本文探討添加不同比例稀土元素(氧化鈰與氧化釔)，對於SKD61模具鋼表面氬銲被覆多元合金(NiAlTiCoW)被覆層之顯微結構與磨耗行為的影響。並找出影響耐磨耗能力之主要關鍵，以做為SKD61模具鋼表面耐磨耗改質的依據。
研究結果顯示，NiAlTiCoW系列之被覆層均屬於析出強化型機構。添加氧化鈰(CeO)、氧化釔(Y2O3)皆會細化被覆層內的析出強化相。當添加1%的氧化鈰，會使被覆層內的W元素散佈到基地內，導致樹狀晶強化相消失，進而使硬度下降。而添加1.0% Y2O3會降低被覆層稀釋區範圍，導致被覆層的Fe元素含量降低，進而使Fe溶液所能固溶的W元素含量大幅度減少，因此使白色顆粒狀純W析出物變多。
在磨耗實驗結果當中發現，以無添加稀土元素的NiAlTiCoW的被覆層效果最佳，而添加稀土元素CeO與Y2O3，對於被覆試片的耐磨耗性並無明顯的改善，這可能是因為被覆層內的強化相析出物被過度細化所導致。

In this work, an equimolar powder mixture of NiAlTiCoW with different contents of rare earth elements (CeO and Y2O3) was clad on the surface of the SKD61 tool steel using GTAW method. The effects of CeO and Y2O3 on microstructure and wear behavior of the NiAlTiCoW multicomponent clad layer were investigated. Additionally, the major factors that influence wear performance of the clad layers were found out.
　　Experimental results show that the NiAlTiCoW clad layer is strengthened by the different precipitates. The addition of CeO and Y2O3 can refine the precipitates. When the addition of CeO is 1 wt.%, the W element is distributed in the matrix, resulting in the disappearance of dendritic reinforcement and the decrease in hardness. When the addition of Y2O3 is 1 wt.%, the dilution zone is reduced, resulting in the decrease in content of Fe element. This can decrease the content of W element dissolved into Fe-liquid. Therefore, the W precipitates with white granular structure are increased.
　　The wear test results indicate that the wear performance of the NiAlTiCoW clad layer without rare earth elements is better than that of the NiAlTiCoW clad layer with rare earth elements. This is attributed to the over-refined precipitates in the clad layers.

1. K. N. Strafford, P. K. Datta, J. S. Gray,Surface Engineering Practive, 1990.
2. K. Holmberg, A. Matthews, Coatings tribology, Amsterdam, Elsevier, 1994.
3. J. W. Giachino，Welding skills and practices，1986.
4. G. B. Kenneth，Surface Engineering for wear Resistance.
5. J. F. Lancaster, Metallurgy of welding, London, Chapman & Hall, 1993.
6. Jien-Wei Yeh, Swe-Kai Chen, Su-Jien Lin, Jon-Yiew Gan, Tsung-Shune Chin, Tao-Tsung Shun, Chun-Huei Tsau, and Shou-Yi Chang, “Nanostructured High-Entropy Alloys with Multiple Principal Elements: Novel Alloy Design Concepts and Outcomes”, Advanced Engineering Meterials , No. 5, pp. 299-303 ,2004.
7. J.W. Yeh, S.K. Chen, J.Y. Gan, S.J. Lin, T.S. Chin, T.T. Shun, C.H. Tsau, S.Y. Chang, Formation of simple crystal structures in Cu-Co-Ni-Cr-Al-Fe- Ti-V alloys with multiprincipal metallic elements, Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, v 35 A, n 8, August, 2004, pp. 2533-2536.
8. Y.J. Zhou, Y. Zhang, Y.L. Wang, G.L. Chen, Microstructure and compressive properties of multicomponent Alx(TiVCrMnFeCoNiCu)100-x high-entropy alloys, Materials Science and Engineering A, v 454-455, Apr 25, 2007, pp. 260-265.
