等离子喷涂Al2O3陶瓷涂层的显微组织检测技术

使用自动金相制样设备和光学显微镜对大气等离子喷涂氧化铝陶瓷涂层金相样品制备技术及显微组织评估技术进行研究,确定最佳的制样及评估方法.结果表明:金相试样制备时采用树脂粘接SiC湿砂轮切割片取样、配备正确制样参数的自动化磨抛设备,采用SiC新砂纸研磨和回弹性低的无毛布抛光,能够有效呈现涂层的真实显微组织,解决了涂层孔隙率异...     

Alumina coatings by plasma spraying of monosize sapphire particles

A series of plasma sprayed coatings of controlled microstructure was obtained by spraying three monosize sapphire powders using an axial injection torch in which the plasma gas composition and nozzle diameter were the only processing parameters varied. The effects of changes in these parameters on the coating splat morphology, porosity, angular crack distribution, and hardness are reported. The uniform, dense microstructure and the high hardness of 14 GPa (a level usually only associated with chromia thermal spray coatings) of the best alumina coatings resulted from using tightly controlled processing conditions and monodispersed precursor powders. The microstructural quality of plasma sprayed coatings and, hence, the coating properties can be improved significantly by minimizing variations in processing and raw material parameters. This paper originally appeared in Thermal Spray: Meeting the Challenges of the 21st Century; Proceedings of the 15th International Thermal Spray Conference, C. Coddet, Ed., ASM International, Materials Park, OH, 1998. This proceedings paper has been extensively reviewed according to the editorial policy of the Journal of Thermal Spray Technology.     

铝镁合金等离子喷涂复相陶瓷涂层微观组织

为解决铝镁合金表面耐磨性差的问题,利用机械球磨法和PVA造粒技术制备复合陶瓷粉末,采用等离子喷涂技术在XGFH-3铝镁合金表面制备了反应复相陶瓷涂层,利用扫描电镜(SEM)、X射线衍射仪(XRD)分析了喷涂复合粉末和复相陶瓷涂层的形貌及组成.结果表明,复合粉末随着球磨时间的延长明显趋于扁平化和均匀化,并且生成了Al₃Ti,Ni₄Ti₃等新相.而在喷涂过程中Al₃Ti和Ni₄Ti₃中间相又会消失,涂层中出现了MgAl₂O₄和Ti₅Si₃等新相,基体和涂层之间有元素扩散,这使得涂层有良好的结合强度.     

Microstructural characterization of radio frequency and direct current plasma-sprayed Al2O3 coatings

Microstructures of radio frequency (RF) and direct current (DC) plasma-sprayed Al₂O₃ coatings deposited onto steel substrates were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), electron microprobe analysis (EMPA), polarizing optical microscopy (OM), and transmission electron microscopy (TEM). Because RF and DC plasmas produce different particle heating and acceleration, the morphology, phase structure, and fracture modes of the coatings vary substantially. In the case of RF coatings, a clear lamellar microstructure with relatively thick lamellae was observed, which is due to the large particles and the low particle velocities, with α-Al₂O₃ as the predominant phase and with delamination type of fracture detected on the fracture surface. In contrast, the DC coatings consisted of predominantly metastable γ-Al₂O₃ as well as amorphous phases, with a mixed fracture mode of the coating observed. In spite of limited interfacial interdiffusion detected by EMPA, TEM showed an interfacial layer existing at the interface between the coating and the substrate for both cases. For RF coatings, the interfacial layer on the order of 1 μm was composed of three sublayers, each of which was different in composition and morphology. However, the interfacial layer for the DC coating consisted primarily of an amorphous phase, containing both coating and substrate materials with or without platelike microcrystals; although in some regions a thick amorphous Al₂O₃ layer was in direct contact with the substrate.     

