等离子喷涂纳米热障涂层热震性能

采用等离子喷涂工艺制备常规和纳米结构ZrO2-7%Y2O3热障涂层,比较两种涂层在850℃下的热震性能,并探讨其热震失效机理。结果表明,不管是首次出现宏观裂纹(局部剥落)还是达到热震失效,纳米结构热障涂层的热震次数都明显高于相应的常规涂层。相对于常规涂层,纳米结构涂层有较好的抗热震性能。等离子喷涂常规热障涂层的热震失效形式为大面积整体剥落,而纳米结构热障涂层热震失效形式为边角局部剥落。     

等离子喷涂梯度热障涂层的抗热震性能

对比研究了等离子喷涂梯度热障涂层与双层热障涂层,试验中梯度热障涂层选用不同比例的NiCoCrAlY与ZrO₂-8%Y₂O₃复合粉末作为梯度过渡层材料,并对两种结构的热障涂层进行了抗热震性能试验。抗热震试验结果表明,梯度热障涂层的抗热震寿命明显高于双层热障涂层的抗热震寿命。     

等离子喷涂ZrO2热障涂层热冲击破坏研究

对比研究了等离子喷涂ZrO2梯度热障涂层及传统的双层结构热障涂层,选择NiCoCrAlTaY合金粉末作为热障涂层的粘结底层材料、7％Y2O3-ZrO2作为热障涂层的面层材料、不同比例的NiCoCrAlTaY与7％Y2O3-ZrO2(YPZ)复合粉末作为梯度过渡层材料,然后进行热冲击试验、金相分析及扫描电子显微镜形貌分析,结果表明梯度热障涂层热冲击寿命明显高于传统的双层结构热障涂层。     

等离子喷涂层的热震性能

对不同成分的等离子涂层粘结层进行了热震性能试验。通过观察和探讨其破坏情况,对涂层与基体的结合机理及影响结合强度的因素做了深入分析。为进一步改善涂层性能,提高工艺有了可靠依据。     

CeO2添加剂对等离子喷涂ZrO2涂层抗热震性的影响

采用SEM,EPMA和热震方法,研究了CeO2添加剂对等离子喷涂ZrO2i涂层抗热震性能的影响。结果表明：当CeO2由0增加到9.0%（质量分数,下同）时,涂层的抗热震起裂次数和失效次数分别由32次和46次增加到76次和105次;继续增加CeO2,涂层的抗热震性能急剧下降。ZrO2 9.0?O2涂层在热循环中形成的网状微裂纹,不仅可降低涂层中的应力,也可提高涂层开裂的临界温差,从而可改善其抗热震性能。     

等离子喷涂Al2O3与ZrO2复合热障涂层的高温性能

采用等离子喷涂(PS)方法，在GH536高温合金基材上制备了传统的双层热障涂层(TBCs)和2种含有Al2O3与ZrO2陶瓷复合层的3层热障涂层。传统TBC8结构为Ni22Cr10AlY合金连接层和8％Y2O3部分稳定的ZrO2(8YPSZ)陶瓷顶层；3层TBCs中分别采用置于8YPSZ陶瓷层内层及外层的Al2O3与8YPSZ复合层。3种类型试样的100h。1050℃静态氧化试验及1050℃热震试验结果表明：3层涂层较双层涂层的氧化阻力提高，双层涂层的热震阻力最佳，氧化阻力最差。不同复合层形式试样的热振失效方式和寿命也有差别，复合层置于陶瓷层外层热震寿命略高，但100h氧化增重有明显提高，抗氧化性降低。     

