金刚石涂层刀具的研究进展

针对CVD金刚石在刀具上主要应用类型,着重介绍了金刚石涂层刀具的研究进展与现状.论述了基体材料的选择,以及分析了硬质合金金刚石涂层刀具的技术特点,并指出了进一步深入研究的方向.     

涂层梯度硬质合金的研究进展

主要综述了涂层梯度硬质合金的发展,对涂层梯度硬质合金基体的制备、基体涂层技术、基体表层碳含量的控制等进行了阐述.展望了梯度硬质合金的前景和发展方向.     

MoS2软涂层刀具的基体材料优选及涂层制备

以常见的几种高速钢和硬质合金为基体材料，运用有限元软件分析了基体表面MoS2软涂层的残余热应力。结果表明：高速钢表面涂层的最大残余热应力小于硬质合金表面涂层的残余热应力；涂层与基体之间弹性模量和热膨胀系数等参数及沉积温度的差异是影响涂层残余热应力大小的主要因素。采用中频磁控溅射加离子束辅助沉积工艺制备了两种MoS2软涂层刀具并对其性能进行了测试，分析结果符合有限元计算的结论。     

WC-Co硬质合金/CVD金刚石涂层刀具研究现状

化学气相沉积(Chemical vapor deposition,CVD)金刚石涂层刀具具有高硬度、优异的耐磨性、良好的冲击韧性和化学稳定性,能满足高效率、高精度的加工要求,逐渐成为切削铝和高硅铝合金、碳纤维增强复合材料及石墨等轻质量高强度难加工材料的主流涂层刀具。基于WC-Co硬质合金为基体的CVD金刚石涂层刀具在切削加工过程中容易发生CVD金刚石涂层的剥落,自主研发结合性能优良、长时间加工稳定的WC-Co硬质合金/CVD金刚石涂层刀具仍是该领域国内外发展的必然趋势。目前,研究者为了提高WC-Co硬质合金/CVD金刚石涂层刀具的结合性能,采用化学刻蚀法和机械处理法相结合去除WC-Co硬质合金基体表层中的Co粘结相,发现其能增强涂层与基体的结合强度,但基体表层Co粘结相含量的减少容易导致基体中形成脆化层,降低基体的强度和韧性。为了减少基体的强度和韧性损失,研究者在WC-Co硬质合金基体和金刚石涂层之间制备稳定的含Co中间化合物或沉积中间层,成功阻挡Co粘结相的热扩散。除了上述方法外,研究者还通过调控金刚石涂层工艺参数和结构,将微米晶与纳米晶金刚石层叠相结合,来提高金刚石涂层刀具的摩擦学...     

电热爆炸定向喷涂WC-Co涂层实验研究

采用电热爆炸定向喷涂技术在45钢基体上制备了WC-17%Co硬质合金涂层.利用扫描电镜和能谱仪对涂层显微组织进行了分析,借助纳米硬度计测定了涂层的硬度和弹性模量.研究结果表明:涂层组织细小均匀,涂层致密,孔隙率低;涂层与基体结合良好,界面附近存在元素扩散现象,涂层与基体为冶金结合;涂层弹性模量在210GPa-250GPa之间;涂层硬度达到17.1GPa,为原始硬质合金硬度的1.3倍左右,远远高于其他传统喷涂层硬度.     

梯度纳米硬质涂层内部应力的有限元分析

利用有限元分析法模拟计算硬质涂层Ti、TiN、TiCN和TiAlN在不同情况下所受应力状态分析。结果表明:涂层上所加载的应力越大,涂层内部残余应力越大,造成的涂层损坏也越严重;在同种基体合金情况下TiCN涂层比TiN涂层相对抗压性能较好;同一种结构硬质涂层镀在高速钢基体上较镀在硬质合金基体上耐热性较好;涂层厚度的增加导致涂层所受残余应力减小,增了基体的抗静载压力,提高了基体的抗压性;同种涂层在不同温度下工作时,温度越高,所受的残余应力越大。     

采用溶胶-凝胶法在刀具表面制备MoS2软涂层的研究

在成功地采用柠檬酸溶胶-凝胶法在硬质合金试样表面制备出MoS2软涂层的基础上,采用扫描电镜形貌观察和摩擦系数测定等实验方法研究了MoS2加入量对涂层表面微观形貌及其摩擦性能的影响规律。结果表明,采用溶胶-凝胶法在1.6mol/L柠檬酸水溶液中分别添加13、20和27g/L MoS2粉末条件下,应用刷涂法均可以在硬质合金试样表面得到与基体结合牢固、表面质量较高的MoS2软涂层。所获得的MoS2软涂层的表面形貌呈片状。MoS2软涂层的存在明显地降低了硬质合金试样的摩擦系数,由硬质合金试样的0.58～0.86降低到软涂层的0.18～0.23。而具有不同MoS2加入量的软涂层间的摩擦系数相差不大。软涂层试样的摩擦系数明显低于硬质合金试样的原因与涂层中存在有摩擦系数低、承载力大等优良性能的MoS2以及软涂层的存在改变了原摩擦副材料间的性质等因素有关。     

变温状态下硬质合金涂层的腐蚀及摩擦磨损性能

WC-10Co4Cr与NiCr-Cr3C2等硬质合金涂层具有很强的防腐蚀性能和耐磨性能,常被应用于各类腐蚀磨损环境中.为研究温度变化对硬质合金涂层腐蚀性能及摩擦磨损性能的影响,采用超音速火焰喷涂工艺在304不锈钢基体上制备了WC-10Co4Cr和NiCr-Cr3C2硬质合金涂层,利用XRD、电化学测试以及滑动磨损测试等...     

