以液態原子力顯微鏡即時觀察合金薄膜剝除行為之研究

Investigation into the Stripping Behavior of Alloy Coatings by In-situ Liquid Mode Atomic Force Microscope

近年來在壓製光學鏡片模具表面常常披覆硬質薄膜以增強其機械性質並延長使用壽命。但隨著高溫環境長時間的使用，薄膜開始產生損壞而導致機械性質下降與表面粗糙度劣化，因此必須將損壞之薄膜剝除。本研究將以液態原子力顯微鏡於水溶液環境中即時觀察Mo-Ru硬質合金薄膜剝除過程，再利用SEM觀察剝除薄膜之後的試片表面形貌，並使用XRD與EDS分析試樣表面之晶相與成分變化。本研究發現在進行剝膜試驗初始階段時，有細小蝕孔在薄膜表面缺陷產生，隨著鉻中間層被腐蝕液侵蝕，薄膜表面開始產生裂縫，並隨著時間的增加，薄膜開始產生剝落與翹曲變形是由於薄膜之殘留應力所致，另一方面純鈦中間層可以保護碳化鎢基材避免受到蝕刻液的侵蝕。

Hard coating materials are widely used in glass molding industries to prolong the lifetime and to enhance the mechanical properties of molding dies. The coating on the surface of a molding die in service could actually undergo both a cyclic thermal aging treatment and a high temperature oxidation process, which would lead to degradation in mechanical property and surface roughness of the coated die. To remove a failed coating resulted from service damage is therefore as important as to deposit it on the molding die. An Mo-Ru hard coating was deliberately stripped from a tungsten carbide substrate in an etching solution and the stripping process was monitored by the in-situ liquid mode atomic force microscope. The surface morphologies were analyzed by SEM, and the chemical composition and phases were evaluated by XRD and EDS. It was found that pits formed on the Mo-Ru hard coating through surface defect sites in the beginning, followed by the attack of the etchant to Cr interlayers. Accordingly, the Mo-Ru coating cracked and delaminated due to the residual stress and the accumulation of the etching products. On the other hand, the Ti interlayer was still effective to protect the tungsten carbide substrate from the attack of the etchant.