NiCrSiBC alloy: microstructure and hardness of coatings processed by arc and laser

The processing technique is decisive for the characteristics of a coating. This is because the heat supply, which depends on the technique and on the parameters, has an influence on the dilution and the solidification rate. In alloys with low metallurgical complexity, the effect of processing with deposition techniques that give a higher cooling rate may be translated into refining of the microstructure. A more refined microstructure is expected to result in higher mechanical strength of the coating. However, in the deposition of alloys that are more complex metallurgically this does not always occur, because the high cooling rate may suppress formation/precipitation of phases responsible for strength. The influence of processing on the microstructure and hardness of coatings of alloy Colmonoy-6^® was assessed in this study. The alloy was processed by plasma transferred arc and high-power diode laser on plates of AISI 304 with two levels of dilution. In both cases, good-quality, defect-free coatings were obtained. Increase in Fe content (dilution) and different cooling rates result from processing with different parameters and techniques. This leads to significant changes in microstructure and hardness of the coatings, associated with the distribution, morphology and chemical composition of the carbides and particularly of the borides.     

金属钨箔膜的制备研究进展

具有体密度的高表面质量金属钨薄膜对材料高压状态方程研究具有十分重要的意义.综述了钨箔膜制备的几种方法,包括化学气相沉积、物理气相沉积、机械轧制、机械研磨抛光、化学抛光和电解抛光.综合比较后认为,采用电解抛光法可以基本满足状态方程靶用钨箔膜的需要.电解抛光可以制备表面质量比较高,厚度最小可达几微米的金属箔材,密度与原料相同,而且不会产生内应力、表面硬化、表面沾污问题,是制备低表面粗糙度、具有块材组织结构和密度材料的一种重要手段.     

沉积温度对硬质合金金刚石涂层附着力影响的研究

采用压痕实验、扫描电镜与激光Raman光谱分析,实验研究了酸浸硬质合金基底上金刚石涂层的附着力随沉积温度的变化.结果表明,涂层质量随沉积温度降低而显著恶化,涂层应力则随沉积温度提高而上升.从提高涂层附着力的角度考虑,存在一个最佳沉积温度.在较低的沉积温度下,涂层自身的质量较低、力学性能较差,在载荷作用下易于破坏.提高沉积温度,涂层自身的质量可得到改善,但基底中的钴向基底表面扩散的倾向加大,而且热应力增大,会严重降低涂层与基底的附着力.除硬质合金基底的预处理工艺外,沉积工艺对金刚石涂层的组织、性能以及附着力均有重要影响.     

钼薄膜制备技术研究

具有体密度的高表面质量金属钼薄膜对材料高压状态方程研究具有十分重要的意义。本文介绍了制备钼薄膜的几种方法,包括:机械轧制、机械研磨抛光、化学气相沉积、电子束蒸发、脉冲激光沉积和磁控溅射。综合比较后认为,采用磁控溅射法制备的钼膜可以基本满足状态方程靶用钼(Mo)薄膜的需要。通过磁控溅射沉积方法可以制备出表面质量高,厚度可达几微米的金属Mo薄膜,其组织结构和密度接近块材而且薄膜表面不易出现硬化、沾污等问题。     

Chemical Vapor Deposition and Atomic Layer Deposition of Coatings for Mechanical Applications

Chemical vapor deposition (CVD) of films and coatings involves the chemical reaction of gases on or near a substrate surface. This deposition method can produce coatings with tightly controlled dimensions and novel structures. Furthermore, the non-line-of-sight-deposition capability of CVD facilitates the coating of complex-shaped mechanical components. Atomic layer deposition (ALD) is also a chemical gas phase thin film deposition technique, but unlike CVD, it utilizes “self-limiting” surface adsorption reactions (chemisorption) to control the thickness of deposited films. This article provides an overview of CVD and ALD, discusses some of their fundamental and practical aspects, and examines their advantages and limitations versus other vapor processing techniques such as physical vapor deposition in regard to coatings for mechanical applications. Finally, site-specific cross-sectional transmission electron microscopy inside the wear track of an ALD ZnO/ZrO₂ 8 bilayers nanolaminate coating determined the mechanisms that control the friction and wear.     