Al2O3对等离子喷涂热障涂层高温氧化及热震性能的影响

采用等离子喷涂 (PS)在GH5 36高温合金基材上制备了典型的双层热障涂层 (TBCs)和两种分别加入了Al2 O3 陶瓷成分的复合热障涂层。典型的TBCs采用Ni2 2Cr10AlY连接层与 8%Y2 O3 稳定的 (8YPSZ)顶层的双层结构 ;多层涂层分别采用Al2 O3 与Ni2 2Cr10AlY复合的连接层和Al2 O3 与 8YPSZ复合的顶层。3种类型试样的10 0h ,10 0 0℃静态氧化及 10 5 0℃热震试验的结果分析表明 :8YPSZ Al2 O3 的复合氧障层具有最佳的氧化阻力 ;Ni2 2Cr10AlY 8YPSZ双层涂层的热震阻力最佳 ,氧化阻力最差 ;连接层采用Ni2 2Cr10AlY Al2 O3 复合涂层具有热震和静态氧化条件下综合优良的高温热循环性能     

等离子喷涂常规和纳米ZrO2-7％Y2O3热障涂层隔热性能

采用等离子喷涂工艺在TiAl合金表面制备常规和纳米ZrO2-7％Y2O3(质量分数)热障涂层,分析了两种涂层的组织结构,并对其隔热性能进行了比较.结果表明,等离子喷涂常规热障涂层呈典型的层状堆积特征,而纳米涂层为特殊的两相结构.相对于常规涂层,纳米涂层有较好的隔热性能;在1100℃时,等离子喷涂常规及纳米涂层的隔热温度分别为83、127℃.     

等离子喷涂ZrO2—NiCoCrAlY梯度热障涂层的抗热震性及失效机理

研究了ZrO2-NiCoCrAlY热障涂层的抗热震性和热震失效机理。实验结果表明,梯度热隙涂层能明显延缓热震裂纹的形成和扩展,具有较高的抗热震性。热震裂纹形成与扩展主要在粘结层与基体的界面处。随热循环次数的增加,热震裂纹可在表面陶瓷层内和陶瓷层与过渡层的界面处形成。实验表明热障涂层热震失效的过程主要是裂纹形成、扩展及涂层剥落,粘结层的氧化是导致涂层剥落失效的重要原因。     

等离子喷涂ZrO2热障涂层孔隙结构的研究

采用等离子喷涂在铝合金基体表面制备ZrO2-Ni/Al梯度热障涂层.利用定量金相分析技术对ZrO2陶瓷层、陶瓷一中间层过渡区和ZrO2 Ni/Al中间层的孔隙率、孔隙大小和孔隙形态进行了分析.结果表明,各区域的孔隙率、孔隙大小、孔隙形状服从相似的概率分布;陶瓷一中间层过渡区的孔隙率最高(5.97%),ZrO2陶瓷层和ZrO2 Ni/Al中间层的孔隙率略低;涂层中孔隙尺寸为1～10 μm的占72%～80%;孔隙大多呈现等轴状(形状系数Fk＞0.94),其数量约为84%～87%.     

Thermal shock testing of thermal barrier coating/bondcoat systems

Various methods of thermal shock testing are used by aircraft and industrial gas turbine engine (IGT) manufacturers to characterize new thermal barrier coating systems in the development stage as well as for quality control. The cyclic furnace oxidation test (FCT), widely used in aircraft applications, stresses the ceramic/bondcoat interface, predominantly through thermally grown oxide (TGO) growth stress. The jet engine thermal shock (JETS) test, derived from a burner rig test, creates a large thermal gradient across the thermal barrier coating (TBC), as well as thermomechanical stress at the interface. For IGT applications with long high-temperature exposure times, a combination of isothermal preoxidation and thermal shock testing in a fluidized bed reactor may better represent the actual engine conditions while both types of stress are present. A comparative evaluation of FCT, JETS, and a combined isothermal oxidation and fluidized bed thermal shock test has been conducted for selected ceramic/bondcoat systems. The results and the failure mechanisms as they relate to the TBC system are discussed. A recommendation on the test method of choice providing best discrimination between the thermal shock resistance of the ceramic layer, the ceramic/bondcoat interface, and even substrate related effects, is given. This paper was presented at the 2nd International Surface Engineering Congress sponsored by ASM International, on September 15–17, 2003, in Indianapolis, Indiana, and appeared on pp. 520–29.     

