on mechanical properties of dual two-phase Ni3Al-Ni3V intermetallic alloy,” Materials Science and Engineering A, vol. 527, no. 21-22, pp. 6012–6019, 2010.
[13]
K. Kawahara, T. Moronaga, Y. Kaneno, A. Kakitsuji, and T. Takasugi, “Effect of Nb and Ti addition on microstructure and hardness of dual two-phase intermetallic alloys based on Ni3Al-Ni3V pseudo-binary alloy system,” Materials Transactions, vol. 51, no. 8, pp. 1395–1403, 2010.
[14]
R. Schafric and R. Sprague, Advanced Materials Process, vol. 162, pp. 27–30, 2004.
[15]
L. Y. Fang, G. J. Ting, and S. Y. Fu, The Transactions of Nonferrous Metals Society of China, vol. 16, pp. 368–375, 2007.
[16]
C. T. Liu, E. H. Lee, and C. G. Mckamey, “An environmental effect as the major cause for room-temperature embrittlement in FeAI,” Scripta Metallurgica et Materialia, vol. 23, pp. 875–880, 1989.
[17]
C. T. Liu and E. P. George, “Environmental embrittlement in boron-free and boron-doped feal (40 at. % AI) alloys,” Scripta Metallurgica Materialia, vol. 24, pp. 1285–1290, 1990.
[18]
D. J. Duquette, Intermetallic Compounds, vol. 1, John Willey & Sons, 1994.
[19]
G. Priyotomo, K. Okitsu, A. Iwase, Y. Kaneno, R. Nishimura, and T. Takasugi, “The corrosion behavior of intermetallic compounds Ni3(Si,Ti) and Ni3(Si,Ti) + 2Mo in acidic solutions,” Applied Surface Science, vol. 257, no. 19, pp. 8268–8274, 2011.
[20]
D. Schlain, C. B. Kenahan, and W. L. Acherman, “Corrosion properties of high-purity vanadium,” Journal of The Less-Common Metals, vol. 3, no. 6, pp. 458–467, 1961.
[21]
T. Moronaga, Y. Kaneno, H. Tsuda, and T. Takasugi, “TEM observation of the channel regions in a two-phase intermetallic alloy based on Ni3Al-Ni3V pseudo-binary alloy system,” Intermetallics, vol. 21, pp. 80–87, 2012.
