粉末冶金法製作Cu/SiC放電加工用電極材料

Abstract

一般放電加工(Electric Discharge Machining)用純銅電極因切削性差 ，且在高溫下會因高膨脹係數而有較大的尺寸變化，因此本研究使用粉末 冶金的技術在銅中混入SiC形成Cu/SiC金屬基複合材料以克服上述缺點。 SiC能在銅中形成散佈強化，對某些機械性質提升有所助益，而要達到此 一效果的主要關鍵受Cu/SiC間鍵結良否與燒結溫度所控制。經由無電鍍銅 法在SiC表面鍍上一層銅薄膜予以活化，可使SiC顆粒與銅基地有良好的鍵 結。燒結溫度的選擇則必須考慮避免銅與SiC產生還原反應的影響。本實 驗將比對無電鍍與電鍍對燒結物顆粒間鍵結的影響，同時以三種燒結溫 度850℃、950℃、1000℃來比對燒結條件對1wt%與5wt%Cu/SiC複合材料的 影響。將這些不同條件的燒結品進行機械性質如強度、硬度、伸長量、放 電磨耗比等測量。所有情況皆顯示經鍍銅活化處理SiC形成的複合材料會 比未處理者好。在燒結溫度上，一般而言隨著溫度增加，各項性質也會有 所提升，但當達1000℃時，若複合材料為高含量SiC，過量的還原反應將 導致機械性質的降低。 In general, The copper electrode used in electrical discharge machining(EDM) is difficult to form by cutting, and its dimension will also be expanded to a large extent at high temperature.Therefore,a Cu/SiC metal-matrix composite (MMC) made by powder metallurgy(P/M) method was tried in this work to overcome these drawbacks.It is reckoned that some mechanical properties can be improved due to the disperison strengthening effectof SiC in copper.The governing factors to achieve this object are the bonding condition between copper and SiC and the sintering temperature.It was found that an improved bonding can be obtained through activation of SiC powder surface by electroless-coating of copper on it.The present work investigated the effect of copper coating on the sintered bonding property. Also, three sintering temperatures, 850℃、950 ℃ and 1000℃, were performed on 1wt％SiC and 5wt％SiC composite materials to study the temperature effect. The mechanical (strength, hardness, elongation and density) and electrical (wear ratio) properties were measured. Results showedthat much better properties can be attained with Cu-coating-SiC. Generally,the properties is improved as sintering temperature increas