9. X.F. Wang, Y. Zhang, Y. Qiao, Novel microstructure and properties of multicomponent CoCrCuFeNiTix alloys, Intermetallics, v 15, n 3, March, 2007, pp.357-362.
10. B. Cantor, I.T.H. Chang, P. Knight, A.J.B. Vincent, Microstructural development in equiatomic multicomponent alloys, Materials Science and Engineering A, v 375-377, n 1-2 SPEC. ISS., Jul 15, 2004, pp.213-218.
11. J.M.Wu, S.J.Lin, J.W.Yeh, S.K.Chen, Y.S.Huang, H.C.Chen, Adhesive wear behavior of AlxCoCrCuFeNi high-entropy alloys as a function of aluminum content, Wear, v 261, n 5-6, Sep 20, 2006, pp.513-519.
12. C.H.Tung, J.W.Yen, T.T.Shun, S.K.Chen, Y.S.Huang, H.C.Chen, On the elemental effect of AlCoCrCuFeNi high-entropy alloy system, Materials Letters, v 61, n 1, January, 2007, pp.1-5.
13. Yanfang Wang, Gang Li, Cunshan Wang, Yuanliang Xia, Bysakh Sandip, Chuang Dong, “Microstructure and properties of laser clad Zr-based alloycoatings on Tisubstrates” ,Surface and Coatings Technology 176 ,pp. 284- 289,2004.
14. Y.Chen, H.M.Wang, “Microstructure and wear resistance of a laser clad TiC reinforced nickel aluminides matrix composite coating”,Materials Science and Engineering A368 ,2004, pp.80-87.
15. Xiaolei Wu, Youshi Hong,“ Fe-based thick amorphous-alloy coating by laser cladding”,Surface and Coatings Technology141,2001 , pp.141–144.
16. Z.Werner, J.Stanislawski, J.Piekoszewski, E.A. Levashov, W Szymczyk, “New types of multi-component hard coatings deposited by ARC PVD on steel pre-treated by pulsed plasma beams”,Vacuum 70 ,2003 , pp.263-267.
17. 錢景常譯 , 「稀土族十五個元素」 , 原子能文庫/鄭振華 主編1969.

18.
W. Maocai, Y. Yonggen, W. Weitao, Z. Jingpu, Effect of Yttrium on microstructure and hot corrosion performance of laser clad Co-Based alloy, Journal of the Chinese Rare Earth Society (English Edition) ,1993, pp.278-282.
19. W. Weitao, Microstructure of laser-surface-alloyed cast iron with Cr-Al-Y alloy, Surface & Coatings Technology 72 ,1995, pp.181-188.
20. Y. Yongqiang, Existent forms and effects of yttrium in laser claddings of MCrAlY, Journal of South China University of Technology (Natural Science) 26 ,1998, pp.65-68.
21. K.L Wang, Q.B. Zhang, M.L. Sun, X.G. Wei, Microstrural characteristics of laser clad coatings with rare earth metal elements, Journal of Processing Technology 139,2003, pp.448-452.
22. L. Jiajun, Z. Baoliang, Effect of rare-earth elements on the wear resistance of iron base thermal spray-welding coating and its mechanism, Mocaxue Xuebao/Tribology, 14 ,1994, pp.298-305.
23. K. L. Wang, Y. M. Zhu, Q. B. Zhang, M. L. Sun, Effect of rare-earth cerium on the microstructure and corrosion resistance of laser cladded nickel-base alloy coatings, Journal of Materials Processing Technology 63 ,1997, pp.563-567.
24. L.Zhang, D.Sun, H.Yu, Characteristics of plasma cladding Fe-based alloy coatings with rare earth metal elements, Materials Science and Engineering A, v 452-453, Apr 15, 2007, pp.619-624.
25. 李明奇，製程參數對中碳鋼表面被覆SiC粉末耐磨耗性能之影響，國立台灣科技大學碩士論文，1998.
