鎳基合金銲件銲道之沿晶腐蝕及枝晶間腐蝕(Interdendritc corrosion, IDC)為化學工廠、核電廠銲接管路常見的劣化現象。本研究針對鎳基合金Alloy 82覆銲層(Cladding)之衰化缺陷，探討以雷射表面處理(Laser surface treatment, LST)進行修復之可能性。實驗首先以敏化熱處理模擬不當銲接引起衰化或長時間使用後之低溫敏化，使試件發生枝晶間局部析出造成耐蝕能力下降，再透過不同能量密度之LST進行修復工作。觀察LST前後顯微組織變化，並使用惠氏試驗法及雙環動電位再活化測試法評估其耐蝕能力改善範圍/程度。
實驗結果顯示，衰化覆銲層在腐蝕測試中發生枝晶間局部腐蝕，而經雷射處理之重熔區及熱影響區則未發生腐蝕。原因為雷射掃描過程中，鉻、鈮析出物重新熔回鎳基地，消除枝晶間局部缺鉻區而恢復耐蝕性能。熱影響區雖未發生熔融，但由微觀組織上即可見其晶間富鈮相在高溫熱歷程中，亦固溶回枝晶內部而恢復耐蝕能力。而電化學腐蝕測試中，雷射處理試件之重熔、熱影響區皆可測得較低的再活化電流，其敏化值(Ir/Ia)低於衰化試件，因此確認雷射表面處理為有效之修補方式。

The Intergranular corrosion (IGC) and Interdendritic corrosion (IDC) cracking were detected in nickel based alloy weldment of chemical factories and nuclear power plants. Laser surface treatment is studied here as a feasible method to repair the decayed Alloy 82 weldment where weld decayed zone is rejuvenated and corrosion resistance is recovered. Influence of laser processing parameters on the microstructural modification is focused. A modified Huey test was used to reveal the width of rejuvenated area, and double loop-EPR test was employed to evaluate the corrosion resistance of each specimen.
The experimental results showed that interdendritic pitting resistance of laser treated specimens is remarkably improved both in melted zone and heat affected zone where Nb-rich phases are resolved. The DL-EPR results revealed that laser treated specimens with lower reactivation current and degree of sensitization values (DOS, Ir/Ia) indicate higher corrosion resistance. Laser surface treatment is proven to be a practical technique for repairing the decayed Alloy 82 weldment.

1. S.R.D. S.E. Cumblidge, G.J. Schuster, R.V. Harris, S.L. Crawford, R.J. Seffens, M.B. Toloczko, NDE and DE of PWSCC Found in the J-Groove Weld of a Removed-From-Service Control Rod Drive Mechanism, in 6th International Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurized Components. 2007, Budapest, Hungary.
2. S.F. Hongqing Xu, James W. Hyres. "Laboratory Investigation of the Stainless Steel Cladding on the Davis-Besse Reactor Vessel Head," in Proceedings of the 12th International Conference on Environmental Degradation of Materials in Nuclear Power System, 2005.
3. H.L. Rick Rishel, Greg Turley,Bruce Newton. "Recent Field Experience and Lessons Learned," in International conference Nuclear Energy for New Europe 2007, Ljubljana, Slovenia, 2007.
4. J.H. Chang, T.H. Liu, J.M. Chou, R.I. Hsieh, and J.L. Lee, "Microstructural and microhardness characteristics of induction melted nickel-based alloys," Materials Chemistry and Physics, Vol.120 (2-3), 2010, pp. 702-708.
5. H.P. Seifert, S. Ritter, T. Shoji, Q.J. Peng, Y. Takeda, and Z.P. Lu, "Environmentally-assisted cracking behaviour in the transition region of an Alloy182/SA 508 Cl.2 dissimilar metal weld joint in simulated boiling water reactor normal water chemistry environment," Journal of Nuclear Materials, Vol.378 (2), 2008, pp. 197-210.
6. C. Jang, J. Lee, J.S. Kim, and T.E. Jin, "Mechanical property variation within Inconel 82/182 dissimilar metal weld between low alloy steel and 316 stainless steel," International Journal of Pressure Vessels and Piping, Vol.85 (9), 2008, pp. 635-646.
7. Q. Peng, T. Shoji, H. Yamauchi, and Y. Takeda, "Intergranular environmentally assisted cracking of Alloy 182 weld metal in simulated normal water chemistry of boiling water reactor," Corrosion Science, Vol.49 (6), 2007, pp. 2767-2780.
8. R. Rios, T. Magnin, D. Noel, and O. Debouvier, "Critical Analysis of Alloy-600 Stress-Corrosion Cracking Mechanisms in Primary Water," Metallurgical and Materials Transactions A-Physical Metallurgy and Materials Science, Vol.26 (4), 1995, pp. 925-939.
