硬质合金上镀铜

在YG8硬质合金上得到了外观平整、质量较好的铜镀层。用扫描电镜(SEM)对镀层的表面形貌进行了分析,用加热法和划线法对镀层的结合强度进行了测试。结果表明:该镀层的表面显微硬度为216～219HV;预处理工艺对提高镀层质量有重要影响;H等离子处理改变了镀层和基体之间的结合状态,提高了镀层与硬质合金的结合强度。     

硬质合金上镀铬的研究

为提高硬质合金与金刚石膜层的结合力，在硬质合金上电沉积铬过渡层，介绍了硬质合金的镀前处理及镀铬工艺，利用扫描电镜观察了镀层表面及断面形貌，研究了H等离子处理对镀层表面、断面形貌及镀层与硬质合金结合强度的影响。结果表明，H等离子处理使得镀层与硬质合金基体相互扩散，从而明显提高了镀层与合金基体的结合强度。     

提高镀层与基体结合强度的途径

在电镀过程中影响镀层质量的因素很多,生产过程中不可避免地要出现一些质量上的问题,其中镀层与基体的结合强度就是衡量质量的重要指标之一.通过对镀层与基体结合机理及其影响因素的探讨,提出了提高镀层与基体结合强度的途径,为改善镀层的结合力提供了参考依据.     

对电刷镀镀层与基体结合强度机理的探讨

在电刷镀过程中，影响镀层质量的因素很多，实践过程中不可避免地要出现一些质量上的问题。其中镀层与基体金属的结合强度就是衡量镀层质量的重要指标之一。本文通过对镀层与基体电化学结合机理的探讨，提出了提高镀民基体结合强度的途径和方法。     

用于铝合金零件表面强化的Ni-SiO2-MoS2复合镀层的研究

在2A12铝合金基体表面制备了Ni-SiO_2-MoS_2复合镀层,拟对铝合金零件进行表面强化。测试了镀层的形貌、成分及结合力,观察了基体与镀层表面的硬度压痕和磨损面形貌,并比较了基体与镀层的显微硬度及耐磨性。结果表明:镀层表面比较平整,无孔洞等缺陷,镀层中Ni、Si和Mo的质量比为92.23∶7.08∶0.69。镀层与基体之间结合牢固。镀层表面的硬度压痕较浅,其显微硬度在4 736～5 137MPa范围内,显微硬度是基体的10倍以上。镀层具有较好的抵抗局部塑性变形的能力及耐磨性。     

弱浸蚀溶液对无氰电镀镉-钛合金镀层性能的影响

为了提高无氰电镀镉-钛合金镀层与基体的结合力,采用不同的弱浸蚀工艺对基体进行表面处理,利用场发射扫描电子显微镜及电化学工作站,观察和测试了两种不同弱浸蚀溶液对镉-钛合金镀层微观形貌、结合力及耐蚀性能的影响。结果表明,基体经过弱浸蚀后镀层完整、致密、结合力好,耐蚀性能增强。当H_2SO_4质量分数为5%,HCl质量浓度为40 mL/L时,对基体浸蚀效果较好,析氢不严重。     

渗氢对铜-锡合金镀层鼓泡缺陷的影响

采用强制充氢试验模拟27SiMn钢基体在电镀铜-锡合金过程及前处理工序中的渗氢行为。充氢后,铜-锡合金镀层上出现的鼓泡行为与在液压支架立柱上的鼓泡行为类似,说明渗氢是引起铜-锡合金镀层鼓泡的重要因素。通过测量氢渗透电流密度发现,原子态的氢容易在27SiMn钢基体中扩散,很难在铜-锡合金镀层中扩散,氢在镀层与基体的界面处的富集导致鼓泡的发生。     

镀层与基体的结合力

镀层与基体(或中间镀层)之间的结合力是镀层的重要机械性能。介绍了镀层与基体的结合力定义、影响因素及测量方法。结合生产实际举例说明镀层与基体结合力不良的危害,以及改善镀层与基体结合力的措施。分析了镀层与基体的结合力和镀层内应力的区别和联系。     

氰化镀锌析氢故障及对策

在氰化镀锌中,氢气的析出,除电能的消耗外,更主要的是氢的析出会使锌镀层质量变劣。对氢析出致使锌镀层质量变劣系统归纳分析可能产生的故障大概可划分以下几种: 1、氢脆 析出的氢能够进入锌镀层内,造成锌镀层甚至基体金属的吸氢作用,锌的吸氢大约在0.001％～0.01％之间,铁族金属吸氢约0.1％。氢在金属内使得晶格扭曲,产生很大的内应力,外观虽然看不出镀层缺陷,但其机械性能往往是不合格的。电镀锌析出的氢不仅对镀层性能产生不利的影响,有时甚至渗透到基体金属中,使其金属韧性大大降低,特别是对高强度钢、弹簧钢产生的危害更是严重的,有时导致脆断,这就是人所共知的“氢脆”现象。     