26. 劉國雄、林樹均、李勝隆、鄭晃忠、葉鈞蔚 , 工程材料科學 , 全華科技圖書股份有限公司 ,1996.
27. G. E. Dieter, Mechanical metallurgy, London, McGraw-Hill, 1988.
28. H. Sin, N. Saka, N. P. Suh, Abrasive wear mechanisms and the grit size effect, Wear 55 ,1979, pp.163-190.
29. G. W. Stachowiak, A. W. Batchelor, Engineering tribology, Amsterdam, Elsevier, New York ,1993.
30. C. Horst, Tribology : a systems approach to the science and technology of friction, lubrication and wear, Amsterdam, Elsevier Scientific Pub. Co., New York ,1978.
31. V. V. Pokropivny, V. V. Skorokhod, A. V. Pokropivny, Atomistic mechanism of adhesive wear during friction of atomic-sharp tungsten asperity over (114) bcc-iron surface, Materials letters 31 ,1997, pp.49-54.
32. Markov. D, Kelly. D, Mechanisms of adhesion-initiated catastrophic wear: pure sliding, Wear 239,2000, pp.189-210.
33. T. F. J. Quinn, J. L. Sullivan, D. M. Rowson, Origins and development of oxidational wear at low ambient temperatures, Wear 94,1984, pp.175-191.
34. T. F. J. Quinn, W. O. Winer, An experimental study of the “hot-spots” occurring during the oxidational wear of tool steel on sapphire, Journal of Tribology 109 ,1987, pp.315-320.
35. Vardavoulias. M, The role of hard second phases in the mild oxidational wear mechanism of high-speed steel-based materials, Wear 173 ,1994, pp.105-114.

36.
T. F. J. Quinn, Computional methods applied to oxidational wear, Wear 199 ,1996, pp.169-180.
37. T. F. J. Quinn, Oxidational wear modeling part Ⅲ. The effects of speed and elevated temperatures, Wear 216 ,1998, pp.262-275.
38. T. F. J. Quinn, The oxidational wear of low alloy steels, Tribology International 35 ,2002, pp.691-715.
39. J. M. Guilemany, J. M. Miguel, S. Vizcaino, F. Climent, Role of three-body abrasion wear in the sliding wear behaviour of WC-Co coatings obtained by thermal spraying, Surface and Coatings Technology 140,2001, pp.141-146.
40. H. So, The mechanism of oxidational wear, Wear 184,1995, pp.161-167.
41. N. P. Suh, The delamination theory of wear, Wear 25 ,1973, pp.111-124.
42 Jahanmir. S, N. P. Suh, E. P. Abrahamson, Microscopic observations of the wear sheet formation by delamination, Wear 28,1974, pp.235-249.
43. Bhushan , Bharat , Handbook of Tribology , McGraw-Hill , USA , 1991.
44. Y. C. Lin, S. W. Wang, Wear behavior of ceramic powder cladding on an S50C steel surface, Tribology International 36,2003, pp.1-9.
45. X. H. Wang, S. L. Song, S. Y. Qu,Z. D. Zou, Characterization of in situ synthesized TiC particle reinforced Fe-based composite coatings produced by multi-pass overlapping GTAW melting process, Surface and Coatings Technology 201,2007, pp.5899-5905.
46. Z. Li , Effects of rare-earth element on structure and abrasion resistance of alloy powder spray welding coating, Cailiao Gongcheng/Journal of Materials Engineering, n 3, 1993, pp.9-12.
47. Y. S. Tian, C. Z. Chen, L. X. Chen, Q. H. Huo, Effect of RE oxides on the microstructure of the coatings fabricated on titanium alloys by laser alloying technique, Scripta Materialia 54,2006, pp.847-852.
48 Xuan .Tianpeng, Dan. Min, Effect of rare earth on microstructure of vacuum melting Ni-based self-fluxing alloy coatings, Journal of Rare Earths, v 22, n 4, August, 2004, pp.517-520.