ZrO2热障涂层残余应力分析

用扫描电子显微镜(SEM)观察了等离子喷涂ZrO2涂层的显微结构,并用X射线衍射法(XRD)测试了ZrO2涂层相的组成和残余应力.同时测试了激光冲击处理和激光热处理后的ZrO2涂层残余应力分布,分析了热障涂层残余应力形成机理.结果表明,等离子喷涂ZrO2涂层表面残余应力均为拉应力,其均值为179.2MPa,经激光表面处理后的ZrO2涂层残余应力均表现为压应力;热应力对涂层残余应力贡献最大,当热应力超过涂层结合强度时,涂层脱落,通过控制涂层残余应力可以提高涂层界面结合强度.     

Thermal shock testing of burner cans coated with a thick thermal barrier coating

Thick (1.8 mm) thermal barrier coatings were air-plasma-sprayed onto two different substrate geometries, including small circular substrates and burner cans. Two different top-coating spray parameters were used, where the settings of the substrate temperature and the lamella thickness were varied. A segmentation crack network was found in the top coatings sprayed using a high substrate temperature and a high lamella thickness. The density of segmentation cracks was found to be independent of substrate geometry. No segmentation cracks were found in the top-coatings when a low substrate temperature and a low lamella thickness were used. In the segmented burner can, after 1000 thermal shock cycles, the segmentation crack network was still stable and no severe cracks had formed in the top coating. In the nonsegmented burner can, cracks were formed after only 35 thermal shock cycles. Among the crack types, horizontally oriented cracks were found in the top coating close to, and sometimes reaching, the bond coating. Cracks of this type are not tolerated in thermal barrier coatings because they can cause failure of the coating. Regarding the lifetime of the segmented burner can, it is believed the failure will be dependent on other mechanisms, such as bond-coating oxidation or top-coating decomposition.     

预氧化处理对热障涂层热冲击性能及残余应力的影响

采用等离子喷涂工艺在镍基高温合金基体上制备了热障涂层(底层为MCrAlY,面层为ZrO2+ 8％ Y2O3),通过控制高真空烧结炉的氧分压对涂层进行预氧化处理,分析了预氧化处理对热障涂层热冲击性能和涂层应力状态的影响.结果表明,预氧化处理提高了粘接层的致密度,涂层组织变得均质化,降低了粘结层由于凸起尖角产生复杂应力的概率;有效干预热生长氧化物(TGO)的生长过程,降低了TGO的生长速度;热障涂层残余应力随热冲击次数的增加而增大,但经过预氧化处理的涂层应力增长幅度较缓慢,经过400次热冲击后的残余应力为492.5 MPa,未经过预氧化处理涂层热冲击350次后应力值为650.1 MPa.     

等离子喷涂纳米Al_2O_3-TiO_2-SiO_2-SiC涂层抗热震性能

将纳米结构Al2O3、TiO2、SiO2、SiC粉体经液相喷雾造粒的方法,制备出适合等离子喷涂的球形复合粉体,采用等离子喷涂技术制备出含纳米结构的陶瓷涂层.通过水淬法,将涂层试样分别经500、700、900和1 100 ℃加热并保温10 min,然后投入冷水中以测量其抗热震能力,通过宏观和SEM照片加以观察,分析其失效的机理.试验结果表明,该纳米结构涂层在较低温度( ＜700 ℃)具有优良的抗热震性能.     

Penetration treatment of plasma-sprayed ZrO2 coating by liquid Mn alloys

The penetration phenomena of liquid manganese (Mn) alloy into porous ZrO₂ (8 vvt % Y₂O₃) coating plasma sprayed on SS400 steel substrate was studied by heating in a vacuum atmosphere. The improvement in mechanical properties of the coating by heat treatment with liquid Mn alloys was examined. Liquid Mn alloys, such as Mn-Cu, Mn-Sn, and Mn-In, rapidly penetrated the coating and formed a chemical bond between the coating and the substrate. The densification of the ZrO₂ coating occurred when ZrO₂ particles were sintered with liquid Mn alloys that penetrated the porous coating. The dense coating was free of porosity, and its hardness increased after heat treatment with Mn alloys, compared with assprayed ZrO₂ coating. Moreover, the fracture toughness of the coating reached the same levels as those of sintered yttria-stabilized PSZ.     