9. T. Magnin, D. Noel, and R. Rios, "Microfractographic Aspects of Stress-Corrosion Cracking of Inconel 600 in a Pressurized-Water Reactor Environment," Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing, Vol.177 (1-2), 1994, pp. L11-L14.
10. G. Bao, K. Shinozaki, S. Iguro, M. Inkyo, M. Yamamoto, Y. Mahara, and H. Watanabe, "Stress corrosion cracking sealing in overlaying of Inconel 182 by laser surface melting," Journal of Materials Processing Technology, Vol.173 (3), 2006, pp. 330-336.
11. 鄭勝隆, 鎳基690合金與SUS304不銹鋼異種金屬銲接特性與微結構研究, in 國立成功大學博士論文. 2003, 國立成功大學, 台南.
12. 游季陸, 鎳基182合金銲道敏化現象之研究, in 國立成功大學碩士論文. 2003, 國立成功大學, 台南.
13. 郭聰源, 鎳基690合金銲件之特性與組織改善研究, in 國立成功大學博士論文. 1999, 國立成功大學, 台南.
14. 葉東昌, 鎳基690銲件之特性與組織改善研究, in 國立成功大學碩士論文. 1997, 國立成功大學, 台南.
15. T.R. AnthonyandH.E. Cline, "Surface Normalization of Sensitized Stainless-Steel by Laser Surface Melting," Journal of Applied Physics, Vol.49 (3), 1978, pp. 1248-1255.
16. Y.S. Lim, H.P. Kim, J.H. Han, J.S. Kim, and H.S. Kwon, "Influence of laser surface melting on the susceptibility to intergranular corrosion of sensitized Alloy 600," Corrosion Science, Vol.43 (7), 2001, pp. 1321-1335.
17. J.H. Suh, J.K. Shin, S.J.L. Kang, Y.S. Lim, I.H. Kuk, and J.S. Kim, "Investigation of IGSCC behavior of sensitized and laser-surface-melted Alloy 600," Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing, Vol.254 (1-2), 1998, pp. 67-75.
18. J.K. Shin, J.H. Suh, J.S. Kim, and S.J.L. Kang, "Effect of laser surface modification on the corrosion resistance of Alloy 600," Surface & Coatings Technology, Vol.107 (2-3), 1998, pp. 94-100.
19. G. Bao, M. Yamamoto, and K. Shinozaki, "Precipitation and Cr depletion profiles of Inconel 182 during heat treatments and laser surface melting," Journal of Materials Processing Technology, Vol.209 (1), 2009, pp. 416-425.
20. Y.S. Lim, H.P. Kim, H.D. Cho, and H.H. Lee, "Microscopic examination of an Alloy 600/182 weld," Materials Characterization, Vol.60 (12), 2009, pp. 1496-1506.
21. A.J. Craven, K. He, L.A.J. Garvie, and T.N. Baker, "Complex heterogeneous precipitation in titanium-niobium microalloyed Al-killed HSLA steels - II. Non-titanium based particles," Acta Materialia, Vol.48 (15), 2000, pp. 3869-3878.
22. A.J. Craven, K. He, L.A.J. Garvie, and T.N. Baker, "Complex heterogeneous precipitation in titanium-niobium microalloyed Al-killed HSLA steels - I. (Ti,Nb)(C,N) particles," Acta Materialia, Vol.48 (15), 2000, pp. 3857-3868.
23. M. Leonhardt, W. Loser, and H.G. Lindenkreuz, "Solidification kinetics and phase formation of undercooled eutectic Ni-Nb melts," Acta Materialia, Vol.47 (10), 1999, pp. 2961-2968.
24. L.A. RaufandJ.D. Boyd, "Microstructural evolution during thermomechanical processing of a Ti-Nb interstitial-free steel just below the Ar-3 temperature," Metallurgical and Materials Transactions a-Physical Metallurgy and Materials Science, Vol.28 (7), 1997, pp. 1437-1443.
25. H.M. Tawancy, I.M. Allam, and N.M. Abbas, "Effect of Ni3nb Precipitation on the Corrosion-Resistance of Inconel Alloy 625," Journal of Materials Science Letters, Vol.9 (3), 1990, pp. 343-347.
26. M. Momeni, M.H. Moayed, and A. Davoodi, "Tuning DOS measuring parameters based on double-loop EPR in H2SO4 containing KSCN by Taguchi method," Corrosion Science, Vol.52 (8), 2010, pp. 2653-2660.
27. V. KainandY. Watanabe, "Development of a single loop EPR test method and its relation to grain boundary microchemistry for alloy 600," Journal of Nuclear Materials, Vol.302 (1), 2002, pp. 49-59.
28. T.F. Wu, T.P. Cheng, and W.T. Tsai, "The electrochemical potentiokinetic reactivation behavior of Alloy 600," Materials Chemistry and Physics, Vol.70 (2), 2001, pp. 208-216.
