Abstract
The failure of the circulation pump in a sulfur recovery unit occurred after 11 years of operation, during which it was exposed to the weak acid process stream. The A494-CW6M impeller of the pump was found to be completely shattered, leading to the failure. Despite the long operating period, the failure appearance was unusual, and further investigation was needed to understand the cause of the failure. To this end, the detailed metallurgical characterization was performed using the electron microscope and commercially available thermodynamic software. The experimental results showed that the leached regions exhibited more than 50% of the impeller thickness, and those were matched with topological closed phases (M6C, Sigma, P phase), which commonly had low Cr (10 ~ 11 wt.%) and high Mo (56 ~ 58 wt.%) composition. The failure was attributed to the weak corrosion resistance of the low Cr phases when exposed to oxidizing weak acid streams. In addition, thermodynamic phase calculation showed that a large amount of TCPs precipitation was likely due to the malpractice of the heat treatment process. The detailed failure analysis result will be discussed in the present paper.
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G.A. Cragnolino, D.S. Dunn, C.S. Brossia, V. Jain, and K.S. Chan, Assessment of performance issues related to alternate engineered barriers system materials and design options, nuclear regulatory commission, contract NRC-02-97-009 (1999)
G.E. Gdowski, Survey of degradation modes of four nickel-chromium-molybdenum alloys (1991)
F.G. Hodge, Effect of aging on the anodic behavior of Ni-Cr-Mo alloys. Corrosion. 29(10), 375–383 (1973)
M.A. Streicher, Relationship of heat treatment and microstructure to corrosion resistance in wrought Ni-Cr-Mo alloys. Corrosion. 19(8), 272t–284t (1963)
R.B. Leonard, Thermal stability of hastelloy alloys C-276. Corrosion. 25(5), 222–228 (1969)
C.H. Samans, A.R. Meyer, G.F. Tisinai, Sensitization and thermal stabilization of Ni-Cr-Mo-Fe-W alloy. Corrosion. 22(12), 336–345 (1966)
R.B. Leonard, The electrochemical behavior of some nickel base and cobalt base alloys. Corrosion. 24(9), 301–307 (1968)
C.E. Bates, L.C. Tilery, Atlas of Cast Corrosion Resistant Alloy Microstructure, 1st ed., Steel Founders' Society of America, p 99~123 (1985)
N.S. Zadorozne, M.A. Rodríguez, R.M. Carranza, S.M. Meck, and R.B. Rebak, Corrosion resistance of Ni-Cr-Mo and Ni-Mo-Cr alloys in different metallurgical conditions, corrosion 2010, March (San Antonio, Texas, USA), NACE International, Paper No. 10236 (2010)
U.L. Heubner, E. Altpeter, M.B. Rockel, E. Wallis, Electrochemical and its composition and sensitization of NiCrMo alloys in ASTM G-28 solution. Corrosion. 45(3), 249–259 (1989)
L.A. Giannuzzi, F.A. Stevie, A review of focused ion beam milling techniques for TEM specimen preparation. Micron. 30(3), 197 (1999)
M. Raghavan, B.J. Berkowitz, J.C. Scanlon, Electron microscopic analysis of heterogeneous precipitates in hastelloy C-276. Metall. Trans. A. 13A, 979–984 (1982)
H.M. Twancy, On the precipitation of intermetallic compounds in selected solid-solution-strengthened Ni-base alloys and their effects on mechanical properties. Metallogr. Microstruct. Anal. 6, 200–215 (2017)
H.S. Betrabet, K. Nishimoto, B.E. Wilde, W.A.T. Clark, Electrochemical and microstructural investigation of grain boundary precipitation in AISI 304 stainless steels containing nitrogen. Corrosion. 43(2), 77–84 (1987)
W.-S. Choi, H. Park, Comments on “formation of M23C6-type precipitates and chromium-depleted zones in austenite stainless steel.” Scr. Mater. 65, 509–512 (2011)
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Ro, Y., Choi, WS., Park, H. et al. Failure Analysis of Casting Ni-Cr-Mo Impeller After Long-Term Weak Acid Exposure. J Fail. Anal. and Preven. 24, 510–519 (2024). https://doi.org/10.1007/s11668-023-01852-z
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DOI: https://doi.org/10.1007/s11668-023-01852-z