Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/9354
標題: 電解沉積氧化鋁陶瓷薄膜/無電鍍鎳在模具鋼SKD61之研究
The Study of Electrolytic Al2O3 Coating on Post Electroless Nickel Plating on SKD61 Mold Steel
作者: 何文賢
W.S.Ho
關鍵字: electrolytic Al2O3 coating;電解氧化鋁薄膜;electroless Nickel plating;SKD61 mold steel;無電鍍鎳;模具鋼
出版社: 材料工程學研究所
摘要: 
本實驗先用無電鎳方法在基材SKD61表面鍍上一層約5μm厚鎳磷合金,再使用電解沉積法於鎳合金上沉積氧化鋁陶瓷薄膜。氧化鋁陶瓷薄膜將藉著控制不同的電化學參數(溶劑、濃度、電位、時間),和不同的燒結條件,以決定出最佳之鍍膜製程條件,並利用恆定電位儀、SEM/EDS、XRD、磨耗試驗機、刮痕試驗機來探討各鍍層間之性質。
由陰極極化曲線發現;隨著電解液含水量減少,溶液中Al+3離子移動的阻力將變大,因此極化曲線會有往左移的趨勢,且愈有可能沉積出厚又不會產生裂痕的氧化鋁陶瓷薄膜。由XRD的結果發現:
(1) 電解硝酸鋁溶液後所得氧化鋁粉之相變化過程為
(2) 電解沉積氧化鋁陶瓷薄膜之相變化過程為
此差異性,係因氧化鋁水合物中含水量多寡所導致。
由循環極化結果可知;沉積氧化鋁薄膜後的試片,腐蝕電位、腐蝕電流及保護電位皆比Ni合金與基材SKD61佳,但沉積時間ta例外,因在孔腐之後薄膜會發生劈裂,所以保護電位會較低。
在荷重24.5N磨耗實驗中,將各條件下氧化鋁薄膜與鋁合金棒進行對磨,所得之重量損失皆比中間鍍層Ni合金及基材SKD61還小,且經計算氧化鋁膜的磨耗量最少者僅基材的1/28倍。
將氧化鋁膜進行刮痕實驗並做SEM/EDS,發現氧化鋁膜與無電鍍之附著力優於無電鍍鎳與基材SKD61,經計算無電鍍鎳約在2.23GPa的橫向剪應力下與基材剝離。

The electrolytic deposition of alumina(Al2O3) coatings on post electrolytic Ni deposited SKD61 was conducted in an aqueous solution of alumina-nitrate[Al(NO3)3]. The better condition of alumina coatings on Ni alloy was determined by controlling different electrical-chemical parameter (solvent
、concentration、potential、time) and different sintering conditions. The followed characterizations were conducted by using Potentiostat、SEM/EDS、XRD、wear test and scratch test.
From the left shifting of the polarization curves, it was known that the diffusing of Al+3 ions in solvent is decreased with decreasing water content in electrolyte. A thicker alumina-film without cracks can be deposited in the electrolyte containing less water.
XRD diagrams indicate that the phase transformations of alumina are
(1) for alumina-powder
(2) for alumina-film
The above difference between alumina-powder and alumina-film is controlled by the water-contained amount of alumina-hydrate.
Through the cycle polarization test in 3.5%NaCl, it was found that the corrosion potential、corrosion current and protection potential of both Al2O3 deposited specimens are better than Ni alloy and substrate, except ta deposited specimen which showed a lower protection potential due to the cleavage of Al2O3 films after pitting.
The wear tests with a load of 24.5N show that the wear loss of alumina-films by Al alloy pin is lower than both that of Ni and SKD61. The least one is only 1/28 of SKD61 substrates.
SEM/EDS observations and the scratch tests, revealed that Ni layer was first detached from SKD61 under shear stress of 2.23GPa. This also means that the adhesion between Al2O3 and Ni is better than that between Ni and SKD61.
URI: http://hdl.handle.net/11455/9354
Appears in Collections:材料科學與工程學系

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