液相烧结三元硼化物硬质合金覆层材料的特性

采用原位反应真空液相烧结技术,在Q235钢基体表面制备三元硼化物硬质合金覆层,使钢基体表面获得耐磨抗蚀、界面结合强度高的覆层材料.利用扫描电镜和能谱分析对三元硼化物硬质合金和钢基体的界面微观结构和界面区元素分布进行了分析,发现硬质合金覆层和钢基体之间形成了一个具有一定厚度的过渡层,合金元素浓度没有发生突变,两相之间形成了良好的冶金结合.研究了覆层材料的显微硬度、抗弯强度与耐磨性能,结果表明:在1 200 ℃烧结,覆层的Vickers硬度达到12MPa,弯曲强度在试样受到拉伸应力与压缩应力时分别达到86.74MPa,1168.21 MPa,耐磨性与Q235钢相比有了较大提高.     

Fabrication and application of chemical vapor deposition diamond-coated drawing dies

A diamond coating has been fabricated by straight hot filament chemical vapor deposition (CVD) passing through the interior hole of the drawing die using a mixture of hydrogen and acetone as source gases. The substrates are drawing dies made by cemented carbides with large apertures (φ>2 mm), and are pre-treated by various methods including leaching Co by acid solution, scratching the substrate by diamond powder and decarburizing the WC substrate by microwave plasma. The homogeneity of coatings is estimated by scanning electron microscopy and Raman spectroscopy. The preliminary applied tests show that the adhesion strength of diamond coatings can meet the need of the practical drawing wires. As compared with the cemented carbide drawing die, the working lifetime of the diamond-coated drawing die can be increased by a factor of five to 10.     

Tribological behavior of GNPs doped Al2O3 coating fabricated by SHVOF thermal spraying on cemented carbide

This paper aims to experimentally investigate the effect of graphene nanoplatelets (GNPs) doped Al₂O₃ coating deposited on the surface of cemented carbide substrate using suspension high velocity oxy fuel (SHVOF) thermal spraying technique. Scanning electron microscopy was applied to characterize GNPs doped Al₂O₃ feedstock, the surface morphologies of cemented carbide before and after spraying, and the wear track morphology of cemented carbide after wear tests. The phases of GNPs doped Al₂O₃ feedstock, uncoated and coated cemented carbide were analyzed by X-ray diffraction. The existence of GNPs was analyzed by Raman spectroscopy. A mixture of un-molten and molten splats formed on the surface of cemented carbide substrate after SHVOF thermal spray. The average coefficient of friction (CoF) of coated samples was slightly lower than that of uncoated samples, which might be due to the friction-reduction effect of GNPs. The wear rate of the samples was one order of magnitude higher than that of the alumina ball, showing that the wear of samples was the main wear between the friction couples. The wear mechanism of uncoated sample was mainly fatigue spalling, and that of cemented carbide substrate coated with GNPs doped Al₂O₃ coating was mainly plowing and abrasive wear.     

粉末涂层陶瓷材料的涂层工艺及涂层机理

对使用Ａ２Ｏ３溶胶在硬质合金粉末表面涂层Ａ１２Ｏ３陶瓷进行了研究。重点探讨了基体粉末的表层处理、粉末涂层对Ａ１２Ｏ３涂胶的要求以及使用Ａ１２Ｏ３溶胶涂层硬质合金粉末的涂层工艺,最后,对有些硬质合金粉末引起Ａ１２Ｏ３溶胶在涂层过程中发生凝胶的凝胶机理、粉末涂层法的涂层机理进行了分析。认为硬质合金粉末对Ａ１２Ｏ３溶胶中胶体粒子的离子氛围的影响是使溶胶发生凝胶与否的关键。涂层机理则是硬质合金粉末表面通过     

The effect of tungsten buffer layer on the stability of diamond with tungsten carbide–cobalt nanocomposite powder during spark plasma sintering

WC–Co nanocomposite powder produced by spray pyrolysis–continuous reduction and carbonization technology, diamond coated with tungsten (W) by vacuum vapor deposition and uncoated diamond were used in this study. This work adopted the spark plasma sintering (SPS) process to prepare diamond-enhanced ultrafine WC–Co cemented carbide composite material. The effects of W buffer on the stability of diamond with WC–Co nanocomposite powder during SPS were investigated. Results showed that the uncoated diamond was mechanically embedded in WC–Co cemented carbide matrix, while the diamond coated with tungsten was combined chemically with WC–Co cemented carbide matrix. Moreover, there was a transitional layer between the diamond and the matrix which could improve the thermal stability of the diamond, prevent carbon atom of the diamond from dissolving in Co phase and increase the bonding strength of the interface between the diamond and the matrix.     

