本研究利用溶膠-凝膠法 (Sol-Gel Process)結合連續式雷射(Continuous-Wave Laser, CW Laser)於 Inconel 625 基板表面製備氧化鋁塗層，並探討掃描速度與循環次數對塗層表面形貌、相組成、元素分布、表面粗糙度、機械性質及摩擦磨耗性能之影響。
本研究利用光學顯微鏡 (OM)、X光繞射分析 (XRD)、掃描式電子顯微鏡搭配能量散射光譜儀 (SEM/EDS)、雷射掃描共軛焦顯微鏡、奈米壓痕試驗(Nanoindentation)及球盤式磨耗試驗 (Ball-on-Disk Wear Test)對塗層特性及性能進行分析與評估。
實驗結果顯示，在本研究所探討之所有加工條件下皆形成 α-Al2O3 結晶相。OM 觀察結果顯示，25 與 30 mm/s 條件下具有相對規則的表面形貌，而當掃描速度提高至 40 mm/s 時開始出現局部表面不規則現象，並於 50 mm/s 時更加明顯。30 mm/s 條件下之試片亦具有較 40 mm/s 低的表面粗糙度。EDS 元素分布與定量分析結果顯示，隨掃描速度增加，Al 含量整體呈增加趨勢，而 Ni 含量則降低。此外，30 mm/s、3次循環之試片之 O/Al 原子比最接近 Al2O3 的理論值 1.5。奈米壓痕結果顯示，氧化鋁塗層之平均硬度約介於 3.5–5.3 GPa，高於未處理 Inconel 625 基板約 2.5 GPa 的平均硬度。摩擦磨耗結果顯示，40 mm/s 條件下試片的平均摩擦係數整體低於 30 mm/s。所有氧化鋁塗層試片的磨耗率皆明顯低於未塗層基板，其平均磨耗率約介於 4.3 × 10-3 至 5.3 × 10-3 mm3/N·m，而未塗層基板約為 14.1 × 10-3 mm3/N·m。
綜合實驗結果可知，溶膠凝膠結合連續波雷射製程可成功於 Inconel 625 基板上形成 α-Al2O3 結晶塗層，並改善其機械性質與耐磨耗性能。雖然將掃描速度提高至 40 mm/s 可獲得相對較低的摩擦係數與磨耗率，但同時伴隨著表面不規則程度增加與表面粗糙度上升。因此，在本研究所探討的製程範圍內，30 mm/s 在表面品質與功能性表現之間提供了較佳的平衡。

In this study, alumina coatings were fabricated on Inconel 625 substrates using a sol–gel process combined with continuous-wave (CW) laser treatment. The effects of scanning speed and number of cycles on the surface morphology, phase composition, elemental distribution, surface roughness, mechanical properties, and tribological performance of the coatings were investigated.
The coatings were characterized using optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM/EDS), laser scanning confocal microscopy, nanoindentation, and ball-on-disk wear tests to evaluate the coating characteristics and properties.
The experimental results confirmed the formation of crystalline α-Al2O3 under all investigated processing conditions. OM observations showed that relatively regular surface morphologies were obtained at 25 and 30 mm/s, whereas localized surface irregularities began to appear at 40 mm/s and became more pronounced at 50 mm/s. The specimens processed at 30 mm/s also exhibited lower surface roughness than those processed at 40 mm/s. EDS elemental mapping and quantitative analysis showed that increasing the scanning speed generally resulted in higher Al content and lower Ni content. In addition, the specimen processed at 30 mm/s with 3 cycles exhibited an O/Al atomic ratio closest to the theoretical value of 1.5 for Al2O3. Nanoindentation results showed that the average hardness of the alumina coatings ranged from approximately 3.5 to 5.3 GPa, which was higher than that of the untreated Inconel 625 substrate at approximately 2.5 GPa. The tribological results showed that the specimens processed at 40 mm/s generally exhibited lower average coefficients of friction than those processed at 30 mm/s. All alumina-coated specimens exhibited substantially lower wear rates than the uncoated substrate, with average wear rates ranging from approximately 4.3 × 10-3 to 5.3 × 10-3 mm3/N·m, compared with approximately 14.1 × 10-3 mm3/N·m for the substrate.