Modeling and evaluation of curved layer fused deposition

Fused deposition modeling (FDM), one of the rapid prototyping techniques is a promising technology for rapid manufacture of end use parts direct from CAD files and with the proliferation of cheaper machines, is likely to play a vital role in future polymer processing, challenging traditional processes such as injection moulding in some cases. Research evidence suggests that the road and layer structures would have significant influences on the mesostructure and consequent mechanical behaviour of the resulting polymer part. While adaptive slicing and other deposition schemes have been attempted for different reasons, it is believed that an appropriate deposition scheme is essential to ensure the best inter-road and interlayer connectivity, resulting in a continuous network of polymer chains, as in the case of the traditional processes. The current research proposes the curved layer deposition for FDM, in particular for thin shell-like parts, to ensure fibre continuity. Mathematical models are developed for curved slicing, implemented in a few case studies, parts are printed, and test results suggest marked improvement in the mechanical characteristics of curved layer parts.     

Lead alloys for permanent anodes in the nonferrous metals industry

This paper reviews the common lead alloys associated with insoluble anodes in different metal deposition operations. Metallographic techniques were used to evaluate microstructures as they relate to physical and mechanical properties. Alloy additions and manufacturing processes are examined as appropriate methods to meet the performance needs of a lead anode.     

Wire based additive layer manufacturing: Comparison of microstructure and mechanical properties of Ti-6Al-4V components fabricated by laser-beam deposition and shaped metal deposition

The microstructure and the mechanical properties of Ti-6Al-4V components, fabricated by two different wire based additive layer manufacturing techniques, namely laser-beam deposition and shaped metal deposition, are presented. Both techniques resulted in dense components with lamellar α/β microstructure. Large ultimate tensile strength values between 900 and 1000 MPa were observed. The strain at failure strongly depends on the orientation, where highest values up to 19% were obtained in direction of the building direction. Heat treatment increased the highest strain at failure up to 22%. The fatigue limit was observed to be higher than 770 MPa.     

Interface growth morphologies in pulsed laser deposited, room temperature grown multilayer hard coatings

The mechanical behaviour - hardness, elasticity, and adhesion - of multilayer coatings is strongly influenced by the type of the formed interfaces between the different layers. In industrially applied tribological coatings the interface region is predominantly not a perfect sudden change of the chemical composition of the adjacent crystal planes, but a transition zone of a thickness, which is strongly dependent on the energetic conditions during deposition. Multilayer coatings grown by high-energetic deposition techniques always struggle with high atomic mixing of both adjacent coating materials due to high energetic ion implantation.One of these high-energetic deposition techniques is the Pulsed Laser Deposition (PLD), characterized by pulsed and within one pulse alternating high- and low-energetic particle fractions, hitting successively the substrate surface. Such deposition conditions were shown to be highly advantageous for low temperature deposition by the densification of the growth structures due to activated diffusion and re-sputtering, but increases the difficulty in depositing multilayer structures.The current paper addresses these specific growth conditions based on Ti/TiN and Cr/CrN multilayer coatings. High resolution transmission electron microscopy results show that the atomic mixing at the interface is not highly critical for the deposition of multilayer coatings and that extremely dense growth structures are forming even in the interface regions.     

真空泵喷嘴加工新工艺分析

喷嘴是真空泵的核心,本文对生产实践中摸索形成的喷嘴加工工艺进行了阐述。重点对喷嘴、喷嘴前部、喷嘴锥管部分以及辅助工具的设计等加工工艺进行了总结,为喷嘴的机械加工提供了依据。     

Cold Spray Deposition of Freestanding Inconel Samples and Comparative Analysis with Selective Laser Melting

