發(fā)布時間：2018-03-11 14:44

  本文選題：熱障涂層　切入點：高溫氧化　出處：《湘潭大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：熱障涂層以其優(yōu)異的隔熱、耐磨和耐蝕性被廣泛應(yīng)用在航空渦輪發(fā)動機中,然而,熱障涂層的幾何形狀、微觀結(jié)構(gòu)和服役環(huán)境都極其復(fù)雜,使得涂層在無法預(yù)知的情況下開裂,最終導(dǎo)致涂層剝落失效。在服役過程中,熱生長氧化物(thermally grown oxide,TGO)在力、熱、化學(xué)勢多重因素作用下生長,極大地限制了TBCs在航空發(fā)動機上的安全應(yīng)用。本文重點考慮了TGO在力化耦合作用下的生長,并借助有限元軟件進行仿真模擬計算分析,主要研究內(nèi)容和結(jié)果如下:第一,通過建立簡單的高溫氧化模型,研究氧化物厚度的演化規(guī)律,得到了TGO厚度與溫度、氧分壓、表面粗糙度等外部條件的解析表達式。進一步分析了溫度、氧分壓、表面粗糙度等外部環(huán)境條件對氧化層厚度的影響,結(jié)果表明:TGO氧化初期,生長速度很快,隨著時間的增長,反應(yīng)速度逐漸減小,最后趨于平穩(wěn);溫度和表面粗糙度對氧化層厚度的影響較大,而氧分壓對其影響較小;隨著溫度升高和表面粗糙度增加,氧化層的厚度越大并且氧化反應(yīng)程度越高。第二,在小變形假設(shè)情況下,將總應(yīng)變分為彈性應(yīng)變和生長應(yīng)變,通過生長應(yīng)變建立TBCs高溫氧化過程中濃度對力場的影響,建立TGO生長過程中的力場的本構(gòu)關(guān)系;在化學(xué)勢中加入平均應(yīng)力,通過Fick定律建立力對化學(xué)場的影響,得到化學(xué)場的本構(gòu)關(guān)系;在TBCs高溫氧化過程中引入一個變量n來表示TGO的生長過程,當(dāng)其取1表示TGO,取0表示粘結(jié)層,得到TGO的演化方程。結(jié)合力平衡方程、擴散反應(yīng)方程、TGO演化方程以及本構(gòu)方程建立TBCs高溫氧化的力化耦合模型。第三,借助于COMSOL建立TGO生長的有限元模型,給定力場和化學(xué)場的邊界條件及初始條件,將力化耦合理論的控制方程寫成弱形式輸入COMSOL,進而研究TGO生長和涂層內(nèi)應(yīng)力的耦合規(guī)律。結(jié)果表明:波峰處TGO氧化生長速率比波谷大,且TGO厚度隨界面粗糙度的增加而增大;TBCs的界面粗糙度是影響涂層內(nèi)應(yīng)力分布的關(guān)鍵因素,隨著粗糙度的增大,應(yīng)力值在不斷增加;涂層內(nèi)的壓應(yīng)力對TGO生長有抑制作用,拉應(yīng)力有促進作用。
[Abstract]:Thermal barrier coatings with excellent heat insulation, wear resistance and corrosion resistance has been widely used in aviation turbine engine, however, thermal barrier coating geometry, microstructure and service environment are extremely complex, which makes the coating cracking in the unpredictable situation, resulting in coating peeling failure. In the course of service, the thermally grown oxide (thermally grown oxide, TGO) in force, thermal, chemical potential growth under the effect of multiple factors, which greatly limits the security application of TBCs in aircraft engine. This paper focuses on the TGO under the coupling effect of growth in force, and simulation calculation and analysis of finite element software, the main research contents and results are as follows: 1. Through the establishment of high temperature oxidation model, the evolution of oxide thickness, the thickness of TGO and temperature, oxygen partial pressure, the analytical expression of surface roughness and other external conditions further. The analysis of the temperature, oxygen partial pressure, surface roughness and other external environmental conditions on the thickness of the oxide layer. The results showed that the oxidation of TGO at the early stage, growth is very fast, with the increase of time, the reaction rate decreases, finally tends to be stable; temperature and surface roughness of larger influence on the thickness of the oxide layers, and oxygen the pressure has little influence on it; with the increase of temperature and the surface roughness increases, the thickness of the oxide layer is larger and higher oxidation degree. In second, small deformation assumption, the total strain is divided into elastic strain and strain growth, establish the influence of the concentration of TBCs during high temperature oxidation of stress field by growing strain. The constitutive relation of the growth process established in TGO force field; with the average stress in the chemical potential, through the Fick law of influence on the chemical stress field, the constitutive relation of chemical field; the introduction of a high temperature in the process of oxygen in TBCs The variable n to represent the growth process of TGO, when the 1 TGO, 0 said adhesive layer, we obtain the evolution equation of TGO. Combined with the force balance equation, diffusion reaction equation, TGO evolution equation and constitutive equation of force coupling model of high-temperature oxidation of TBCs. Third, with the aid of the finite element in COMSOL building TGO the growth model of the given field and chemical field boundary conditions and initial conditions, the force control equations of the coupling theory in the weak form of input COMSOL, and TGO on the growth and coupling of the internal stress of coating. The results show that the peak of TGO oxidation growth rate than trough, and the thickness of the interfacial roughness of TGO the increase of TBCs; the interface roughness is a key factor affecting the distribution of the internal stress of coating, with the increase of roughness, the stress value increased; compressive stress within the coating could inhibit the growth of TGO, the tensile stress has a role in promoting.

【學(xué)位授予單位】：湘潭大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG174.4

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