本文關(guān)鍵詞： 熱障涂層 微觀納米力學(xué)性能 界面微結(jié)構(gòu)演變 失效機(jī)理 透射電子顯微術(shù)　出處：《中國科學(xué)技術(shù)大學(xué)》2016年博士論文　論文類型：學(xué)位論文

【摘要】：采用低壓/大氣等離子噴涂(LPPS/APS)、電子束物理氣相沉積(EB-PVD)和多弧離子鍍(AIP)方法在鎳基單晶高溫合金表面制備了NiCrA1Y、NiCoCrAlY、 NiCrAlYSiB三種MCrA1Y涂層和8wt.%氧化釔部分穩(wěn)定氧化鋯(8YSZ)+NiCrA1Y、8YSZ+NiCoCrAlY/20wt.%氧化鎂穩(wěn)定氧化鋯(20MSZ)-NiCrAlY三種熱障涂層(Thermal Barrier Coatings, TBCs)。借助納米壓痕測試技術(shù),研究了涂層微觀力學(xué)性能隨氧化溫度變化規(guī)律。以透射電子顯微術(shù)(TEM)為主要研究方法,結(jié)合X-射線衍射(XRD)、掃描電子顯微術(shù)(SEM)和電子能量散射譜(EDS)等分析手段,研究了1100℃氧化過程中涂層界面微結(jié)構(gòu)演化規(guī)律及其涂層失效機(jī)制。在NiCrA1Y涂層中加入Co元素,可提高沉積態(tài)涂層的硬度并降低其彈性模量,在氧化初期,可同時(shí)提高涂層的彈性模量和硬度及其穩(wěn)定性；加入Si和B元素,可降低沉積態(tài)涂層的彈性模量和硬度,但在氧化過程中可穩(wěn)定涂層的彈性模量和提高涂層的硬度。在沉積狀態(tài),因?yàn)槲锵嘟M成、涂層密度和穩(wěn)定性的不同,20MSZ熱障涂層的平均彈性模量和平均硬度都比APS 8YSZ熱障涂層的值��；由于存在擇優(yōu)取向織構(gòu)和多孔隙,沉積態(tài)EB-PVD 8YSZ涂層的彈性模量和硬度都比APS 8YSZ的值小,但是隨著在氧化初期被燒結(jié),其彈性模量和硬度都得到了提高,比APS 8YSZ涂層的值大。由于涂層與基體間存在元素互擴(kuò)散和選擇性內(nèi)氧化,導(dǎo)致NiCrAlY涂層經(jīng)過1100℃恒溫氧化后,涂層與基體之間首先生成了兩層主要由Cr2O3和α-Al2O3組成的致密熱生長氧化物(TGO),Cr2O3層靠近涂層分布,α-Al2O3層靠近基體分布。隨著氧化時(shí)間延長,因?yàn)棣?-Ni3Al的分解,基體內(nèi)靠近界面區(qū)域析出了γ-Al。隨著內(nèi)氮化和內(nèi)氧化的持續(xù),基體內(nèi)靠近界面區(qū)域進(jìn)一步生成hcp-AIN和fcc-TiN,期間由于競爭關(guān)系,hcp-AIN發(fā)生置換反應(yīng)生成α-Al2O3。隨著恒溫氧化的繼續(xù),TGO層不斷增厚且成分中增加了Ni(Al,Cr)2O4、NiO和Y3Al5O12,最終,巨大的熱應(yīng)力集中使涂層在歷經(jīng)1000小時(shí)氧化后沿著界面剝離而失效。1 100℃恒溫氧化初期,APS 8YSZ+LPPS NiCrA1Y熱障涂層的陶瓷層與粘結(jié)層、粘結(jié)層與基體之間先后生長了分層的TGO膜,對(duì)于前者而言,粘附陶瓷層的TGO薄層由α-Al2O3、Cr2O3、NiO和Ni(Al,Cr)2O4混合組成,靠近粘結(jié)層的TGO薄層主要由致密的α-Al2O3和/或Cr2O3組成；對(duì)于后者而言,緊挨粘結(jié)層的TGO薄層由α-Al2O3、Cr2O3和Ni(Al,Cr)2O4混合組成,而貼近基體的TGO薄層主要由致密的α-Al2O3和/或Cr2O3組成。因?yàn)榛w的強(qiáng)化相γ'分解,而氧分壓過低不能氧化分解產(chǎn)物[Al]和[Ti],使得γ-Al和β-Ti在基體內(nèi)靠近界面區(qū)域析出。隨著氧化時(shí)間延長,粘結(jié)層中的富鋁相Al2Y和β-NiAl逐漸消失,涂層逐漸退化,加上TGO層的不斷增厚、孔隙率提高、成分復(fù)雜化以及陶瓷層的相變等因素,導(dǎo)致界面區(qū)域產(chǎn)生熱應(yīng)力集中并進(jìn)而產(chǎn)生微裂紋,由微裂紋的深入擴(kuò)展和連接,致使粘結(jié)層與基體間TGO產(chǎn)生大裂縫,導(dǎo)致熱障涂層于3000小時(shí)氧化后最終整體失效。MCrA1Y涂層和熱障涂層的1100℃C恒溫氧化動(dòng)力學(xué)曲線都基本遵循拋物線氧化規(guī)律。氧化初期MCrA1Y涂層的平均拋物線氧化常數(shù)Kp值約為2.3×10-11g2cm-4s-1,熱障涂層的Kp約為1.8×10-11g2cm-4s-1；穩(wěn)定氧化階段MCrA1Y涂層的約為6.5×10-12g2cm-4s-1,熱障涂層的平均Kp值約為3.5×10-12g2cm-4s-1。涂層的氧化過程遵循氧的吸附、傳質(zhì)和持續(xù)補(bǔ)給并使涂層系統(tǒng)發(fā)生選擇性內(nèi)氧化的擴(kuò)散控制機(jī)制。涂層的退化即親氧性金屬元素Al和Cr儲(chǔ)量逐漸被消耗的過程。而涂層的恒溫氧化失效表現(xiàn)為TGO層逐漸生長進(jìn)而導(dǎo)致界面裂紋的形成、擴(kuò)展和涂層剝離過程。
[Abstract]:The low pressure / air plasma spraying (LPPS/APS), electron beam physical vapor deposition (EB-PVD) and multi arc ion plating (AIP) method to prepare NiCrA1Y in nickel base single crystal superalloy surface NiCoCrAlY, NiCrAlYSiB three MCrA1Y coatings and 8wt.% yttria partially stabilized zirconia (8YSZ) +NiCrA1Y, 8YSZ+NiCoCrAlY/20wt.% Magnesium Oxide stable oxidation zirconium (20MSZ) -NiCrAlY three (Thermal Barrier Coatings, thermal barrier coating TBCs). Using nanoindentation technique, changes with the oxidation temperature of coating micro mechanical properties are studied. By transmission electron microscopic surgery (TEM) as the main research methods, combined with X- ray diffraction (XRD), scanning electron microscopy (SEM) and electron energy dispersive spectroscopy (EDS) analysis method of 1100 DEG C during the oxidation process of coating interface microstructure evolution and coating failure mechanism. Adding Co element in NiCrA1Y coating, can improve the deposited coating The hardness and the elastic modulus decreased, at the initial stage of oxidation, which can improve the coating hardness and elastic modulus and stability; adding Si and B elements, the hardness and elastic modulus can reduce the deposited coating, but the elastic modulus can be stable coating in the oxidation process and improve the hardness of the coating. In the deposition state, because the phase composition, coating density and stability, the average elastic modulus of 20MSZ coatings and the average hardness of APS 8YSZ thermal barrier coating is small; because of the existence of preferential orientation and multi pore, deposited EB-PVD 8YSZ coating elastic modulus and hardness than the APS 8YSZ value is small, but with sintering in oxidation initially, the elastic modulus and hardness are improved, than the APS values of 8YSZ coating. Because of the existence of element diffusion and selective oxidation of the coating and the substrate, resulting in NiCrAlY coating after isothermal 1100 oxygen After that, the coating and the substrate is first generated dense hot two layer is mainly composed of Cr2O3 and alpha -Al2O3 composed of growth (TGO), Cr2O3 oxide coating layer close to the distribution, a -Al2O3 layer near the substrate distribution. With oxidation time, because the decomposition of gamma'-Ni3Al, the matrix near the interface region of -Al. with continuous precipitation of gamma nitride and internal oxidation and further formation of hcp-AIN and fcc-TiN matrix near the interface region during the competition, hcp-AIN was replaced with -Al2O3. to generate alpha oxidation, increased Ni and TGO layer thickening components (Al, Cr) 2O4, NiO and Y3Al5O12, finally, great thermal stress concentration the coating after 1000 hours after oxidation along the interfacial debonding failure.1 100 constant temperature oxidation stage, the ceramic layer APS 8YSZ+LPPS NiCrA1Y thermal barrier coating and adhesive layer, adhesive layer and the substrate between the first layer of T growth For the former, GO film, TGO layer adhesion of ceramic coatings by alpha -Al2O3, Cr2O3, NiO and Ni (Al, Cr) 2O4 mixture, TGO thin layer near the bonding layer is mainly composed of a dense -Al2O3 and / or Cr2O3; for the latter, next to the TGO thin adhesive layer by a -Al2O3. Cr2O3 and Ni (Al, Cr) 2O4 mixture, TGO thin and close to the substrate is mainly composed of a -Al2O3 compact and / or Cr2O3. Because the matrix strengthening phase of R 'decomposition, and the oxygen pressure too low oxidation decomposition products of [Al] and [Ti], the -Al gamma and beta -Ti in the matrix near the interface. Area. With the oxidation time, rich aluminum bonding layer in phase Al2Y and beta -NiAl gradually disappear, coating gradually degraded, and the TGO layer increased, the porosity increased, and the complex composition of the ceramic layer of phase change and other factors, resulting in the interface region produces thermal stress concentration and micro cracks, by micro cracks the Further expansion and connection, the bonding between the coating and the substrate TGO to produce large cracks, 1100 DEG C isothermal oxidation kinetic curves lead to thermal barrier coating in 3000 hours after the final overall oxidation failure of.MCrA1Y coating and thermal barrier coating are basically follow the parabolic oxidation law. Initial average oxidation parabolic oxidation constant Kp MCrA1Y coated layer is about 2.3 * 10-11g2cm-4s-1 Kp, thermal barrier coating is about 1.8 * 10-11g2cm-4s-1; stable oxidation of MCrA1Y coating is about 6.5 * 10-12g2cm-4s-1, the average value is about Kp thermal barrier coating adsorption and oxidation process of 3.5 * 10-12g2cm-4s-1. coatings follow oxygen, mass transfer and continuous supply and selective diffusion coating system of internal oxidation process of the coating degradation control mechanism. The oxophilic metals Al and Cr reserves gradually by consumption. And the isothermal oxidation coating failure for TGO layer gradually, which led to the growth of the interface The formation, expansion of the crack and the stripping process of the coating.

【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TG174.4
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本文編號(hào)：1481459