本文關鍵詞：熱障涂層高溫CMAS腐蝕應變場的DIC表征與分析　出處：《湘潭大學》2016年碩士論文　論文類型：學位論文

  更多相關文章： DIC法 熔融CMAS腐蝕 熱障涂層 應變場

【摘要】：熱障涂層(TBCs)作為一種關鍵的隔熱防護材料被應用在航空渦輪發(fā)動機上,顯著降低了合金表面溫度,促進了航空事業(yè)的進一步發(fā)展。然而在航空發(fā)動機高推重比的發(fā)展趨勢下,燃氣進口溫度的要求不斷提高,熱障涂層CMAS腐蝕成為服役環(huán)境中最危險的失效形式。如何獲得熱障涂層CMAS腐蝕失效機制的充分理解是今后航空發(fā)動機取得任何進展的關鍵,而應變場的表征可以為CMAS腐蝕機制的理解提供直接的實驗依據(jù)。由于熱障涂層CMAS腐蝕時應變場的表征是在1200°C以上的高溫下進行的,傳統(tǒng)的測應變方法不再適用。因此本文采用了一種光學非接觸式測應變方法,數(shù)字圖像相關法(DIC)來表征CMAS高溫腐蝕熱障涂層的應變場,為日后涂層本構關系的建立提供一個數(shù)量級的指導。主要研究內(nèi)容如下:1、利用高壓噴槍將特定比例的耐高溫無機膠與氧化亞鈷的混合物在熱障涂層樣品截面制作耐高溫人工散斑;實驗室人工配制與實際火山灰相似成分的CMAS粉末,用研缽不斷研磨使得CMAS粉末的粒徑分布集中在20μm左右,并用毛筆刷將一定量CMAS粉均勻涂覆在熱障涂層樣品的表面;將制好隨機散斑且涂有CMAS粉末的樣品放入DIC設備裝置中的恒溫電阻爐中,在1250°C下煅燒30 min進行CMAS高溫腐蝕熱障涂層的實驗,隨爐冷卻;DIC實時監(jiān)測采集冷卻過程中樣品截面的數(shù)字圖像,利用ARAMIS計算分析軟件進行后處理,最終得到CMAS腐蝕熱障涂層在冷卻過程中應變場的演變。2、研究了熱障涂層在從1250°C冷卻到25°C過程中,有、無CMAS腐蝕時應變場的演變過程。發(fā)現(xiàn)涂層在不同CMAS涂覆量腐蝕下,冷卻到300-400°C時,陶瓷層與基底的界面處出現(xiàn)了明顯的拉應變,涂層開始開裂,臨界開裂應變約為-0.7%;無CMAS腐蝕時,冷卻到100°C時陶瓷層與基底的界面處開始開裂,臨界應變約為-1.6%;當溫度降到25°C時,所有樣品均已剝落失效。除此之外,研究發(fā)現(xiàn)在冷卻過程中,CMAS腐蝕不帶基底的陶瓷層時應變大小約為-0.5%。3、建立了CMAS高溫腐蝕熱障涂層應力應變場的理論模型,分析得到應力應變解析解。代入適當?shù)牟牧蠀?shù),計算得到從1250°C冷卻到25°C過程中,不同溫度下的應力應變值,發(fā)現(xiàn)在冷卻過程中,應力應變理論值均隨溫度降的增大在不斷增大,無CMAS腐蝕時應力值最大達到了-200MPa,應變最大為-1.7%,有CMAS腐蝕時應力值最大達到了-900MPa,應變最大為-1.5%。并將應變理論計算值與實驗結果相對比,最終發(fā)現(xiàn)二者變化趨勢一致,基本吻合。
[Abstract]:Thermal barrier coating (TBCs), as a key thermal insulation protection material, has been used in aero-turbine engine to reduce the surface temperature of the alloy. It has promoted the further development of aeronautical industry. However, under the development trend of high propulsion and weight ratio of aero-engine, the requirement of gas inlet temperature has been raised continuously. Thermal barrier coating (CMAS) corrosion has become the most dangerous failure form in service environment. How to get a full understanding of the mechanism of thermal barrier coating CMAS corrosion failure is the key to any progress of aero-engine in the future. The characterization of the strain field can provide a direct experimental basis for the understanding of the corrosion mechanism of CMAS. Since the characterization of the strain field of the thermal barrier coating CMAS corrosion is carried out at a high temperature above 1200 擄C. The traditional strain measurement method is no longer applicable, so an optical non-contact strain measurement method, digital image correlation method (CMAS), is used to characterize the strain field of CMAS thermal barrier coatings. It provides an order of magnitude guidance for the establishment of the constitutive relationship of coatings in the future. The main research contents are as follows: 1. The mixture of high temperature resistant inorganic adhesive and cobalt oxide was prepared by high pressure spray gun on the cross section of thermal barrier coating sample. The CMAS powder with similar composition to the actual pozzolanic ash was artificially prepared in laboratory, and the particle size distribution of CMAS powder was concentrated at about 20 渭 m by continuous grinding with a mortar. A certain amount of CMAS powder is evenly coated on the surface of the thermal barrier coating sample with brush brush. A sample of random speckle and coated with CMAS powder is placed in a constant temperature resistance furnace in a DIC device. The CMAS high temperature corrosion thermal barrier coating was calcined at 1250 擄C for 30 min and cooled with furnace. The digital image of the sample section during cooling process was monitored by DIC and the post-processing was carried out by using the software of ARAMIS calculation and analysis. Finally, the evolution of strain field in the cooling process of CMAS corrosion thermal barrier coating was obtained. It was studied that the thermal barrier coating was cooled from 1250 擄C to 25 擄C. It is found that when the coating is cooled to 300-400 擄C under different amount of CMAS coating corrosion, the obvious tensile strain appears at the interface between the ceramic coating and the substrate. The critical cracking strain is about -0.7. In the absence of CMAS corrosion, the interface between the ceramic layer and the substrate begins to crack at 100 擄C, and the critical strain is about -1.6; When the temperature drops to 25 擄C, all the samples have spalling and failure. In addition, it is found that the strain of CMAs is about -0.5.3 when the ceramic layer without substrate is corroded during the cooling process. The theoretical model of stress-strain field of CMAS high temperature corrosion thermal barrier coating is established, and the analytical solution of stress and strain is obtained by analyzing. The process of cooling from 1250 擄C to 25 擄C is calculated by adding appropriate material parameters. The stress-strain values at different temperatures show that the theoretical values of stress-strain increase with the increase of temperature drop in the cooling process, and the maximum stress value reaches -200MPa in the absence of CMAS corrosion. The maximum strain is -1.7, the maximum stress value is -900MPa when there is CMAS corrosion, and the strain maximum is -1.5. The calculated strain theory is compared with the experimental results. Finally, it is found that the change trend of the two is consistent and basically consistent.
【學位授予單位】：湘潭大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TG174.4
，

本文編號：1427358