本文選題：熱浸鋁 + 微弧氧化��； 參考：《沈陽理工大學》2017年碩士論文

【摘要】：TC4鈦合金具有比強度高、加工技術成熟等優(yōu)點,得到廣泛的應用。但由于摩擦系數(shù)大、工作溫度低限制了其應用范圍。表面處理可以在保持TC4鈦合金基體力學性能的同時,改善材料的表面性能。本文采用熱浸鋁和微弧氧化復合處理的方法在TC4合金表面制備復合涂層,并對涂層的氧化性能進行研究。TC4鈦合金在750℃熔融鋁液中浸鍍3min后,表面形成一層純鋁鍍層,800℃擴散退火3h后,純鋁層消失,轉(zhuǎn)變?yōu)橛蒚i Al_3相組成的有許多孔洞的擴散層。微弧氧化后在Ti Al_3擴散層表面形成了一層Al_2Ti O_5陶瓷層。電解液中Na Al O_2含量越高,膜層厚度越大,超過4g/L后,表面質(zhì)量變差。提高占空比和正向電壓都有利于陶瓷層的生長。TC4基體和熱浸鋁試樣在850℃和900℃進行循環(huán)氧化實驗表明,熱浸鋁顯著提高了鈦合金的高溫氧化性。熱浸鋁試樣的氧化動力學曲線呈拋物線形。850℃高溫氧化過程中,表面形成了一層致密的Al_2O_3保護層,在900℃高溫氧化后,表面出現(xiàn)了由Al_2O_3和Ti O_2組成的較厚的混合氧化層。分別對在電解液1(Na_2Si O_(3 )8g/L、KOH 2g/L、Na Al O_2 4g/L)和電解液2(Na_2Si O_(3 )8g/L、KOH 2g/L)中復合處理的試樣在850℃、900℃和950℃進行循環(huán)氧化實驗,分析溶液成分對涂層高溫氧化性的影響。實驗結果表明,復合處理試樣在850℃高溫氧化性能優(yōu)于熱浸鋁試樣。900℃溫度下,由于Al_2Ti O_5陶瓷層和Ti Al_3擴散層熱膨脹系數(shù)不同,導致陶瓷層出現(xiàn)裂紋。氧化進行至一定程度后,陶瓷層脫落。950℃溫度下,在溶液2中制備的試樣陶瓷層更早脫落。對在電解液1中制備的試樣在1000℃進行循環(huán)氧化實驗,Al_2Ti O_5氧化分解為Al_2O_3和Ti O_2,彌合了陶瓷層產(chǎn)生的一部分裂紋,減緩了陶瓷層的脫落。氧化過程中伴隨著Al元素的擴散現(xiàn)象,擴散層與基體之間出現(xiàn)了新的擴散層,擴散層中Ti Al_3相一部分轉(zhuǎn)變?yōu)門i Al_2,溫度越高,此現(xiàn)象越明顯。
[Abstract]:TC4 titanium alloy has many advantages, such as high specific strength and mature processing technology. However, because of the large friction coefficient and low working temperature, the application range of the titanium alloy is limited. The surface treatment can improve the surface properties of the TC4 titanium alloy and improve the surface properties of the materials. This paper adopts the method of compound treatment of Hot Dipping Aluminum and micro arc oxidation. A composite coating was prepared on the surface of TC4 alloy, and the oxidation properties of the coating were studied. After.TC4 titanium alloy was dipped in 750 C molten aluminum, a layer of pure aluminum coating was formed on the surface. After 800 C diffusion annealing for 3h, the pure aluminum layer disappeared and turned into a diffusion layer of many holes composed of Ti Al_3 phase. After micro arc oxidation, the surface of the diffusion layer on Ti Al_3 was on the surface of Ti Al_3. A layer of Al_2Ti O_5 ceramic layer is formed. The higher the content of Na Al O_2 in the electrolyte, the greater the thickness of the film, the higher the thickness of the film, the worse the surface quality. The increase of the duty ratio and the positive voltage are beneficial to the growth of the ceramic layer and the cyclic oxidation of the.TC4 matrix and the hot dipped aluminum sample at 850 and 900 C, indicating that the hot dipping aluminum greatly improves the high titanium alloy. The oxidation kinetic curve of the hot dipped aluminum specimen shows a dense Al_2O_3 protective layer during the high temperature oxidation process of parabolic.850 C. After oxidation at 900 C, the surface has a thicker mixed oxidation layer composed of Al_2O_3 and Ti O_2, respectively, to the electrolyte 1 (Na_2Si O_ (3) 8g/L, KOH 2g/L, Na Al) L) and the samples of the electrolyte 2 (Na_2Si O_ (3) 8g/L, KOH 2g/L) were treated by cyclic oxidation at 850, 900 and 950. The effect of the composition of the solution on the high temperature oxidation of the coating was analyzed. The experimental results showed that the high temperature oxidation performance of the composite treated samples was better than that of the hot dipped aluminum at the temperature of the hot dipped aluminum at 850 C, due to the Al_2Ti O_5 ceramic layer and the Al_2Ti O_5 ceramic layer. The thermal expansion coefficient of Ti Al_3 diffusion layer is different, which leads to the crack in the ceramic layer. After oxidation to a certain degree, the ceramic layer prepared in solution 2 at the temperature of.950 centigrade of the ceramic layer falls off earlier. The sample prepared in the electrolyte 1 is cyclic oxidation at 1000 C, and Al_2Ti O_5 is oxidized to Al_2O_3 and Ti O_2. A part of the crack produced in the ceramic layer slows down the falling of the ceramic layer. With the diffusion of Al elements in the oxidation process, a new diffusion layer appears between the diffusion layer and the matrix, and the Ti Al_3 phase in the diffusion layer is converted to Ti Al_2. The higher the temperature, the more obvious the phenomenon is.

【學位授予單位】：沈陽理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG174.4

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