飞机襟翼滑轨用钛合金表面激光熔注WC/TC4复合涂层微观组织分析

针对提高飞机襟翼滑轨表面耐磨性能的问题,采用激光熔注(Laser melt injection,LMI)技术在TC4表面制备WC颗粒增强的金属基复合材料(Metal matrix composite,MMC)层。通过光学显微镜,SEM,XRD,EDS等设备研究了MMC层微观组织和相组成以及扫描速度对熔注层形貌的影响,结果表明,扫描速度对MMC层有重要影响,随着扫描速度的增加,热输入减小,熔池内对流减弱,WC颗粒团聚现象增加。MMC层主要由WC,TiC,Ti,W_2C和W相组成,其中TiC分布主要分为两种:以反应产物的形式存在于Ti基体中;以反应层的形式存在于WC颗粒周围。反应层存在方式对WC颗粒有钉扎作用,因此耐磨性能的提升更大。除此之外,研究发现MMC层不同区域微观组织和硬度值存在明显差异:熔注层下部,TiC枝晶数量较少且尺寸较小;熔注层中上部,TiC枝晶数量较多且尺寸较大;硬度值主要与WC颗粒的分布有关,MMC层的硬度从上部到热影响区成先上升再下降的趋势。

激光熔覆耐磨自润滑覆层在发射装置上的应用研究

利用激光熔覆技术在发射装置挡件(15-5PH马氏体钢)表面制备了金属基自润滑耐磨覆层,分析了复合粉末及其激光熔覆耐磨覆层的物相组成。用扫描电镜观察了耐磨覆层横截面的显微组织;分析了试样的摩擦学性能。结果表明,挡件采用激光熔覆耐磨自润滑覆层,其强度和耐磨性满足要求,可解决挡件在导弹发射过程中的长效服役寿命问题。

High temperature frictional wear behaviors of nano-particle reinforced NiCoCrAlY cladded coatings

The NiCoCrAlY coatings strengthened by three nano-particles with the same addition were prepared on a Ni-base super alloy using laser cladding technique. The dry frictional wear behaviors of the coatings at 500 ℃ in static air were investigated. The comparison was made with the coating without nano-particles. The results show that the wear mechanism of the NiCoCrAlY coatings with nano-particles, like the coating without nano-particles, is the delamination wear due to the strong plastic deformation and oxidative wear. However, the frictional coefficient of the coatings increases and presents the decrease trend with the increase of sliding distance after adding nano-particles. Moreover, the wear rate of the coatings with nano-particles is only 34.0%-64.5% of the coating without nano-particles. Among the three nano-particles, the improvement of nano-SiC on the high temperature wear resistance of the coating is the most significant.

透明导电薄膜材料的研发态势

简述了透明导电薄膜材料的研究现状与发展趋势,特别是对目前研究比较活跃的透明导电氧化物(TCO)及金属基复合多层透明导电膜的研究动态,材料设计原理及其应用进行了重点介绍,并就透明导电薄膜材料目前存在的问题及发展方向进行了分析讨论。

Effects of TiB_2+TiC content on microstructure and wear resistance of Ni55-based composite coatings produced by plasma cladding

TiB2-TiC reinforced Ni55 matrix composite coatings were in-situ fabricated via plasma cladding on steels using Ti, B4C, and Ni55 as precursor materials at different proportions. Effects of TiB2+TiC content of ceramics phase on the microstructure and wear resistance were studied. The results showed that ceramic phases TiB2 and TiC were in-situ synthesized by plasma cladding, and the ceramic phase content significantly affected tribological performance and the wear mechanism of coatings under different loads. The composite ceramics protected coatings from further delamination wear by crack-resistance under a load of 30 N. Severe abrasive wear and adhesive wear were prevented when the load increased to 60 N because of the high hardness and strength of ceramic phases. Moreover, a compacted layer appeared on the wear surface of coatings with high content of ceramic phases, which effectively decreased the friction coefficient and wear rate. The TiB2-TiC composite ceramics significantly improved the wear performance of metal matrix composite coatings by different mechanisms under loads of 30 and 60 N.

