氧化鈣含量對氧化鈣/氧化鋯系陶瓷材料與熔融鈦介面反應的影響

Abstract

一般鈦合金之精密鑄造係採用電弧熔融法（vacuum arc melting, VAR, 一名 skull melting, 骸式熔融法），以水冷式銅坩鍋盛裝鈦融液，在坩鍋壁上產生凝固 層，以保護銅坩鍋，惟此法的液態鈦金屬流動性不良，故多以離心鑄造法進行鈦 合金之鑄造。鈦金屬在熔融時是一種活性極強的金屬，直接與陶瓷模接觸，易在 介面發生劇烈反應，產生表面硬化層，常是鑄件產生裂縫成長的起始點。因此， 一般在鑄件完成後會以化學溶液洗蝕或噴砂法除去表面硬化層，如此不僅增加成 本，亦影響鑄件精密度。欲選用最適合的坩堝與陶模材料應用於精密鑄造，應先 瞭解鈦合金與陶瓷的介面反應，並有效控制之。 本實驗室過去已研究氧化鋯與鈦金屬的介面反應機構，並探討氧化釔含量對 介面反應的影響，有非常重要的成果發表於美國陶瓷學會期刊上。本實驗將研究 CaO/ZrO2 系陶瓷材料與高溫熔融鈦金屬的介面反應。以x-ray 繞射儀、熱場發射 掃瞄式電子顯微鏡及能量分散能譜儀（FESEM/EDS）、電子微探分析儀 （EPMA）、穿透式電子顯微鏡能量分散能譜儀（TEM/EDS）等分析鈦金屬與陶 瓷間反應介面之微觀結構，並探討CaO 含量對CaO/ZrO2 系陶瓷材料與熔融Ti 介面反應的影響。

Titanium is usually melted in a water-cooled copper crucible by the consumable electrode vacuum arc melting (VAR) instead of vacuum induction melting (VIM) because the ceramic crucible, used in the VIM process, seriously reacts with titanium melt. In addition, the surfaces of titanium castings are chemically milled in order to remove the reaction products between Ti castings and ceramic molds. Therefore, how to control the interfacial reactions between titanium and ceramics is of great concern. The interfacial reactions between Ti and ZrO2 have been subjected to intensive studies in the last few years. Furthermore, the effect of yttria was conducted on the interfacial reactions between Ti and hot pressed Y2O3/ZrO2 mixtures. Our previous important results were published in the Journal of the American Ceramic Society. In this study, the powder mixtures of CaO/ZrO2 will be hot pressed and then allowed to react with titanium melt at 1700°C for 10 min in argon. Various reaction layers at the interface between titanium melt and CaO/ZrO2 samples will be characterized using a scanning electron microscope, an electron probe microanalyzer, and a transmission electron microscope. After the effect of CaO on the interfacial reactions between Ti melt and CaO/ZrO2 samples is fully explored, the ratio of CaO/ZrO2 can be optimized to achieve a better control over the interfacial reactions.