激光重熔纳米氧化锆热障涂层的抗热冲击性能

采用纳米氧化锆团聚粉末和等离子喷涂技术制备了纳米氧化锆涂层,试验研究了激光重熔工艺参数(激光比能量)对纳米氧化锆涂层抗热冲击性能的影响.结果表明,激光重熔工艺参数对重熔涂层的抗热冲击性能影响显著,采用合适的工艺参数(激光比能量),可以使重熔涂层获得最佳的抗热冲击性能.不同激光重熔工艺参数处理的涂层形成的组织结构不同,使得涂层的抗热冲击性能不同.合适的激光重熔工艺参数下涂层表现出高的抗热冲击性能,主要是因为重熔后的涂层组织结构有利于热应力的释放以及其相结构在高温冲击下具有良好的稳定性.     

改性玄武岩火焰喷涂粉末的制备及其性能

研究了一种新型的玄武岩火焰喷涂粉末的制备以及其性能。将天然的玄武岩矿石经过破碎、添加金属氧化物降低熔点、高温加热、水淬以及二次造粒等方法制粉,并且对不同状态的粉末的性能进行了检测。参照国家标准中的粉末的流动性及松装密度的实验标准采用霍尔流速仪对粉体的流动性及松装密度进行测量,利用扫描电子显微镜和X射线衍射分析仪研究了粉体形貌和涂层结构,利用示差扫描热量仪对各粉体进行了热分析,采用火焰喷涂工艺在45钢表面制备涂层并利用扫描电子显微镜观察了涂层的表面和截面的形貌。结果表明:经过改性后的玄武岩粉末的流动性有明显的提高,松装密度也有所增加,增强了热喷涂效果和有利于得到良好的涂层。     

普通与纳米ZrO2涂层性能对比研究

以纳米ZrO2-8wt%Y2O3,粉末(YSZ)和普通微米氧化锆粉末为原料,采用等离子喷涂工艺制备了厚度为0.8mm的纳米结构氧化锆和普通氧化锆两种热障涂层,并对涂层的结构和性能进行了研究,结果表明:在该厚度下,纳米结构涂层的结合强度低于普通涂层,而其隔热性能优于普通涂层,且热流密度越大越明显.     

K417G高温合金纳米氧化锆热障涂层的制备与性能

通过探讨喷涂工艺参数对纳米氧化锆涂层结构和性能影响的规律，使纳米氧化锆未熔颗粒基本上保持原始氧化锆粉末的纳米级晶粒大小，熔化的颗粒则起粘结剂的作用，使涂层内氧化锆颗粒问结合牢固，涂层结构致密。纳米氧化锆热障涂层与常规氧化锆涂层相比导热系数降低，隔热效果得到明显提高。力学试验结果则表明，纳米结构热障涂层在硬度、抗热冲击性能、耐冲击性以及结合强度等方面都明显高于常规粉末制备的涂层。     

等离子喷涂氧化锆涂层及激光重熔涂层的摩擦磨损性能

采用等离子喷涂制备了常规氧化锆涂层和纳米氧化锆涂层,并对制备的纳米氧化锆涂层进行了激光重熔处理,系统地研究了3种氧化锆涂层(常规、纳米和激光重熔涂层)在常温和高温下的摩擦磨损性能.结果表明,纳米氧化锆涂层耐磨性能明显优于常规氧化锆涂层,而激光重熔处理后的纳米氧化锆涂层在常温和高温下,都表现出最低的摩擦系数和最好的耐磨性能.这3种涂层的表面粗糙程度、涂层孔隙率和裂纹状况明显不同,从而表现出不同的摩擦磨损特性;说明纳米粉末等离子喷涂结合激光重熔技术是提高氧化锆涂层性能的有效方法.     