29. T.F. Wu, T.P. Cheng, and W.T. Tsai, "Effect of electrolyte composition on the electrochemical potentiokinetic reactivation behavior of Alloy 600," Journal of Nuclear Materials, Vol.295 (2-3), 2001, pp. 233-243.
30. M.K. Ahn, H.S. Kwon, and J.H. Lee, "Predicting Susceptibility of Alloy-600 to Intergranular Stress-Corrosion Cracking Using a Modified Electrochemical Potentiokinetic Reactivation Test," Corrosion, Vol.51 (6), 1995, pp. 441-449.
31. S. Yang, Z.J. Wang, H. Kokawa, and Y.S. Sato, "Reassessment of the effects of laser surface melting on IGC of SUS 304," Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing, Vol.474 (1-2), 2008, pp. 112-119.
32. R. Blondeau, "Metallurgy and Mechanics of Welding," 2008, Wiley.
33. H. Okamoto, "Nb-Ni (niobium-nickel)," Journal of Phase Equilibria and Diffusion, Vol.29 (2), 2008, pp. 210-210.
34. H. Okamoto, "Nb-Ni (Niobium-Nickel)," Journal of Phase Equilibria and Diffusion, Vol.27 (3), 2006, pp. 314-314.
35. H. Okamoto, "Nb-Ni (niobium-nickel)," Journal of Phase Equilibria, Vol.19 (3), 1998, pp. 289-289.
36. G.K. Allan, "Solidification of austenitic stainless steels," Ironmaking & Steelmaking, Vol.22 (6), 1995, pp. 465-477.
37. K. Rajasekhar, C.S. Harendranath, R. Raman, and S.D. Kulkarni, "Microstructural evolution during solidification of austenitic stainless steel weld metals: A color metallographic and electron microprobe analysis study," Materials Characterization, Vol.38 (2), 1997, pp. 53-65.
38. D.J.K. John C. Lippold, "Welding Metallurgy and Weldability of Stainless Steel," 2005, Wiley-Interscience.
39. 曾秉鈞, 雷射表面重熔參數對SUS304敏化不銹鋼去敏化之影響, in 國立成功大學碩士論文. 2009, 國立成功大學, 台南.
40. W.M. Steen, "Laser Material Processing," 1991, London, Springer-Verlag.
41. A.B. M. von Allmen, "Laser-Beam Interactions with Materials." Physical Principles and Applications, ed. M.B.P. U.Gonser, M.Osgood, H. Sakaki, 1995, Heidelberg, Springer.
42. J.E.I. S. Liu "Metal Handbook." Irons, Steels and High-Performance Alloy, Vol. 1, 1989.
43. K. Stiller, J.O. Nilsson, and K. Norring, "Structure, chemistry, and stress corrosion cracking of grain boundaries in alloys 600 and 690," Metallurgical and Materials Transactions a-Physical Metallurgy and Materials Science, Vol.27 (2), 1996, pp. 327-341.
44. M. ThuvanderandK. Stiller, "Evolution of grain boundary chemistry in a Ni-17Cr-9Fe model alloy," Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing, Vol.250 (1), 1998, pp. 93-98.
45. ASTM, Standard Test Method for Electrochemical Reactivation (EPR) for Detecting Sensitization of AISI Type 304 and 304L Stainless Steels. 2010.
46. ASTM, Standard Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels 2002.
47. ASTM, Standard Practice for Preparation and Use of Bent-Beam Stress-Corrosion Test Specimens. 2011.
48. J.N. DuPont, C.V. Robino, J.R. Michael, M.R. Notis, and A.R. Marder, "Solidification of Nb-bearing superalloys: Part I. Reaction sequences," Metallurgical and Materials Transactions a-Physical Metallurgy and Materials Science, Vol.29 (11), 1998, pp. 2785-2796.
49. J.N. DuPont, C.V. Robino, A.R. Marder, and M.R. Notis, "Solidification of Nb-bearing superalloys: Part II. Pseudoternary solidification surfaces," Metallurgical and Materials Transactions a-Physical Metallurgy and Materials Science, Vol.29 (11), 1998, pp. 2797-2806.
50. J.N. Dupont, C.V. Robino, and A.R. Marder, "Modeling solute redistribution and microstructural development in fusion welds of Nb-bearing superalloys," Acta Materialia, Vol.46 (13), 1998, pp. 4781-4790.
51. J.N. Dupont, C.V. Robino, and A.R. Marder, "Solidification and weldability of Nb-bearing superalloys," Welding Journal, Vol.77 (10), 1998, pp. 417s-431s.
52. 洪聖凱, 不銹鋼銲件沿晶應力腐蝕劣化之雷射表面重熔修補技術研究, in 國立成功大學碩士論文. 2010, 國立成功大學, 台南.