Cold spray offers the possibility of obtaining almost zero-porosity buildups with no theoretical limit to the thickness. Moreover, cold spray can eliminate particle melting, evaporation, crystallization, grain growth, unwanted oxidation, undesirable phases and thermally induced tensile residual stresses. Such characteristics can boost its potential to be used as an additive manufacturing technique. Indeed, deposition via cold spray is recently finding its path toward fabrication of freeform components since it can address the common challenges of powder-bed additive manufacturing techniques including major size constraints, deposition rate limitations and high process temperature. Herein, we prepared nickel-based superalloy Inconel 718 samples with cold spray technique and compared them with similar samples fabricated by selective laser melting method. The samples fabricated using both methods were characterized in terms of mechanical strength, microstructural and porosity characteristics, Vickers microhardness and residual stresses distribution. Different heat treatment cycles were applied to the cold-sprayed samples in order to enhance their mechanical characteristics. The obtained data confirm that cold spray technique can be used as a complementary additive manufacturing method for fabrication of high-quality freestanding components where higher deposition rate, larger final size and lower fabrication temperatures are desired.     

Structure and properties of silver-containing a-C(H) films deposited by plasma immersion ion implantation

In this study, we have grown silver-containing hydrogenated (a-C:H) and non-hydrogenated (a-C) amorphous carbon coatings by two plasma immersion ion implantation methods: I) chemical vapor deposition of methane combined with pulsed filtered cathodic arc deposition of silver, and II) by alternating arc pulses from graphite and silver in a dual cathodic arc plasma source. This unique “bias selective” feature of the deposition system allowed the deposition of silver with the substrates at ground and avoided the sputtering of the grown a-C film. Chemical composition of the samples was analyzed by acquiring their compositional depth-profiles using radio-frequency Glow Discharge Optical Emission Spectroscopy (rf-GDOES), while the microstructural properties were analyzed by X-ray absorption near edge spectroscopy (XANES) and Raman spectroscopy. In this contribution, we compare mechanical and biomedical properties by means of nanoindentation and cell viability tests, respectively, of a-C(H) films obtained by two different plasma immersion ion implantation techniques.     

A critical review of diamond like carbon coating for wear resistance applications

In recent years innovation in carbon based materials have encouraged both researchers as well as industrialists to develop materials/composites with improved tribological properties. Researchers have been fascinated to develop diamond like carbon (DLC) or carbon nanotubes (CNTs) reinforced coatings to their good corrosion resistance, excellent wear resistance, good adhesion strength, and self -lubricious nature. The present review article is mainly focused on various techniques employed in order to process DLC/CNTs coatings as well as provide a summary of DLC/CNTs deposition on different substrates. The present study includes major types, properties and tribological behavior of carbon based materials and mechanisms involved in coating deposition. The study also discusses that deposition of DLC/CNTs coatings on the substrate materials enhances the wear, corrosion and mechanical properties of the substrate.     

信号处理和虚拟仪器技术在无损检测中的应用

无损检测技术的发展及应用对机械工程发展具有重大意义。介绍了数字图像处理、人工神经网络、多传感器信息融合技术以及虚拟仪器技术在无损检测中的应用情况。     

Additive Manufacturing of PLA and CF/PLA Binding Layer Specimens via Fused Deposition Modeling

As one of the most popular additive manufacturing techniques, fused deposition modeling (FDM) is successfully applied in aerospace, automotive, architecture, and other fields to fabricate thermoplastic parts. Unfortunately, as a result of the limited nature of the mechanical properties and mass in raw materials, there is a pressing need to improve mechanical properties and reduce weight for FDM parts. Therefore, this paper presents an experiment of a special polylactic acid (PLA) and carbon fiber (CF)/PLA-laminated experimental specimen fabricated using the FDM process. The mechanical properties and mass analysis of the new composites for the PLA and CF/PLA binding layer specimen are investigated experimentally. Through the experimental analysis, one can conclude that the mass of laminated specimen is lighter than the CF/PLA specimen, and the tensile and flexural mechanical properties are higher than the pure PLA specimen.     

