本研究以低碳鋼熱浸鍍鋁鉻、熱浸鍍鋁鉻矽，探討鍍浴中添加不同含量之鉻與矽對於鍍層之顯微結構與相變化，並以高溫恆溫氧化與循環氧化探討鍍層之抗氧化性。
熱浸溫度750 ℃ 與 850 ℃，熱浸鍍鋁鉻之鍍層組成結構，由試片表面至低碳鋼底材依序為純鋁層、Al7Cr、FeAl3與Fe2Al5。熱浸鍍鋁鉻與傳統熱浸鍍鋁相比，鍍層總厚度較厚。然而氧化增重結果顯示熱浸鍍鋁鉻之抗氧化性不佳。熱浸鍍鋁鉻試片經高溫氧化後試片表面雖生成緻密氧化鋁，氧化皮膜與FeAl層之結合力較差，因此產生剝落。過厚之鐵鋁相導致鍍層容易因熱應力產生破裂，使得在試片表面也觀察到許多裂縫。熱浸鍍鋁鉻矽之鍍層組成相，由試片表面至低碳鋼底材依序為純鋁層、Al7(FeCr)Si與Fe2Al5。熱浸鍍鋁鉻矽之試片合金化層較薄產生之熱應力較小，因此熱浸鍍鋁鉻矽氧化增重之表現較優於熱浸鍍鋁鉻。熱浸鍍鋁鉻矽試片經高溫氧化後，試片表面同樣生成緻密之氧化鋁，但也有因熱應力所形成之裂縫。

This study investigated the microstructural and phase changes of the coating by adding different levels of chromium and silicon in the bath.
The composition of the hot-dip chromium aluminium coating from the surface of the samples to the low carbon steel substrate was in the order of pure aluminium, Al7Cr, FeAl3 and Fe2Al5. Hot dip Al-Cr total thickness of the coating was thicker than that of conventional hot-dip aluminium coating. However, the oxidation weight gain results show that the oxidation resistance of hot dip Al-Cr is not good. Although dense aluminium oxide is formed on the surface of the specimens after high temperature oxidation, the oxide film does not bond well with the FeAl layer and therefore flaking occurs. The thicker FeAl phase causes the coating to break easily due to heat stress, resulting in many cracks being observed on the surface of the specimen. The composition of the hot dip Al-5Cr-1Si layer is pure aluminium, Al7(FeCr)Si and Fe2Al5 from the surface of the specimen to the low carbon steel substrate, the thinner alloyed layer of the hot dip Al-5Cr-1S samples generates less heat stress and therefore the oxidation weight gain of the hot dip AlCrSi is better than that of the hot dip AlCrSi. When the samples are oxidised at high temperature, the surface of the samples also produces dense aluminium oxide, but there are also cracks caused by heat stress.

[1]Y. N. Chang and F. I. Wei, "High temperature oxidation of low alloy steels," Journal of materials science, vol. 24, no. 1, pp. 14-22, 1989.
[2]G. Xu, K.Wang , X.Dong and L.Yang ,"Review on corrosion resistance of mild steels in liquid aluminum," Journal of Materials Science & Technology, vol. 71, pp. 12-22, 2021.
[3]C. J. Wang and S. M. Chen, "The high-temperature oxidation behavior of hot-dipping Al-Si coating on low carbon steel,"Surface and coatings technology, vol. 200, no. 22-23, pp. 6601-6605, 2006.
[4]H. H. Liu,W. J. Cheg and C. J.Wang,"The mechanism of oxide whisker growth and hot corrosion of hot-dipped Al–Si coated 430 stainless steels in air–NaCl (g) atmosphere," Applied surface science, vol. 257, no. 24, pp. 10645-10652, 2011.
[5]Z. Wang, T. Liu , E. Wang, S. Hu, Z. Xie and X. Gong, "Effect of Al plating on growth behavior of TGO layer in CoCrNiAlY–YSZ–RSZ dual-ceramic coating," Surface and Coatings Technology, vol. 432, p. 128060, 2022.