氧化锆空心球粉体制备及其涂层性能研究进展

粉体是决定等离子喷涂热障涂层性能的基本因素,本文主要介绍了高性能等离子喷涂热障涂层用氧化锆空心球粉体的制备方法及其涂层性能的相关研究。等离子球化和喷雾干燥造粒是制备氧化锆空心球粉体的两种不同方法;氧化锆空心粉体在等离子喷涂过程中更易熔化,并且在熔化后形成空心液滴;空心液滴与基体碰撞铺展过程中存在的"反溅"使其铺展凝固时间更长,形成的扁平粒子直径小,厚度均匀,缺陷少;相对于其它类型粉体,采用氧化锆空心球粉体制备的热障涂层具有适中的孔隙率,低热导率和低模量,抗高温烧结,符合高性能热障涂层的性能要求。     

氧化锆系列喷涂粉末的制备及应用

收集了100余种用于喷制热障涂层的氧化锆系列喷涂粉末的资料,总结了有关粉末供应商、粉末规格、成分、粒度分布、粉末形状、熔点和使用温度的数据,并阐述了氧化锆粉末的制备技术及其工业应用。     

粉末结构对HVOF喷涂Cr3C2-25%NiCr涂层组织及磨粒磨损性能的影响

以团聚烧结和烧结包覆两种工艺制备的Cr3C2-25%NiCr粉末为原料,运用超音速火焰喷涂(HVOF)技术制备了Cr3C2-NiCr涂层,分析比较了两种涂层的显微组织、孔隙率和硬度,运用橡胶轮磨损试验机测定了涂层在不同磨损条件下的耐磨粒磨损性能,研究了粉末制备工艺和磨损工艺条件对涂层磨损质量损失的影响。结果表明,烧结包覆粉末所沉积的涂层具有高的致密度、硬度和良好的耐磨性,而团聚烧结粉末所形成的涂层耐磨粒磨损性能较差。磨损工艺条件对涂层的磨损质量损失有很大影响,在大载荷或粗磨粒作用的工况下,涂层的磨损质量损失最大。     

等离子喷涂热障涂层的隔热性分析

采用大气等离子喷涂方法制备不同类型的氧化钇部分稳定氧化锆热障涂层：传统涂层、纳米团聚粉末制备的纳米涂层和空心球粉末制备的空心球涂层。通过扫描电镜、透射电镜、压汞仪和激光脉冲法观察和测试各种涂层的组织形貌、空隙分布和导热系数,并在相同条件下测试各种涂层的隔热性能。结果表明：纳米涂层空隙率最低,内部孔洞细小。空心球涂层组织相对疏松,内部层片更薄,有最高的空隙率和最大的平均空隙大小。传统涂层介于二者之间。纳米涂层和传统涂层均表现出双态空隙大小分布。涂层的导热系数均随着温度的上升而升高。传统涂层的热导率最高,纳米涂层与空心球涂层的热导率相接近。纳米涂层具有最好的隔热性能,空心球涂层接近纳米涂层的隔热效果。隔热效果与涂层厚度呈线性关系。随着厚度增加,导热系数低的纳米涂层和空心球涂层的隔热效果增长幅度高于传统涂层。     

纳米氧化锆涂层的制备、显微结构及抗热震性能研究

利用大气等离子喷涂技术在不锈钢基体上制备了纳米氧化锆涂层.运用XRD、SEM、TEM、拉曼光谱和金相技术等分析手段对涂层的显微结构、物相组成进行了观察与分析;利用热冲击试验测试涂层的抗热震寿命.结果表明,纳米氧化锆经喷雾造粒后的颗粒粒径主要分布在15～70 μm之间,流动性好,适合等离子喷涂,粉末和涂层的物相均由四方氧化锆组成;在喷涂过程中,喷涂工艺参数(氩气流量)有规律的地影响着涂层的显微结构,进而影响涂层的抗热震性能.     

Study of microstructure and thermal shock behavior of two types of thermal barrier coatings

Gas turbines provide one of the most severe environments challenging material systems nowadays. Only an appropriate coating system can supply protection particularly for turbine blades. This study was made by comparison of properties of two different types of thermal barrier coatings (TBCs) in order to improve the surface characteristics of high temperature components. These TBCs consisted of a duplex TBC and a five layered functionally graded TBC. In duplex TBCs, 0.35 mm thick yittria partially stabilized zirconia top coat (YSZ) was deposited by air plasma spraying and ～0.15 mm thick NiCrAlY bond coat was deposited by high velocity oxyfuel spraying. ～0.5 mm thick functionally graded TBC was sprayed by varying the feeding ratio of YSZ/NiCrAlY powders. Both coatings were deposited on IN 738LC alloy as a substrate. Microstructural characterization was performed by SEM and optical microscopy whereas phase analysis and chemical composition changes of the coatings and oxides formed during the tests were studied by XRD and EDX. The performance of the coatings fabricated with the optimum processing conditions was evaluated as a function of intense thermal cycling test at 1100 °C. During thermal shock test, FGM coating failed after 150 and duplex coating failed after 85 cycles. The adhesion strength of the coatings to the substrate was also measured. Finally, it is found that FGM coating has a larger lifetime than the duplex TBC, especially with regard to the adhesion strength of the coatings.     