A comparative study of tribological behavior of plasma and D-gun sprayed coatings under different wear modes

In recent years, thermal sprayed protective coatings have gained widespread acceptance for a variety of industrial applications. A vast majority of these applications involve the use of thermal sprayed coatings to combat wear. While plasma spraying is the most versatile variant of all the thermal spray processes, the detonation gun (D-gun) coatings have been a novelty until recently because of their proprietary nature. The present study is aimed at comparing the tribological behavior of coatings deposited using the two above techniques by focusing on some popular coating materials that are widely adopted for wear resistant applications, namely, WC-12% Co, A1₂O₃, and Cr₃C₂-MCr. To enable a comprehensive comparison of the above indicated thermal spray techniques as well as coating materials, the deposited coatings were extensively characterized employing microstructural evaluation, microhardness measurements, and XRD analysis for phase constitution. The behavior of these coatings under different wear modes was also evaluated by determining their tribological performance when subjected to solid particle erosion tests, rubber wheel sand abrasion tests, and pin-on-disk sliding wear tests. The results from the above tests are discussed here. It is evident that the D-gun sprayed coatings consistently exhibit denser microstructures and higher hardness values than their plasma sprayed counterparts. The D-gun coatings are also found to unfailingly exhibit superior tribological performance superior to the corresponding plasma sprayed coatings in all wear tests. Among all the coating materials studied, D-gun sprayed WC-12%Co, in general, yields the best performance under different modes of wear, whereas plasma sprayed Al₂O₃ shows least wear resistance to every wear mode.     

晶须增韧等离子喷涂陶瓷涂层的可控制备与力学性能研究

针对新一代航空发动机和重型燃气轮机对长寿命、高韧性热障涂层的迫切需求,本文通过喷雾造粒法制备了长径比为10的ZrO2晶须复合YSZ喷涂粉末,采用SAPS技术制备了YSZ/ZrO2晶须増韧陶瓷复合涂层,对复合涂层的工艺参数进行优化,研究了熔融指数对陶瓷复合涂层微观结构的影响规律;通过狭缝法收集单个摊片的实验,阐明了ZrO2晶须增韧YSZ陶瓷涂层的形成机理,建立了晶须増韧陶瓷涂层的微观结构与热力学性能的内在关系。基于晶须弥散分布于复合涂层未熔颗粒区的特征,相比纳米结构YSZ涂层,YSZ/ZrO2晶须増韧陶瓷复合涂层的断裂韧性与热循环寿命均提高一倍。     

The characteristics of a low-power-consumption plasma jet and ceramic coatings

The effects of the composition of plasma gases (Ar-N₂, Ar-H₂), arc current, and voltage on the temperature and velocity of a low-power (5 kW) plasma torch in the arc field free region has been investigated using an enthalpy probe. Coatings of Al₂O₃-13TiO₂ were deposited under different conditions. The results show that in the Ar-N₂ plasma, the enthalpy, temperature, and velocity change little with arc current and voltage when regulating the nitrogen proportion in the plasma gas. The hardness of the resulting coatings is 800 to 900 kg/mm² HV.300. For Ar-H₂ plasma, however, increases in the H₂ content in the mixture of the gases remarkably enhanced the velocity and heat transfer ability of the plasma jet, with the result that the coatings showed high hardness up to 1200 HV.     

Effects of power level on characteristics of vacuum plasma sprayed hydroxyapatite coating

In this study, hydroxyapatite coatings were obtained with a vacuum plasma spray system at different power levels that were achieved by altering the plasma current and voltage. The effects of spray power level on coating characteristics were investigated. X-ray diffraction was used to identify the crystallinities of as-sprayed coatings, Electron Probe Microanalysis was employed to detect the surface chemical composition of as-sprayed coatings and Scanning Electron Microscopy revealed the microstructure. The results indicated that spray power greatly affected the crystallinity, chemical composition, and microstructure of as-sprayed hydroxyapatite coatings, which were linked to the melting state of hydroxyapatite powder. Presently at School of Materials Science and Engineering, Shanghai Jiaotong University, 1954 Huashan Road, Shanghai 200030, Republic of China.     