Constrained sintering and wear properties of Cu-WC composite coatings

Coatings of metal matrix composites(Cu?WC)were fabricated by solid-state sintering.WC reinforcing particles indifferent quantities from5%up to30%(volume fraction)were mixed with Cu particles.After mixing,the powders were poured ontothe surface of copper substrates.Sintering was carried out at1000°C under a reducing atmosphere in a vertical dilatometer.Sinteringkinetics was affected by both rigid substrates and WC particles which retarded the radial and axial densification of powders.However,the coatings were strongly attached to the substrate,and WC particles were randomly distributed within the matrix.The addition ofthe reinforcing particles enhanced the microhardness and reduced the volume loss in wear tests to1/17compared to the unreinforcedsample.The predominant wear mechanism was identified as abrasion at a load of5N.20%WC(volume fraction)reinforcingparticles led to the maximum values of properties for the composite coating.

Improved wettability and mechanical properties of metal coated carbon fiber-reinforced aluminum matrix composites by squeeze melt infiltration technique

In order to improve the wettability and bonding performance of the interface between carbon fiber and aluminum matrix,nickel-and copper-coated carbon fiber-reinforced aluminum matrix composites were fabricated by the squeeze melt infiltration technique.The interface wettability,microstructure and mechanical properties of the composites were compared and investigated.Compared with the uncoated fiber-reinforced aluminum matrix composite,the microstructure analysis indicated that the coatings significantly improved the wettability and effectively inhibited the interface reaction between carbon fiber and aluminum matrix during the process.Under the same processing condition,aluminum melt was easy to infiltrate into the copper-coated fiber bundles.Furthermore,the inhibited interface reaction was more conducive to maintain the original strength of fiber and improve the fiber−matrix interface bonding performance.The mechanical properties were evaluated by uniaxial tensile test.The yield strength,ultimate tensile strength and elastic modulus of the copper-coated carbon fiber-reinforced aluminum matrix composite were about 124 MPa,140 MPa and 82 GPa,respectively.In the case of nickel-coated carbon fiber-reinforced aluminum matrix composite,the yield strength,ultimate tensile strength and elastic modulus were about 60 MPa,70 MPa and 79 GPa,respectively.The excellent mechanical properties for copper-coated fiber-reinforced composites are attributed to better compactness of the matrix and better fiber−matrix interface bonding,which favor the load transfer ability from aluminam matrix to carbon fiber under the loading state,giving full play to the bearing role of carbon fiber.

A facile method for fabrication of nano-structured Ni-Al_2O_3 graded coatings: Structural characterization

Powder charges of micron-size Ni and Al2O3were utilized to deposit nano-structured Ni-Al2O3composite coatings on analuminum plate fixed at the top end of a milling vial using a planetary ball mill.Composite coatings were fabricated using powdermixtures with a wide range of Ni/Al2O3mass ratio varying from1:1to plain Ni.XRD,SEM and TEM techniques were employed tostudy the structural characteristics of the coatings.It was found that the composition of the starting mixture strongly affects the Al2O3content and the microstructure of the final coating.Mixtures containing higher contents of Al2O3yield higher volume fractions of theAl2O3particles in the coating.Though Ni-Al2O3composite coatings with about50%of Al2O3particles were successfully deposited,well-compacted and free of cracks and/or voids coatings included less than20%(volume fraction)of Al2O3particles which weredeposited from powder mixtures with Ni/Al2O3mass ratios of4:1or higher.Moreover,mechanical and metallurgical bondings arethe main mechanisms of the adhesion of the coating to the Al substrate.Finally,functionally graded composite coatings withnoticeable compaction and integrity were produced by deposition of two separate layers under identical coating conditions.

Layered double hydroxides with larger interlayer distance for enhanced pseudocapacitance

The interlayer space of the layered materials is not always the electrochemical active area for contributing to the pseudocapacitive process. To our knowledge, few efforts have been devoted to investigating the effect of interlayer distance of layered double hydroxides（LDHs） on pseudocapacitors. Here, we obtained the CoAl-LDH with different interlayer distance via the reaction in aqueous media hydrothermally. Electrochemical characterization reveals that the CoAl（DS^-（dodecyl sulfate））-LDHs with an interlayer distance of 2.58 nm can deliver higher specific capacitance of 1481.7 F g^-1 than CoAl（SO4^2-）-LDH（0.87 nm, 1252.7 F g^-1） and CoAl（CO3^2-）-LDH（0.76 nm, 1149.2 Fg^-1） at a discharge current density of 1 A g^-1. An asymmetric supercapacitor with the CoAl（DS^-）-LDHs‖activated carbon also shows a better electrochemical performance, including a high energy density of54.2 W h kg^-1 at a power density of 0.9 kW kg^-1 and a longterm stability, in comparison with CoAl（SO4^2-）-LDH and CoAl（CO3^2-）-LDH ‖activated carbon.