热障涂层先进陶瓷材料研究进展

随着航空航天技术的不断发展,恶劣的工作环境对镍基高温合金的使用性能提出了更高的要求,热障涂层是一种应用于涡轮发动机热端部件的表面技术,通过沉积在镍基高温合金表面以降低基底表面温度。概述了传统氧化钇部分稳定氧化锆热障涂层的性能优势,包括优异的隔热性能、较高的热膨胀系数与断裂韧性。同时归纳了氧化钇部分稳定氧化锆热障涂层在高温环境下存在的问题,包括氧化锆相变与涂层烧结造成的过早失效。在此基础上,重点综述了近年来热障涂层先进陶瓷材料的研究进展,包括稀土陶瓷材料与自愈合材料,其中稀土陶瓷材料包括稀土掺杂氧化锆、成分掺杂与结构设计的稀土锆酸盐、稀土磷酸盐、3种不同结构的稀土钽酸盐、高熵稀土陶瓷材料以及稀土铌酸盐等,自愈合材料包括二硅化钼与碳化钛。针对各种热障涂层陶瓷材料,分别从热震寿命、热膨胀系数、热导率、耐腐蚀性、断裂韧性等方面进行了归纳,并总结了各材料现阶段发展的不足之处。最后展望了热障涂层材料的发展方向。     

Technical and Economical Aspects of Current Thermal Barrier Coating Systems for Gas Turbine Engines by Thermal Spray and EBPVD: A Review

The most advanced thermal barrier coating (TBC) systems for aircraft engine and power generation hot section components consist of electron beam physical vapor deposition (EBPVD) applied yttria-stabilized zirconia and platinum modified diffusion aluminide bond coating. Thermally sprayed ceramic and MCrAlY bond coatings, however, are still used extensively for combustors and power generation blades and vanes. This article highlights the key features of plasma spray and HVOF, diffusion aluminizing, and EBPVD coating processes. The coating characteristics of thermally sprayed MCrAlY bond coat as well as low density and dense vertically cracked (DVC) Zircoat TBC are described. Essential features of a typical EBPVD TBC coating system, consisting of a diffusion aluminide and a columnar TBC, are also presented. The major coating cost elements such as material, equipment and processing are explained for the different technologies, with a performance and cost comparison given for selected examples.     

Experimental and numerical life prediction of thermally cycled thermal barrier coatings

This article addresses the predominant degradation modes and life prediction of a plasma-sprayed thermal barrier coating (TBC). The studied TBC system consists of an air-plasma-sprayed bond coat and an air-plasma-sprayed, yttria partially stabilized zirconia top layer on a conventional Hastelloy X substrate. Thermal shock tests of as-sprayed TBC and pre-oxidized TBC specimens were conducted under different burner flame conditions at Volvo Aero Corporation (Trollhättan, Sweden). Finite element models were used to simulate the thermal shock tests. Transient temperature distributions and thermal mismatch stresses in different layers of the coatings during thermal cycling were calculated. The roughness of the interface between the ceramic top coat and the bond coat was modeled through an ideally sinusoidal wavy surface. Bond coat oxidation was simulated through adding an aluminum oxide layer between the ceramic top coat and the bond coat. The calculated stresses indicated that interfacial delamination cracks, initiated in the ceramic top coat at the peak of the asperity of the interface, together with surface cracking, are the main reasons for coating failure. A phenomenological life prediction model for the coating was proposed. This model is accurate within a factor of 3.     