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     

Development of electrically conductive plasma sprayed coatings on glass ceramic substrates

The production of functional coatings on glass or glass ceramic substrates is of outstanding interest in modern product development due to the specific thermophysical properties of glasses, like low or even negative CTE, low heat conductivity and high dimensional stability. Atmospheric plasma spraying (APS) is an adequate technology for the deposition of a wide variety of materials on glasses and opens new application fields for thermal spraying technology in engineering and consumer industries.Metals are the frequent solution to produce electrically conductive layers in thermal spraying operations. Concerning applications with glass ceramic as a substrate, an intermediate oxide ceramic coating is applied before depositing the metallic layer, so that the distribution of residual stresses in the composite caused during and after the deposition process due to the mismatch in the materials thermophysical properties is minimized. However, the electrical properties required for the developed coatings presented in this paper can be fulfilled using other spraying materials, like mixed phases of oxide ceramics and metal powders, or pure ceramic materials. In this way, mono-layer electrically conductive systems which ensure the required stability and adhesion of the coating can be developed, reducing as well production time and costs.In the proposed approach, the three systems, metal oxide layer-composites, ceramic-metal mixed layers and ceramic mono-layers as conductive coatings on glass ceramics were thermally sprayed with APS. The coatings were characterized in terms of residual stress distribution and electrical conductivity. The influence of the process parameters on the coating electrical and mechanical properties was analyzed using the design of experiments (DOE) methodology.     

Evaporation of zirconia powders in a thermal radio-frequency plasma

Incomplete evaporation of high-melting solid precursors, such as zirconia (ZrO₂), is a major problem in the application of plasma-flash evaporation processes to powder synthesis and production of high performance coatings. The evaporation of zirconia powders injected into a thermal radio-frequency (RF) plasma is investigated by using optical emission spectroscopy (OES) and laser Doppler anemometry (LDA) to study evaporation rates and particle velocities. Model calculations are compared with the results of the process diagnostics. Axial emission profiles confirm the influence of the particle size on the evaporation behavior. Line-integrated side-on emission profiles are used to assess the rate of evaporation.     

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。     

Microstructural features and properties of plasma sprayed YPSZ/NiCrAlY thermal barrier coating (TBC)

0　IntroductionThermalbarriercoatings(TBCs)arewidelyusedontheturbinebladesforaircraftpropulsionorpowergenerationtoreducethemetallicsubstratetemperature,whichleadstoincreasingengineefficiencyandloweringpollutantemissionsresultingfromallowableincreaseofoperationtemperature[1,2].Today,TBCsareattractingmoreattentionandhavewiderpotentialapplicationstoprotecthightemperaturecomponents.However,thermalbarriercoatingshaveatendencytocrackandspallinserviceduetothermalshockandthermalcyclingbetweenambient…     

炉熔处理对等离子喷涂Ni基WC型自熔合金涂层组织形态的影响

研究了等离子喷涂Ni基WC型自熔合金涂层炉熔处理前后的组织形态。结果表明,经重熔处理后,涂层由富含孔隙,未熔颗粒的层状结构转变为致密的结晶组织结构,涂层与基材由机械咬合结合转变为冶金反应扩散结合,涂层的内聚强度和涂层／基体的结合强度都得以显著改善。涂层的相组成在重熔前后变化不大,均主要由γ-Ni固溶体相,Ni-B(Ni2B),Cr-B(CrB),Ni-Si(Ni5Si2)和WC硬质相等组成,由于等离子喷涂是一种快速凝固工艺,在喷涂态涂层中形成了部分非晶相,经重熔处理后,非晶相发生完全晶化。     

On-line temperature monitoring and process diagnosis of plasma sprayed coatings

On-line temperature monitoring of plasma sprayed coating is presented, which is based on IR pyrometery combined to robot trajectories. Temperature fields of the substrate before spraying and the deposited coating when the damage happens are taken to investigate the temperature fluctuation information. Experimental results demonstrate that coating damage always occurs in the temperature transition area of the substrate from the higher to the lower, as well as the higher temperature area. The temperature difference between the peak and the mean of the relevant regions is beyond 30-50 ℃ or even higher. This case provides the omen of coating damage and the focusing scopes for the process control of coating temperature in plasma spraying.     

