【摘要】：液體潤滑劑在高溫下容易失效,潤滑涂層壽命有限,而固體自潤滑復(fù)合材料不僅在極端工況下具有優(yōu)秀的摩擦學(xué)性能,而且由于自我修復(fù)能力擁有較長的使用壽命,成為摩擦學(xué)的一個(gè)熱門研究領(lǐng)域。由于單一的潤滑劑很難在較寬的溫度范圍內(nèi)實(shí)現(xiàn)潤滑效果,因此對兩種或兩種以上潤滑劑協(xié)同潤滑的研究十分必要。本論文首次以TiAl合金為基體,通過添加復(fù)合潤滑組元Ag、Ti3SiC2和BaF2/CaF2共晶體(ATBC)制備出新型的TiAl基自潤滑材料。含復(fù)合潤滑組元ATBC的Ti Al基自潤滑材料在室溫(RT)-600°C的摩擦磨損性能被研究。研究結(jié)果表明由于Ag、Ti3SiC2和BaF2/CaF2共晶體的協(xié)同潤滑作用,該TiAl基自潤滑材料在所有測試溫度范圍內(nèi)都具有優(yōu)秀的摩擦學(xué)性能。以前的研究中,通常通過在基體中添加固體潤滑劑來制備自潤滑復(fù)合材料。當(dāng)潤滑劑含量較低時(shí),復(fù)合材料摩擦學(xué)性能的改善不明顯,當(dāng)潤滑劑含量較高時(shí),復(fù)合材料的力學(xué)性能會(huì)明顯降低。在基體中添加有效的增強(qiáng)相,將會(huì)是提高復(fù)合材料的強(qiáng)度和耐磨性能的一種有效方法。本論文選擇TiB2來提高TiAl-12Ag自潤滑復(fù)合材料的強(qiáng)度。研究了含潤滑劑Ag和增強(qiáng)相TiB2的TiAl基自潤滑材料在RT到600°C的摩擦磨損性能。結(jié)果顯示復(fù)合材料的耐磨性得到了明顯的提高。TiAl-12Ag-5TiB2復(fù)合材料在不同工況條件(載荷、滑動(dòng)速度和不同摩擦副材料)下的摩擦學(xué)性能被研究。復(fù)合材料的摩擦學(xué)性能依賴于工況條件,在一定載荷范圍內(nèi),摩擦系數(shù)隨著載荷的增加而降低,磨損率隨著載荷的增加而增大;在一定滑動(dòng)速度范圍內(nèi),摩擦系數(shù)和磨損率隨著滑動(dòng)速度的升高而降低;相對于Al2O3和WC-6Co,以Si3N4為摩擦副時(shí),TiAl-12Ag-5TiB2自潤滑復(fù)合材料表現(xiàn)出了最優(yōu)良的摩擦磨損性能。自潤滑復(fù)合材料優(yōu)秀的摩擦學(xué)性能歸因于磨痕表面理想的摩擦層的形成。本文研究了TiAl-12Ag-5TiB2復(fù)合材料摩擦層形成和作用機(jī)理。當(dāng)載荷為12N時(shí),由潤滑膜、機(jī)械混合層和塑性變形層組成的摩擦層形成。塑性變形層加強(qiáng)了材料抵抗變形的能力,與其它層之間的結(jié)合強(qiáng)度高;機(jī)械混合層主要由潤滑相組成,為磨痕表面潤滑膜的鋪展提供物質(zhì)支持,而連續(xù)完整的潤滑膜具有低剪切強(qiáng)度,能夠發(fā)揮良好的潤滑效果,從而有效地降低材料的摩擦系數(shù)和磨損率。
[Abstract]:Liquid lubricant is easy to fail at high temperature, and the life of lubricating coating is limited. Solid self-lubricating composite not only has excellent tribological properties under extreme conditions, but also has long service life due to self-repairing ability. It has become a hot research field in tribology. Because a single lubricant is difficult to achieve lubricating effect in a wide range of temperatures, it is necessary to study the synergistic lubrication of two or more lubricants. In this paper, a new self-lubricating material based on TiAl was prepared by adding Ag,Ti3SiC2 and BaF2/CaF2 eutectic (ATBC) as the base of TiAl alloy for the first time. The friction and wear properties of Ti Al based self-lubricating materials containing composite lubricating component ATBC at room temperature (RT) -600 擄C were investigated. The results show that the self-lubricating material based on Ag,Ti3SiC2 and BaF2/CaF2 has excellent tribological properties in all test temperatures due to the synergistic lubrication effect between TiAl and BaF2/CaF2 eutectic. In previous studies, self-lubricating composites were usually prepared by adding solid lubricants to the matrix. When the lubricant content is low, the tribological properties of the composites are not improved obviously, but the mechanical properties of the composites decrease obviously when the lubricant content is higher. Adding effective reinforcing phase to the matrix will be an effective method to improve the strength and wear resistance of the composites. In this paper, TiB2 is chosen to improve the strength of TiAl-12Ag self-lubricating composites. The friction and wear properties of TiAl based self-lubricating materials containing lubricant Ag and reinforced phase TiB2 at RT to 600 擄C were studied. The results show that the wear resistance of the composites has been obviously improved. The tribological properties of the composites under different working conditions (load, sliding speed and different friction pairs) have been studied. The tribological properties of the composites depend on the working conditions. In a certain range of loads, the friction coefficient decreases with the increase of the load, and the wear rate increases with the increase of the load. The friction coefficient and wear rate decrease with the increase of sliding speed, and the friction and wear properties of TiAl-12Ag-5TiB2 self-lubricating composite show the best performance compared with that of Al2O3 and WC-6Co, when Si3N4 is used as friction pair. The excellent tribological properties of self-lubricating composites are attributed to the formation of an ideal friction layer on the wear-mark surface. In this paper, the formation and mechanism of friction layer of TiAl-12Ag-5TiB2 composites are studied. When load is 12 N, friction layer is formed by lubricating film, mechanical mixing layer and plastic deformation layer. The plastic deformation layer strengthens the ability of material to resist deformation and has high bonding strength with other layers. The mechanical mixing layer is mainly composed of lubricating phase, which provides material support for the spreading of lubricating film on the wear mark surface. The continuous and complete lubrication film has low shear strength and can play a good lubricating effect, thus effectively reducing the friction coefficient and wear rate of the material.
【學(xué)位授予單位】：武漢理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TB333

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