仿形加工控制中快速A／D转换方法与数据处理

针对计算机控制仿形加工系统中电器干扰和机械振动较严重的情况，设计并给出一种与ＣＰＵ并行动行的高性能Ａ／Ｄ轮换方法、优化的数据滤波程序和流程图，对于快速和抗干扰系系统的数据采集具有实用参考价值。     

Properties of nanostructured cubic boron nitride films prepared by the short-pulse laser plasma deposition techniques

Nanostructured cubic boron nitride (BN) films were synthesized on molybdenum substrates by using the short-pulse laser plasma deposition techniques. The surface morphologies, chemical compositions, bond structures, and mechanical properties of the obtained BN thin films have been investigated by scanning electron microscopy, Raman scattering, Fourier transform infrared spectroscopy (FTIR), energy dispersive spectra, and hardness measurements. High power density laser deposition yielded boron-rich BN nanorod arrays where tBN component dominates. Reducing power density down to 8 × 10⁷ W/cm² during laser plasma deposition produced flat cBN thin films. Typical TO and LO bands in the Raman and FTIR spectra of the cBN samples were identified. The cBN sample with hardness up to 40 GPa was obtained.     

Gas phase deposition of diffusion barriers for metal substrates in solid oxide fuel cells

One way to improve the mechanical properties of solid oxide fuel cells is the development of metal supported designs. This type of SOFC offers improved thermal shock resistance, reduced temperature gradients due to the greater thermal conductivity of the metal, and lower operating temperatures. Switching from ceramic supports to metal supports also allows the uses of conventional metal joining and forming techniques and could significantly reduce the material and manufacture costs. However, one persistent problem needs to be solved: inter-diffusion of chemical elements contained in the metal substrates and in the anodes of SOFC leads to degradation, which is to be prevented by protective coatings. In order to address the issues of sintering and delamination for metal supported SOFC, the deposition of gadolinia doped ceria on metal substrates made of Crofer 22 APU has been done by electron beam evaporation and reactive spray deposition technique, as two direct deposition techniques that will not require a sintering step, respectively. Additionally, the effect of ion-assistance on layers made by electron beam evaporation was studied. Because metal supported fuel cells aim at low/intermediate operating temperatures, reducing the thickness of these protective coatings is crucial, since layer thickness is directly correlated to its ohmic resistance. A layer of nickel was applied by magnetron sputtering to prove the effectiveness of the deposited diffusion barrier layers.     

Measurement of residual stresses by X-ray diffraction techniques in MoN and Mo2N coatings deposited by arc PVD on high-speed steel substrate

Polycrystalline MoN and Mo₂N films have promising physical and mechanical properties, which made them candidates for wear- and corrosion-resistant coatings and diffusion barriers in microelectronics. The residual stresses in MoN and Mo₂N films consist of thermal and growth stresses or intrinsic stress generated during deposition. Residual stresses in the MoN and Mo₂N coatings deposited by arc PVD techniques on HSS substrate were measured by XRD using the Rocking and the Fixed Incidence Multiplane (FIM) techniques. Residual stresses measured by both techniques in Mo₂N (face center cubic, f.c.c.) and in MoN (hexagonal) films were about 5 and 10 GPa (compressive), respectively. These results indicated that residual stresses in the MoN film was two times greater than the residual stresses in the Mo₂N film.     

退火处理及沉积方向对激光沉积TA15钛合金性能和组织的影响

以TA15钛合金粉末为原料,利用激光沉积制造方法制备TA15钛合金拉伸试样厚壁件。通过光学显微镜(OM)、扫描电子显微镜(SEM)和X射线衍射(XRD)等方法研究退火温度及沉积方向对TA15钛合金组织、拉伸性能的影响,以及α相变形机制。结果表明：随着退火温度升高,显微组织中α相长宽比呈上升趋势;激光沉积成形TA15钛合金厚壁件在沉积和垂直沉积方向上的力学性能存在差异,沉积方向上的抗拉强度明显均低于垂直沉积方向上的抗拉强度;柱状晶晶界对α片层的受力变形有一定的阻碍作用;α片层通过挤压变形和滑移变形两种机制发生变形或断裂;两种方向上拉伸断裂方式不同,沿沉积方向上断裂为韧性断裂,沿垂直沉积方向上断裂为半解理半韧性断裂。