Failure of physical vapor deposition/plasma-sprayed thermal barrier coatings during thermal cycling

ZrO₂-7 wt.% Y₂O₃ plasma-sprayed (PS) coatings were applied on high-temperature Ni-based alloys precoated by physical vapor deposition with a thin, dense, stabilized zirconia coating (PVD bond coat). The PS coatings were applied by atmospheric plasma spraying (APS) and inert gas plasma spraying (IPS) at 2 bar for different substrate temperatures. The thermal barrier coatings (TBCs) were tested by furnace isothermal cycling and flame thermal cycling at maximum temperatures between 1000 and 1150 °C. The temperature gradients within the duplex PVD/PS thermal barrier coatings during the thermal cycling process were modeled using an unsteady heat transfer program. This modeling enables calculation of the transient thermal strains and stresses, which contributes to a better understanding of the failure mechanisms of the TBC during thermal cycling. The adherence and failure modes of these coating systems were experimentally studied during the high-temperature testing. The TBC failure mechanism during thermal cycling is discussed in light of coating transient stresses and substrate oxidation.     

Erosion studies on duplex and graded ceramic overlay coatings

The solid-particle erosion resistance of ceramic thermal barrier coatings (TBCs) is of considerable economic and industrial significance. Of additional significance to the service performance of these coatings is the effort to minimize the differences in coefficients of thermal expansion between the metallic substrate and the overlay TBC. A new design strategy toward this effort is the introduction of functionally graded interlayers between the metallic and ceramic layers. This research examines the role of interlayer grading, microstructure, and thermal cycling on the solid-particle erosion behavior of partially stabilized zirconia and alumina coatings at ambient and elevated temperatures. The results point to beneficial effects of grading and processing on the elevated temperature erosion response of these deposits.     

Lanthanum hexaaluminate—a new material for atmospheric plasma spraying of advanced thermal barrier coatings

One of the main application fields of the thermal spraying process is thermal barrier coatings (TBCs). Today, partially stabilized zirconia (YSZ or MSZ) is mainly used as a TBC material. At temperatures above 1000 °C, zirconia layers age distinctively, including phenomena shrinkage and microcrack formation. Therefore, there is a considerable interest in TBCs for higher temperature applications. In this paper, lanthanum hexaaluminate, a newly developed TBC material with long-term stability up to 1400 °C, is presented. It ages significantly more slowly at these high temperatures than commercial zirconia-based TBCs. Its composition favors the formation of platelets, which prevent a densification of the coating by postsintering. It consists of La₂O₃, Al₂O₃, and MgO. Its crystal structure corresponds to a magnetoplumbite phase. Lanthanum hexaaluminate powders were produced using two different fabrication routes, one based on salts and the other one based on oxides. To optimize the granulate, various raw materials and additives were tested. The slurry was spray dried in a laboratory spray drier and calcined at 1650 °C. Using these two powders, coatings were produced by atmospheric plasma spraying (APS). The residual stresses of the coatings were measured by the hole drilling method, and the deposition process was optimized with respect to the residual stresses in the TBC. The coatings were extensively analyzed regarding phase composition, thermal expansion, and long-term stability, as well as microstructural properties.     

Influence of heat treatment on nanocrystalline zirconia powder and plasma-sprayed thermal barrier coatings

Nanostructured zirconia top coat was deposited by air plasma spray and NiCoCrAlTaY bond coat was deposited on Ni substrate by low pressure plasma spray.Nanostructured and conventional thermal barrier coatings were heat-treated at temperature varying from 1050 to 1 250oC for 2-20 h.The results show that obvious grain growth was found in both nanostructured and conventional thermal barrier coatings(TBCs)after high temperature heat treatment.Monoclinic/tetragonal phases were transformed into cubic phase in the agglomerated nano-powder after calcination.The cubic phase content increased with increasing calcination temperature.Calcination of the powder made the yttria distributed on the surface of the nanocrystalline particles dissolve in zirconia when grains grew.Different from the phase constituent of the as-sprayed conventional TBC which consisted of diffusionlesstransformed tetragonal,the as-sprayed nanostructured TBC consisted of cubic phase.     

用于热障涂层的锆酸钆材料研究进展

为了满足新型航空发动机的性能要求,需要开发出能在超高温条件下服役的热障涂层材料.近年来已有多种陶瓷材料被证实在热障涂层领域具有发展前景,在这之中,稀土锆酸盐材料有着高温下热导率较低与稳定性良好的特点,其中又以锆酸钆材料的热导率最低,热膨胀系数最高.概述了锆酸钆材料的结构特点,对其在高温下发生的有序无序转变进行了介绍,总...