The modeling of coating thickness, heat transfer, and fluid flow and its correlation with the thermal barrier coating microstructure for a plasma sprayed gas turbine application

The plasma sprya deposition of a zirconia thermal barrier coating (TBC) on a gas turbine component was examined using analytical and experimental techniques. The coating thickness was simulated by the use of commercial off-line software. The impinging jet was modeled by means of a finite difference elliptic code using a simplified turbulence model. Powder particle velocity, temperature history, and trajectory were calculated using a stochastic discrete particle model. The heat transfer and fluid flow model were then used to calculate transient coating and substrate temperatures using the finite element method. The predicted thickness, temperature, and velocity of the particles and the coating temperatures were compared with these measurements, and good correlations were obtained. The coating microstructure was evaluated by optical and scanning microscopy techniques. Special attention was paid to the crack structures within the top coating. Finally, the correlation between the modeled parameters and the deposit microstructure was studied. This paper originally appeared in Thermal Spray: Meeting the Challenges of the 21st Century; Proceedings of the 15th International Thermal Spray Conference, C. Coddet, Ed., ASM International, Materials Park, OH, 1998. This proceedings paper has been extensively reviewed according to the editorial policy of the Journal of Thermal Spray Technology.     

超音速等离子喷涂非晶涂层微观结构与摩擦学性能

采用新一代超音速高能等离子喷涂(SAPS)技术制备了Fe基和Mo基两种非晶涂层,对涂层的微观结构与摩擦学性能进行对比分析。结果表明,SAPS喷涂Fe基和Mo基非晶涂层内部孔洞少、结构致密性高。与Fe基涂层相比,具有更低孔隙率的Mo基涂层在摩擦过程中表现出更低的磨损率(1.1×10^-4 μm·N^-1·s^-1),耐磨性更优。涂层的磨损机理均以磨粒磨损和疲劳磨损为主,并伴随着磨屑氧化。     

In-flight characteristics of plasma sprayed alumina particles: Measurements,modeling, and comparison

The key phenomena controlling the properties of sprayed coatings are the heat and momentum transfer between the plasma jet and the injected particles. Modern on-line particle monitoring systems provide an efficient tool to measure in-flight particle characteristics in such a way that factors that could affect the coating quality can be identified during the spray process. In this work, the optical sensing device, DPV-2000 from Tecnar, was used for monitoring the velocity, temperature, and diameter of in-flight particles during the spraying of alumina with a Sulzer-Metco F4 plasma torch. Evolution of particle velocity, temperature, diameter, and trajectory showed well-marked trends. Relationships between the position of the in-flight particles into the jet and their characteristics were pointed out, thus delivering valuable information about their thermal treatment. Moreover, a numerical model was developed and predictions were compared with experimental results. A good agreement on particle characteristics was found between the two different approaches.     

新型铝青铜及其喷涂层中Ce元素的作用(英文)

采用一次共装熔炼、砂型铸造Al含量超过Cu-Al二元合金共析点的新型铝青铜合金Cu-14Al-4.5Fe,在45#中碳钢表面制备铝青铜等离子喷涂层。通过扫面电镜、X射线衍射分析、电子探针、透射电镜和显微硬度计分析Ce元素对新型铝青铜合金及喷涂层表面组织形貌和维氏硬度的影响。结果表明:添加0.6%Ce到铸态合金及喷涂层可以使细化的κ相均匀分布于基体,并提高材料硬度。等离子喷涂层快速凝固,保留铝青铜涂层中Fe元素的过饱和固溶体,避免生成(α+γ2)共析相。含Ce喷涂层中的堆垛层错是提高材料力学性能的因素。     

超音速等离子喷涂ZrO2涂层的缺陷分析与力学性能

采用超音速等离子喷涂技术(SAPS)在Q235钢基体表面制备了ZrO₂涂层。利用扫描电镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)分别对ZrO₂涂层微观形貌、物相组成、元素分布进行了检测和分析,同时利用维氏硬度计对ZrO₂涂层硬度进行了测量,分别得出了涂层、涂层与基体连接处、基体的硬度值。结果表明:利用超音速等离子喷涂技术所制备的ZrO₂涂层表面存在大量颗粒凸起和孔洞。涂层截面存在形状为“马蹄形”、“弯月形”、“椭球形”以及“不规则多边形”的孔洞和横向裂纹缺陷,孔隙率为13%。在高温作用下,涂层中Zr元素发生扩散,由涂层顶部至底部Zr元素含量上升,且基体表面出现少量Zr元素。涂层材料在喷涂过程中发生相变,由单斜相转为四方相。涂层、涂层与基体连接处、基体显微硬度分别为740.51、205.79、189.33 HV0.2,涂层与基体连接处相比于基体材料表面的显微硬度提高。