無電鍍鎳／氧化鋁與鎳／鑽石複合鍍層之腐蝕磨耗研究

Study on the Corrosive Wear Properties of Electroless Nickel / Al2O3 and Nickel / Diamond Composite Coatings

表面狀態是影響材料性質的重要因素之一，若能藉由表面改質的方式改善材料的耐蝕性及機械性質則可以提昇材料的使用壽命及安全係數。本研究利用無電鍍鎳法，在無電鍍鎳液中加入不同濃度與粒徑大小的陶瓷粉末（1μm與0.3μm）與不同粒徑的鑽石粉末（0 ~ 2μm與0 ~ 0.5μm）並鍍析於AISI 4140鋼基材上形成無電鍍鎳複合鍍層來改善基材的機械性質與抗蝕能力。鍍膜以塊對環（Block-on-ring）表面摩擦方式在3% NaCl溶液下分析鍍膜的抗腐蝕磨耗性，摩擦環為燒結氧化鋁（Al2O3）陶瓷，並且同時進行電化學腐蝕量測，且使用掃描式電子顯微鏡（SEM）來分析薄膜表面的形態。研究結果顯示研究結果顯示無電鍍鎳／氧化鋁複合鍍層均能增加AISI 4140鋼之腐蝕保護性，並會隨著氧化鋁粉末濃度的增加而增加，且會有一臨界飽和濃度16.65 g/L使耐腐蝕性達最大值，而氧化鋁粉的粒徑越小此最大耐腐蝕性越顯著並與無電鍍鎳1.67 g/L鑽石相當，當濃度超過此飽和濃度後鍍膜抗蝕能力則有下降趨勢。無電鍍鎳／氧化鋁複合鍍層之耐腐蝕磨耗對AISI 4140鋼基材也有明顯的改進效果，在濃度為10 g/L時顯示的耐腐蝕磨耗性可與濃度為1.67 g/L的無電鍍鎳鑽石相當。

The purpose of this study is to investigate the corrosion and corrosive wear resistance of electroless nickel composite coatings containing Al2O3 powder additive with different concentration (1 ~ 25 g/L) and diameter (1 μm and 0.3 μm), and also adding the diamond powder with different diameter (0 ~ 2 μm and 0 ~ 0.5 μm) for compared. Using a block-on ring surface friction method to evaluate the corrosive wear properties of these composite coatings in 3% NaCl solution. The friction ring counterpart is made of a sintered Al2O3. Electrochemical polarization measurements are performed for analyzing both corrosion and corrosive wear characteristics under static and wearing conditions, respectively. Surface morphologies and element compositions of the composite coatings before and after all tests are analyzed by scanning electron microscopy (SEM) and X-ray energy dispersive analyzer (EDS). The experimental results indicated that all the electroless nickel composite coatings posses a beneficial effect to improve the corrosion protection and corrosive wear resistance for the AISI 4140 steel substrate. The corrosion resistance of the composite coatings increases with increasing concentration of Al2O3 powder, and a critical concentration of 16.65 g/L with the maximum corrosion resistance is found, the maximum corrosion resistance value is more significant as less diameter of Al2O3 powder, also it is comparable with the diamond powder addition at a concentration of 1.67 g/L. The electroless nickel composite coating containing Al2O3 powder at concentration of 10 g/L exhibited the excellent corrosive wear resistance and its effect is comparable with the diamond powder addition at the concentration of 1.67 g/L.