Overall, the results demonstrate that the combined sol–gel and CW laser process successfully produced crystalline α-Al2O3 coatings on Inconel 625 substrates and improved their mechanical and wear properties. Although increasing the scanning speed to 40 mm/s resulted in relatively lower coefficients of friction and wear rates, it was accompanied by increased surface irregularities and higher surface roughness. Therefore, 30 mm/s provided a favorable balance between surface quality and functional performance within the investigated processing range.

[1] Dinesh Babu, P., K.R. Balasubramanian, and G. Buvanashekaran, Laser surface hardening: a review. International Journal of Surface Science and Engineering, 2011. 5(2-3): p. 131-151. https://doi.org/10.1504/IJSURFSE.2011.041398.
[2] Dutta Majumdar, J. and I. Manna, Laser material processing. International Materials Reviews, 2011. 56(5-6): p. 341-388. https://doi.org/10.1179/1743280411Y.0000000003.
[3] McDaniels, R.L., S.A. White, K. Liaw, L. Chen, M.H. McCay, and P.K. Liaw, Effects of a laser surface processing induced heat-affected zone on the fatigue behavior of AISI 4340 steel. Materials Science and Engineering: A, 2008. 485(1): p. 500-507. https://doi.org/10.1016/j.msea.2007.08.039.
[4] Gnanamuthu, D.S., Laser Surface Treatment. Optical Engineering, 1980. 19(5): p. 195783. https://doi.org/10.1117/12.7972604.
[5] Kwok, C.T., F.T. Cheng, and H.C. Man, Laser surface modification of UNS S31603 stainless steel. Part I: microstructures and corrosion characteristics. Materials Science and Engineering: A, 2000. 290(1): p. 55-73. https://doi.org/10.1016/S0921-5093(00)00929-1.
[6] de Damborenea, J., Surface modification of metals by high power lasers. Surface and Coatings Technology, 1998. 100-101: p. 377-382. https://doi.org/10.1016/S0257-8972(97)00652-X.
[7] Rickerby, D.S. and S.J. Bull, Engineering with surface coatings: The role of coating microstructure. Surface and Coatings Technology, 1989. 39-40: p. 315-328. https://doi.org/10.1016/0257-8972(89)90065-0.
[8] Wood, R.J., Tribo-corrosion of coatings: a review. Journal of Physics D: Applied Physics, 2007. 40(18): p. 5502-5521.https://doi.org/10.1088/0022-3727/40/18/S10.
[9] Ching, H.A., D. Choudhury, M.J. Nine, and N.A. Abu Osman, Effects of surface coating on reducing friction and wear of orthopaedic implants. Science and technology of advanced materials, 2014. 15(1): p. 014402. https://doi.org/10.1088/1468-6996/15/1/014402.
[10] Van Stappen, M., L. Stals, M. Kerkhofs, and C. Quaeyhaegens, State of the art for the industrial use of ceramic PVD coatings. Surface and Coatings Technology, 1995. 74: p. 629-633. https://doi.org/10.1016/0257-8972(95)08296-4.
[11] Rebenne, H.E. and D.G. Bhat, Review of CVD TiN coatings for wear-resistant applications: deposition processes, properties and performance. Surface and Coatings Technology, 1994. 63(1): p. 1-13. https://doi.org/10.1016/S0257-8972(05)80002-7.
[12] Dehghanghadikolaei, A., J. Ansary, and R. Ghoreishi, Sol-gel process applications: A mini-review. Proc. Nat. Res. Soc, 2018. 2(1): p. 02008-02029. https://doi.org/10.11605/j.pnrs.201802008.
[13] Zanurin, A., N. Johari, J. Alias, H.M. Ayu, N. Redzuan, and S. Izman, Research progress of sol-gel ceramic coating: A review. Materials today: proceedings, 2022. 48: p. 1849-1854. https://doi.org/10.1016/j.matpr.2021.09.203.
[14] Karmakar, R., P. Maji, and S.K. Ghosh, A Review on the Nickel Based Metal Matrix Composite Coating. Metals and Materials International, 2021. 27(7): p. 2134-2145. https://doi.org/10.1007/s12540-020-00872-w.
[15] Wang, D. and G.P. Bierwagen, Sol–gel coatings on metals for corrosion protection. Progress in Organic Coatings, 2009. 64(4): p. 327-338. https://doi.org/10.1016/j.porgcoat.2008.08.010.