Thermal and mechanical properties of ZrO2-CeO2 plasma-sprayed coatings

The thermal and mechanical properties of ZrC₂-C_{eO 2}plasma-sprayed coatings were evaluated to examine their potential as a thermal barrier coating. ZrO₂-CeO₂ solid-solution powders containing up to 70 mol % CeO₂ are successfully plasma sprayed, but cerium content decreases during spraying due to the vaporization of cerium oxide. Hardness is greatest at 30 mol% CeO₂. With increased CeO₂ content, the thermal conductivity decreases to 0.5 W/m K and the thermal expansion coefficient increases to 12.5 x 10_-6 /K. Increased torch input power causes both the relative density and the hardness to increase monotonically, while the thermal conductivity and the thermal expansion coefficient are not significantly affected. When heated above 1300 K, the coating shrinks considerably due to sintering and its thermal conductivity increases abruptly.     

Improvement of thermal shock resistance for thermal barrier coating on aluminum alloy with various electroless interlayers

NiCoCrAlY/8YSZ coating was firstly directly deposited on aluminum alloy 5A06 by atmospheric plasma spray to make it applicable to short-time high temperature condition. The failure after thermal shock test was mainly due to the stress caused by thermal expansion mismatch between the bond coat and the substrate as well as the galvanic corrosion of the aluminum alloy. Ni-P, Ni-W-P and Ni-Cu-P as interlayers were electrolessly deposited on the substrate in order to mitigate the thermal stress. The composition and thermal transformation of the interlayers were investigated. Thermal shock resistance and bonding strength of multilayer coatings (interlayer/NiCoCrAlY/8YSZ) were tested. Diffusion layers mainly composed of AlNi, Al₃Ni₂ and Al₃Ni were observed between the interlayers and the substrate after thermal shock test. The oxidation of the substrate was effectively inhibited. Ni-P interlayer obtained at lower pH value was superior to the other two interlayers and enhanced the thermal shock life from 38 to more than 200 cycles. With the application of the Ni-P and Ni-Cu-P interlayers, the bonding strength examined by pull-off test was also largely improved from 11.7 MPa to 18.8 and 19.0 MPa, respectively.     

Comparison of thermal shock behaviors between plasma-sprayed nanostructured and conventional zirconia thermal barrier coatings

NiCoCrAlTaY bond coat was deposited on pure nickel substrate by low pressure plasma spraying(LPPS), and ZrO2-8%Y2O3 (mass fraction) nanostructured and ZrO2-7%Y2O3 (mass fraction) conventional thermal barrier coatings(TBCs) were deposited by air plasma spraying(APS). The thermal shock behaviors of the nanostructured and conventional TBCs were investigated by quenching the coating samples in cold water from 1 150, 1 200 and 1 250 ℃, respectively. Scanning electron microscopy(SEM) was used to examine the microstructures of the samples after thermal shock testing. Energy dispersive analysis of X-ray(EDAX) was used to analyze the interface diffusion behavior of the bond coat elements. X-ray diffractometry(XRD) was used to analyze the constituent phases of the samples. Experimental results indicate that the nanostructured TBC is superior to the conventional TBC in thermal shock performance. Both the nanostructured and conventional TBCs fail along the bond coat/substrate interface. The constituent phase of the as-sprayed conventional TBC is diffusionless-transformed tetragonal(t′). However, the constituent phase of the as-sprayed nanostructured TBC is cubic(c). There is a difference in the crystal size at the spalled surfaces of the nanostructured and conventional TBCs. The constituent phases of the spalled surfaces are mainly composed of Ni2.88Cr1.12 and oxides of bond coat elements.