鎳基納米級碳化矽粉末之複合電鍍

Abstract

複合鍍層幾十年來已做了許多研究，其應用性也多受重視，其中最為人所熟知的莫若是陶瓷汽缸引擎的發展，另外亦有人應用在封裝模具上，其目的在提升其耐磨耗性，增加使用效能及其壽命。而關於複合鍍的研究多著重於沈積機構的探討或性能的提升上，鮮少對其顯微結構及電化學性質作一深入的解析，本研究即針對此兩點配合機械性質進行納米級強化複合電鍍的探討。 本實驗採用氨基磺酸鎳浴，加入「納米級」碳化矽（SiC）陶瓷粒子，控制pH值、溫度以及攪拌環境為一定值，而改變的參數為電流密度及粉末含量。對各參數變化下所得的複合鍍層進行各項檢測，包括機械性質、表面形貌、顯微結構以及電化學分析等。 由實驗結果可知，其硬度及耐磨耗性得到明顯地提升，其中硬度值隨電鍍中所添加的粉末含量增加而變大，而磨耗試驗之重量損失亦隨添加之SiC粉末而下降；在電化學方面，腐蝕電位、臨界電位以及臨界電流皆有不同的變化表現；在表面形貌方面，複合鍍層表面呈現不規則突起，藉表面粗度測試及掃描式電子顯微鏡進行觀察分析；在顯微結構方面，由掃瞄式電子顯微鏡及穿透式電子顯微鏡鍍層組織及其微結構，配合EDX能譜分析可清楚觀察SiC在鍍層中的分佈狀況。

Lots of researches on composite electrodeposition have been made in recent years. The applications in ceramic piston engine and die packing are well-known ones; these applications aims to promote wear resistance、usage efficiency and hence increase lifetime. Previous works often concentrate in the deposition mechanism and the promotion of property. There are paucity of researches concerning the microstructure and electrochemical property of the deposited layer. This thesis aims to study the two aspects, together with the mechanical properties, of the coating layer formed by composite electroplating of nickel with nano-SiC ceramic powder. The study employed nickel sulfamate bath added with nano-SiC powder. The pH、temperature and stirring condition were fixed and the current density and concentration of powder were varied. Then the mechanical property、morphology、microstructure and electrochemical property of deposited layer were investigated. Results indicated that the hardness and wear resistance were apparently improved. The hardness increased and the weight loss of wear test decreased with the content of powder in the bath. In electrochemical analysis, the corrosion potential、critical potential and passivation current density of variously formed coating performed differently. In the morphology, the irregular prominence on the composite coating surface was observed by roughness measurement and SEM observation. In the microstructure, the distribution of nano-SiC powder in the composite coatings were identified using SEM、TEM and EDX techniques.