表面改質對接合製程的影響

本研究分為兩部分，前半部分是將 MIM 純銅元件做高溫真空表面清潔，以清除試片表面碳汙染並讓氧化層還原，提高表面潔淨度後應可提升軟銲的潤濕性。後半部分是使用 Ti-15Cu-15Ni 填料分別將兩種鐵鉻合金(430SS 和 Crofer 22H)與Ti-15-3 合金真空接合。實驗中嘗試以濺鍍金屬層的方式隔絕 Fe 和 Ti 的反應，並改變基材與填料的組成，使銲道中的析出物固溶而消失。兩部分的實驗皆藉由 EPMA 方式鑑定各相元素組成比例，以驗證實驗結果。研究指出，將 MIM 純銅元件持溫於 400oC 以上半小時或是置於低/高真空半小時均可有效降低表面碳含量，已較未處理過的鍛件更低，若在高真空中持溫於400oC 半小時，表面碳含量則會降的更低。此外，氧化層在高真空中持溫於 600oC以上半小時後可被還原。兩種鐵鉻合金在鍍上 Cr 層後，接點產生的析出相並不產生變化。但若再鍍上一層 W 則會導致銲道產生相變化。由於 W 和 Cr 之熱膨脹係數不同，因此在升降溫的過程中導致 W 層破裂，無法阻擋填料與 Cr 層接觸。在 430SS 在先後鍍上 Cr 與 W 層之後，銲道中的 Ti2Ni 等析出物可逐漸被固溶，但界面產生 TiC 和Cr23C6 化合物；Crofer 22H 在界面上並沒有產生 TiC 和 Cr23C6 化合物，只憑藉 Cr層厚度無法阻擋 Fe 原子擴散，界面上仍可觀察到 Fe2Ti 等介金屬化合物。

關鍵字

表面改質；介金屬；真空； MIM ； 430SS ； Crofer22H

並列摘要

This study has two parts. The former part is conducting high temperature surface cleaning on pure copper MIM components to clean up carbon contaminations and to reduce oxide layer on surface. Wettability should be raised by improving surface cleanness. The latter part of this study is using Ti-15Cu-15Ni filler metal to braze two kinds of Fe-Cr alloys (430SS and Crofer 22H) and Ti-15-3 alloy in vacuum. Metal layers are sputtered to avoid reactions between Fe and Ti. Also, microstructures of Ti15-3 substrate and filler metal can be changed, intermetallic precipitates in the joint are dissolved. Atomic ratio of phases are identify by an EPMA in the experiments. Heating pure copper MIM components above 400oC and/or in low/high vacuum environment for half hour can effectively reduce MIM component’s surface carbon content comparable to that of wrought component. Surface carbon content can be even lower by heating MIM components above 400oC and in high vacuum environment at the same time. In addition, oxide layer can be reduced above 600oC in high vacuum environment. Phases in the joint remain unchanged after a Cr layer is sputtered on both kind of Fe-Cr alloys. However, if a W layer is further sputtered on the Cr layer, phase transformations occur in the joint. Since coefficients of thermal expansion of Cr and W are quite different, W layer breaks in the heating cycle, which causes filler metal could react with Cr layer. Intermetallics in the joint such as Ti2Ni can be dissolved after Cr and W layer are sputtered successively on 430SS alloy, but TiC and Cr23C6 compounds are found at the interface. TiC and Cr23C6 compounds are not found at the interface of Crofer 22H and Ti-15Cu-15Ni, diffusion of Fe atom can not be avoid by Cr layer only. Compounds like Fe2Ti are founded at the interface.