[16] Abidin, M.Z.U., M. Ikram, S. Moeen, G. Nazir, M.B. Kanoun, and S. Goumri-Said, A comprehensive review on the synthesis of ferrite nanomaterials via bottom-up and top-down approaches advantages, disadvantages, characterizations and computational insights. Coordination Chemistry Reviews, 2024. 520: p. 216158. https://doi.org/10.1016/j.ccr.2024.216158.
[17] Chen, Y.-C., X. Ai, C.-Z. Huang, and B.-Y. Wang, Preparation of α-alumina coated carbide tools by the sol-gel process. Materials Science and Engineering: A, 2000. 288(1): p. 19-25. https://doi.org/10.1016/S0921-5093(00)00840-6.
[18] Taylor, D.J. and B.D. Fabes, Laser processing of sol-gel coatings. Journal of Non-Crystalline Solids, 1992. 147-148: p. 457-462. https://doi.org/10.1016/S0022-3093(05)80658-1.
[19] Adraider, Y., Y.X. Pang, F. Nabhani, S.N. Hodgson, M.C. Sharp, and A. Al-Waidh, Laser-induced deposition of alumina ceramic coating on stainless steel from dry thin films for surface modification. Ceramics International, 2014. 40(4): p. 6151-6156. https://doi.org/10.1016/j.ceramint.2013.11.067.
[20] Adraider, Y., Y.X. Pang, F. Nabhani, S.N. Hodgson, and Z.Y. Zhang, Laser-induced deposition of sol–gel alumina coating on stainless steel under wet condition. Surface and Coatings Technology, 2011. 205(23): p. 5345-5349. https://doi.org/10.1016/j.surfcoat.2011.05.044.
[21] Iqbal, M.A., K. Skotnicová, A. Shafiq, and T.N. Sindhu, Inconel alloys: A comprehensive review of properties and advanced manufacturing techniques. International Journal of Thermofluids, 2025. 29: p. 101394. https://doi.org/10.1016/j.ijft.2025.101394.
[22] de Oliveira, M.M., A.A. Couto, G.F.C. Almeida, D.A.P. Reis, N.B. de Lima, and R. Baldan Mechanical Behavior of Inconel 625 at Elevated Temperatures. Metals, 2019. 9, 301 https://doi.org/10.3390/met9030301.
[23] Sharifitabar, M., S. Khorshahian, M. Shafiee Afarani, P. Kumar, and N.K. Jain, High-temperature oxidation performance of Inconel 625 superalloy fabricated by wire arc additive manufacturing. Corrosion Science, 2022. 197: p. 110087. https://doi.org/10.1016/j.corsci.2022.110087.
[24] Wang, C., J. Liu, K. Zhang, X. Yi, H. Long, W. Sun, Z. Liu, and G. Wang, Oxidative wear behaviors of Inconel 625 alloy in a simulated rotary calcination furnace environment at 600 and 800 ℃. Tribology International, 2024. 200: p. 110133. https://doi.org/10.1016/j.triboint.2024.110133.
[25] Ulutan, D. and T. Ozel, Machining induced surface integrity in titanium and nickel alloys: A review. International Journal of Machine Tools and Manufacture, 2011. 51(3): p. 250-280. https://doi.org/10.1016/j.ijmachtools.2010.11.003.
[26] Poloczek, T., A. Lont, and J. Górka The Structure and Properties of Laser-Cladded Inconel 625/TiC Composite Coatings. Materials, 2023. 16, 1265 10.3390/ma16031265.
[27] Chen, T.-C., C.-C. Chou, H.-E. Lin, T.-Y. Yung, C.-T. Yang, and Y.-W. Tsai, Influence of coating microstructure on the corrosion behavior of Inconel 625 coatings fabricated by different thermal spraying processes. Surface and Coatings Technology, 2024. 484: p. 130674. https://doi.org/10.1016/j.surfcoat.2024.130674.
[28] Fantozzi, D., V. Matikainen, M. Uusitalo, H. Koivuluoto, and P. Vuoristo, Chlorine-induced high temperature corrosion of Inconel 625 sprayed coatings deposited with different thermal spray techniques. Surface and Coatings Technology, 2017. 318: p. 233-243. https://doi.org/10.1016/j.surfcoat.2016.12.086.
[29] Abioye, T.E., D.G. McCartney, and A.T. Clare, Laser cladding of Inconel 625 wire for corrosion protection. Journal of Materials Processing Technology, 2015. 217: p. 232-240. https://doi.org/10.1016/j.jmatprotec.2014.10.024.