[6]S. Kumar, S. Majumdar, B. Paul, J. Kishor and V. Kain, "Kinetics of formation of pack aluminized coating on 9Cr1Mo steel and interdiffusional behaviour of iron aluminides at intermediate temperatures," Surface and Coatings Technology, vol. 426, p. 127794, 2021.
[7]C. Wang, J. Lee and T. Twu, "Corrosion behaviors of low carbon steel, SUS310 and Fe–Mn–Al alloy with hot-dipped aluminum coatings in NaCl-induced hot corrosion," Surface and Coatings Technology, vol. 163, pp. 37-43, 2003.
[8]X. Chen, Q. Huang, Z. Yan, Y. Song, S. Liu and Z. Jiang, "Preliminary study of HDA coating on CLAM steel followed by high temperature oxidation," Journal of Nuclear Materials, vol. 442, no. 1-3, pp. S597-S602, 2013.
[9]K. Bouche, F. Barbier and A. Coulet, "Intermetallic compound layer growth between solid iron and molten aluminium," Materials Science and Engineering: A, vol. 249, no. 1-2, pp. 167-175, 1998.
[10]S. Kobayashi and T. Yakou, "Control of intermetallic compound layers at interface between steel and aluminum by diffusion-treatment," Materials science and engineering: A, vol. 338, no. 1-2, pp. 44-53, 2002.
[11]V. Yeremenko, Y. V. Natanzon and V. I. Dybkov, "The effect of dissolution on the growth of the Fe2Al5 interlayer in the solid iron-liquid aluminium system," Journal of Materials Science, vol. 16, no. 7, pp. 1748-1756, 1981.
[12]W. Qian, X. S. Leng, T.h. Yang and J. C. Yan, "Effects of Fe—Al intermetallic compounds on interfacial bonding of clad materials," Transactions of nonferrous metals society of China, vol. 24, no. 1, pp. 279-284, 2014.
[13]F. C. Yin, M. X. Zhao, Y. X. Liu, H. Wei and L. Zhi, "Effect of Si on growth kinetics of intermetallic compounds during reaction between solid iron and molten aluminum," Transactions of Nonferrous Metals Society of China, vol. 23, no. 2, pp. 556-561, 2013.
[14]P. Huilgol, K. U. Bhat and K. R. Udupa, "Hot-dip Aluminizing of Low Carbon Steel in Al & Al-5wt.% Cr Baths," Materials Today: Proceedings, vol. 5, no. 11, pp. 24702-24709, 2018.
[15]C. Su, J. Lee, C. Wang, C. Chao and T. Liu, "The effect of hot-dipped aluminum coatings on Fe-8Al-30Mn-0.8 C alloy," Surface and Coatings Technology, vol. 202, no. 9, pp. 1847-1852, 2008.
[16]W. J. Cheng and C. J. Wang, "Effect of chromium on the formation of intermetallic phases in hot-dipped aluminide Cr–Mo steels," Applied surface science, vol. 277, pp. 139-145, 2013.
[17]W. J. Cheng and C. J. Wang, "Study of microstructure and phase evolution of hot-dipped aluminide mild steel during high-temperature diffusion using electron backscatter diffraction," Applied Surface Science, vol. 257, no. 10, pp. 4663-4668, 2011.
[18]許芷寧，"碳鋼中顯微組織對熱浸鍍鋁之作用 "，國立臺灣科技大學機械工程系碩士論文，2012。
[19]P. Bindumadhavan, S. Makesh, N. Gowrishankar, H. K. Wah and O. Prabhakar, "Aluminizing and subsequent nitriding of plain carbon low alloy steels for piston ring applications," Surface and Coatings Technology, vol. 127, no. 2-3, pp. 251-258, 2000.
[20]N. Takata, M. Nishimoto, S. Kobayashi and M. Takeyama, "Crystallography of Fe2Al5 phase at the interface between solid Fe and liquid Al," Intermetallics, vol. 67, pp. 1-11, 2015.