聚氨酯-硬质合金YG8双层涂层的抗磨蚀性能研究

采用聚氨酯喷涂技术和电火花熔覆技术,在基体铸钢0Cr13Ni5Mo表面制备聚氨酯-硬质合金(YG8)双层涂层,表层为聚氨酯涂层,底层为电火花熔覆层YG8;采用扫描电子显微镜(SEM)观察底层熔覆层与基体铸钢结合面的横截面形貌图,发现熔覆层由白亮层、过渡层组成,表面光亮粗糙,与基体冶金结合;并进行磨擦磨损实验和冲蚀实验。结果表明,双层涂层有较小的摩擦系数,抗冲蚀性是基体抗冲蚀性的3.87倍。该双层涂层兼有软、硬涂层的优点,适用于关键零部件的表面防护和二次修复。     

钨粉与碳化硼为原料原位合成碳化钨涂层的组织及耐磨性研究

采用钨极氩弧堆焊设备,通过原料粉末之间的高温冶金反应,在堆焊过程中原位合成碳化钨金属陶瓷涂层。对所制备的涂层试样的组织结构进行了观察分析,并且研究了涂层的耐磨料磨损性能。研究结果表明,在钨极氩弧为热源的条件下,能获得性能较好的高温涂层,为碳化钨复合涂层在工业中的实际应用提供了理论基础。     

Fatigue strength of diamond coating-substrate interface assessed by inclined impact tests at ambient and elevated temperatures

The effect of two different treatments of cemented carbide substrates, prior to the deposition of a nanocrystalline diamond (NCD) coating, on the film interface fatigue strength was investigated at ambient and elevated temperatures. The first substrate treatment of the cemented carbide substrate was a selective chemical Co-etching and the second one the deposition of a Cr-adhesive layer. Inclined impact tests at 25 °C and 300 °C were performed on the NCD coated specimens. The related imprints were evaluated by confocal microscopy measurements and EDX micro-analyses. The thermal residual stresses developed in the film structure at various temperatures were estimated by Finite Element Method (FEM) calculations. A fatigue damage in the NCD coating interface region was induced by the repetitive impacts. After this damage, the compressive residual stresses in the NCD film are released leading to its lifting from the substrate (bulge formation) and subsequent coating failure. The NCD film-substrate interface fatigue behavior is significantly affected by the test temperature. Based on the attained results at diverse substrate treatments, Woehler-like diagrams were developed for monitoring the fatigue failure of NCD coating interface area at 25 °C and 300 °C. The interfacial fatigue strength worsens as the impact test temperature grows in both examined substrate treatment cases. Moreover, Co-etched substrates compared to coated ones by an adhesive Cr-interlayer possess higher interfacial strength at ambient and elevated temperatures. These phenomena were investigated and related explanations are described in the paper.     

Effects of TiMoTa nano-crystalline interlayer on nucleation,adhesion and tribological behaviors of diamond coating

To investigate the influence of the transition layer on diamond nucleation and growth, the TiMoTa multi-alloy interlayers were firstly prepared on WC-6%Co cemented carbide by double glow plasma surface alloying technique, and diamond was then deposited using microwave plasma chemical vapor deposition system. The thickness of the TiMoTa interlayers increased from 1.2 μm to 2.7 μm with the deposition temperature increasing from 800 to 900 °C. Due to the formation of nano-crystalline structure and hard phase, the as-prepared TiMoTa interlayer exhibited high micro-hardness. In the diamond deposition process, the nano-carbide particles preferentially formed at the TiMoTa interlayers can effectively prevent the further diffusion of C, so the surface carbon concentration rapidly accumulates to the critical value required for the nucleation and growth of diamond microcrystals. Finally, a microscale wear-resistant diamond coating with good adhesion was grown on the transition layer, the crack propagation radius of the diamond coating is ～162 μm, and can reach Hf 2–3 grade. Therefore, our prepared TiMoTa nano-crystalline interlayer provides a new path for the development of a high-quality diamond coating with good adhesion on cemented carbide.