[30] Xu, X., G. Mi, L. Chen, L. Xiong, P. Jiang, X. Shao, and C. Wang, Research on microstructures and properties of Inconel 625 coatings obtained by laser cladding with wire. Journal of Alloys and Compounds, 2017. 715: p. 362-373. https://doi.org/10.1016/j.jallcom.2017.04.252.
[31] Daure, J.L., K.T. Voisey, P.H. Shipway, and D.A. Stewart, The effect of coating architecture and defects on the corrosion behaviour of a PVD multilayer Inconel 625/Cr coating. Surface and Coatings Technology, 2017. 324: p. 403-412. https://doi.org/10.1016/j.surfcoat.2017.06.009.
[32] Zhang, Z., Y. Pan, H. Guo, X. Zeng, Q. Shi, and T. Lu Fabrication and Supercritical Water Corrosion Resistance of TiN/TiNC/Al2O3 Multilayer Coating on Inconel 625 Alloy by CVD Method. Materials, 2022. 15, 7670 https://doi.org/10.3390/ma15217670.
[33] Dosta, S., N. Cinca, A. Silvello, and I.G. Cano Alumina Reinforcement of Inconel 625 Coatings by Cold Gas Spraying. Metals, 2020. 10, 1263 https://doi.org/10.3390/met10091263.
[34] Pantelis, D.I., P. Psyllaki, and N. Alexopoulos, Tribological behaviour of plasma-sprayed Al2O3 coatings under severe wear conditions. Wear, 2000. 237(2): p. 197-204. https://doi.org/10.1016/S0043-1648(99)00324-5.
[35] de Arellano-López, A.R. and K.T. Faber, Microstructural Characterization of Small-Particle Plasma Spray Coatings. Journal of the American Ceramic Society, 1999. 82(8): p. 2204-2208. https://doi.org/10.1111/j.1151-2916.1999.tb02063.x.
[36] Wilson, S., H.M. Hawthorne, Q. Yang, and T. Troczynski, Sliding and abrasive wear of composite sol–gel alumina coated Al alloys. Surface and Coatings Technology, 2000. 133-134: p. 389-396. https://doi.org/10.1016/S0257-8972(00)00964-6.
[37] Kaur, P., A. Khanna, N. Kaur, P. Nayar, and B. Chen, Synthesis and structural characterization of alumina nanoparticles. Phase Transitions, 2020. 93(6): p. 596-605. https://doi.org/10.1080/01411594.2020.1765245.
[38] Lux, B., C. Colombier, H. Altena, and K. Stjernberg, Preparation of alumina coatings by chemical vapour deposition. Thin Solid Films, 1986. 138(1): p. 49-64. https://doi.org/10.1016/0040-6090(86)90214-2.
[39] Bandyopadhyay, P.P., D. Chicot, B. Venkateshwarlu, V. Racherla, X. Decoopman, and J. Lesage, Mechanical properties of conventional and nanostructured plasma sprayed alumina coatings. Mechanics of Materials, 2012. 53: p. 61-71. https://doi.org/10.1016/j.mechmat.2012.05.006.
[40] Livage, J., Sol-gel processes. Current Opinion in Solid State and Materials Science, 1997. 2(2): p. 132-138. https://doi.org/10.1016/S1359-0286(97)80057-5.
[41] Adraider, Y., Y.X. Pang, F. Nabhani, S.N. Hodgson, M.C. Sharp, and A. Al-Waidh, Fabrication of zirconium oxide coatings on stainless steel by a combined laser/sol–gel technique. Ceramics International, 2013. 39(8): p. 9665-9670. https://doi.org/10.1016/j.ceramint.2013.05.089.
[42] Schuh, C.A., Nanoindentation studies of materials. Materials Today, 2006. 9(5): p. 32-40. https://doi.org/10.1016/S1369-7021(06)71495-X.
[43] Yang, Z.-Q., H.-M. Kuo, H.-C. Chiang, and C.-H. Hung, Enhanced wear resistance of low carbon steel by depositing iron-chromium alloy coating using high-power laser cladding. The International Journal of Advanced Manufacturing Technology, 2025. 137(3): p. 1133-1147. https://doi.org/10.1007/s00170-025-15271-x.