(中南大學(xué) 粉末冶金國(guó)家重點(diǎn)實(shí)驗(yàn)室，長(zhǎng)沙 410083)
摘 要: 在分析和計(jì)算機(jī)準(zhǔn)三維(2.5D)針刺整體炭氈、低密度炭氈孔隙結(jié)構(gòu)的基礎(chǔ)上，研究不同溫度和壓力下反應(yīng)氣體在上述預(yù)制體孔隙中的擴(kuò)散行為、TaC的沉積速率及滲透深度。結(jié)果表明：在800~1000 ℃和60~400 Pa時(shí)，TaCl5氣體在低密度炭氈中的有效擴(kuò)散系數(shù)大于其在準(zhǔn)三維針刺氈中的有效擴(kuò)散系數(shù)。在800~950 ℃時(shí)，TaC在準(zhǔn)三維針刺整體炭氈中的沉積速率大于其在低密度炭氈的沉積速率，但在950~1 000 ℃ 則剛好相反；在800 ℃和不同壓力下，TaC在準(zhǔn)三維針刺整體炭氈中的沉積速率均大于其在低密度炭氈中的沉積速率；TaC在低密度炭氈的沉積過(guò)程受表面反應(yīng)控制和孔隙擴(kuò)散控制的轉(zhuǎn)變溫度為950 ℃，而在準(zhǔn)三維針刺整體氈中的轉(zhuǎn)變溫度則為900 ℃。在800 ℃和200 Pa時(shí)，TaC在不同預(yù)制體中的滲透深度均為100%，隨著沉積溫度的升高以及壓力的升高(400 Pa)和降低(60 Pa)，TaC在準(zhǔn)三維針刺炭氈中的滲透深度顯著降低，且明顯小于同條件下其在低密度炭氈中的滲透深度。
關(guān)鍵字: TaC；化學(xué)氣相滲透；孔隙結(jié)構(gòu)；擴(kuò)散；滲透深度
chemical vapor infiltration of TaC
（State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China）
Abstract:The effects of deposition temperature and pressure on the diffusion behavior of TaCl5 vapor in the perform pores, and the deposition rats, infiltration depths of TaC in the performs were researched on the basis of theoretical analyses of the pore structures of 2.5D needle-punctured felts, low-density carbon felts. The results show that at 800−1 000 ℃ and 60−400 Pa, the effective diffusion coefficient of TaCl5 vapor in low-density felt is larger than that in 2.5D needle-punctured felt; at 800−950 ℃, the deposition rate of TaC in 2.5D needle-punctured perform is larger than that in the low-density perform, but it is opposite at 950−1 000 ℃. At 800 ℃ and 60−400 Pa, the deposition rate of TaC in 2.5D needle-punctured felt is larger than that in low-density felt. The change temperatures controlled by surface reactive kinetics and diffusion kinetics of pore in TaC-CVI process are 950 ℃ in low-density felts and 900 ℃ in 2.5D needle-punctured felts, respectively; at 800 ℃ and 200 Pa, the infiltration depths of TaC in 2.5D needle-punctured felts and low-density felts are all 100%, but decrease obviously with increasing temperature and variation of pressure. In addition, the infiltration depth of TaC in 2.5D needle-punctured felts is less than that in low-density felts.
Key words: TaC; chemical vapor infiltration; pore structure; diffusion; infiltration depth