[21]G. Eggeler, W. Auer and H. Kaesche, "On the influence of silicon on the growth of the alloy layer during hot dip aluminizing," Journal of Materials Science, vol. 21, no. 9, pp. 3348-3350, 1986.
[22]T. Heumann and S. Dittrich, "Über die Kinetik der Reaktion von festem und flüssigem Aluminium mit Eisen," International Journal of Materials Research, vol. 50, no. 10, pp. 617-625, 1959.
[23]X. Li, A. Scherf, M. Heilmaier and F. Stein, "The Al-rich part of the Fe-Al phase diagram," Journal of Phase Equilibria and Diffusion, vol. 37, no. 2, pp. 162-173, 2016.
[24]R. Yang, Q. Wu, S. Li and S. Gong, "Effects of Cr-Al-Si and Cr-Al coatings on the high temperature oxidation resistance of a Ni3Al-Mo based single crystal alloy," Procedia Engineering, vol. 27, pp. 976-982, 2012.
[25]M. Morris and D. Morris, "Quenching and ageing effects on defects and their structures in FeAl alloys, and the influence on hardening and softening," Scripta materialia, vol. 38, no. 3, pp. 509-516, 1998.
[26]M. Morris, O. George and D. Morris, "Vacancies, vacancy aggregates and hardening in FeAl," Materials Science and Engineering: A, vol. 258, no. 1-2, pp. 99-107, 1998.
[27]M. Montealegre, G. Strehl, J. L. González-Carrasco and G.Borchardt, "Oxidation behaviour of novel ODS FeAlCr intermetallic alloys," Intermetallics, vol. 13, no. 8, pp. 896-906, 2005.
[28]D. Hamana, L. Amiour and M. Bouchear, "Effect of chromium ternary additions on the ordering behaviour in Fe-28 at.% Al alloy," Materials Chemistry and Physics, vol. 112, no. 3, pp. 816-822, 2008.
[29]H. Okamoto, "Al-Cr (aluminum-chromium)," Journal of Phase Equilibria and Diffusion, vol. 29, no. 1, pp. 112-113, 2008.
[30]J. Wang, S. Liu, X. Bai, X. Zhou and X. Han, "Oxidation behavior of Fe–Al–Cr alloy at high temperature: Experiment and a first principle study," Vacuum, vol. 173, p. 109144, 2020.
[31]M. Hasegawa,"Ellingham diagram,"in Treatiseon Process Metallurgy: Elsevier, 2014, pp. 507-516.
[32]C. Xu and W. Gao, "Pilling-Bedworth ratio for oxidation of alloys," Material Research Innovations, vol. 3, no. 4, pp. 231-235, 2000.
[33]魏豐義, "金屬及合金在氧化中應力的生成及消除機構,"防蝕工程,vol. 1, no. 10, pp. 1-17, 1987.
[34]陳世明，"矽對鐵基與鎳基合金熱浸鋁化塗層之顯微結構和高溫氧化性的影響"，國立臺灣科技大學機械工程系博士論文，2007。
[35]Z. Liu and W. Gao, "Effects of chromium on the oxidation performance of β-FeAlCr coatings," Oxidation of metals, vol. 54, no. 3, pp. 189-209, 2000.
[36]B. Wu, E. Chang, C. Chao and M. Tsai, "The oxide pegging spalling mechanism and spalling modes of ZrO2 8 wt.% Y2O3/Ni-22Cr-10Al-1Y thermal barrier coatings under various operating conditions," Journal of Materials Science, vol. 25, no. 2, pp. 1112-1119, 1990.
[37]S. Kumar, A . Sourav, B . Murty , A . Chelvane and T . Shanmugasundaram, "Role of Al and Cr on cyclic oxidation behavior of AlCoCrFeNi2 high entropy alloy," Journal of Alloys and Compounds, p. 165820, 2022.