强电流直流伸展电弧法制备硬质合金微型工具的SiC过渡层和金刚石涂层

采用强电流直流伸展电弧化学气相沉积(HCDCA CVD)技术在硬质合金微型工具表面沉积了SiC涂层作为过渡层,并在此基础之上制备了金刚石涂层。实验结果表明,采用HCDCA CVD技术在硬质合金表面制备的SiC纳米涂层连续、致密;此过渡层可有效地抑制硬质合金基体中Co的外向扩散,确保在不进行酸蚀去Co预处理的情况下,金刚石涂层对硬质合金基体具有良好的附着力。切削检测的结果表明,实验所制备的SiC过渡层/金刚石涂层的微型铣刀与未涂层微型铣刀相比,切削刃没有切削屑的粘结,且加工后的工件表面上毛刺较少。这些结果表明,SiC过渡层/金刚石涂层硬质合金微型工具将具有优异的加工性能。     

金属陶瓷生产的粉末冶金技术

金属陶瓷材料粉末冶金技术主要包括金属陶瓷材料粉末冶金技术的超细硬质合金、特殊硬质相硬质合金、梯度功能硬质合金、硬质合金热处理、涂层硬质合金、新技术和新工艺及新装备,以及Ti（C,N）基金属陶瓷等内容。     

超细粉体表面包覆技术研究进展

表面包覆技术可以有效解决超细粉体稳定性低及分散性差等缺点,并通过复合赋予其新的物理、化学等特殊功能。本文以固相包覆法、液相包覆法、气相包覆法分别较详细论述了当前超细粉体表面包覆技术的研究进展,并对常用的表面包覆方法进行了介绍。     

Development and Characterization of Cr3C2–NiCr Coated Superalloy by Novel Cold Spray Process

The coating deposition by cold spray process depends upon the mechanical properties of both the coating and substrate materials. This results in variation of the coating microstructure for different coating–substrate system materials. In this study cold sprayed 75%Cr₃C₂–25%(Ni–20%Cr) coating–superalloy system is developed. The microstructure of the coating obtained is suitable for restricting the penetration of corrosive species toward the substrate. The techniques of X-ray diffraction (XRD), scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX), and elemental X-ray analysis were used for characterization of the newly developed cold spray coated superalloy.     

Nanoparticle dispersion-strengthened coatings and electrode materials for electrospark deposition

Advanced electrode compositions were developed using self-propagating high-temperature synthesis (SHS). Electrospark deposition (ESD) was applied to produce tribological coatings which were disperse-strengthened by incorporation of nanosized particles. Nanostructured electrodes of cemented carbides were produced using powder metallurgy technologies. They allow increasing the coatings density, thickness, hardness, Young's modulus and wear resistance. Positive effects of the nanostructure of electrodes on the deposition process and structure and properties of the coatings are discussed. In that case the tungsten carbide phases become predominant in the coatings. A mechanism of the dissolution reaction of WC with Ni at the contact surface of electrode was proposed. It was shown that the formation of the coating structure starts on the electrode and is accomplished on the substrate.     

Abrasive wear behaviour of powder flame sprayed coatings on steel substrates

The main purpose of thermal spraying method is to produce wear resistant surfaces. Easy applicability, very low possibility of metallurgical changes and low distortion of coated parts due to low heat transfer to the substrate and salvation of worn parts are some of the practical advantages of this process. In this study, abrasive wear behaviour of powder flame sprayed coatings on steel substrates has been investigated. Coating was carried out onto both hot and cold substrates by using four types of powders. Prior to the wear tests, the coated specimens were machined on a lathe and surface roughness and hardness measurements were carried out on the machined surfaces. Heating the substrates prior to the coating led to the decrease in the hardness of the coating layers. Abrasive wear resistance of flame sprayed coatings was seen to be dependent on the chemical composition and characteristics of coating materials and coating condition.     

磁控溅射沉积MCrAlY涂层技术研究

MCrA1Y（M=Fe，Ni，Co等）涂层是一种合金包覆涂层，用于防止燃气轮机涡轮部件的氧化和腐蚀。已经大规模用于沉积MCrA1Y涂层的技术有电子束物理气相沉积（EBPVD）、三极溅射、低压等离子喷涂（LPP）等。在一台专用装置上对磁控溅射沉积（MSD）MCrA1Y涂层进行了研究。结果表明MSDMCrA1Y涂层成分容易调整控制，涂层纯度高，涂层致密性和涂层厚度均匀性问题都比较容易解决；这些都比EBPVD或LPPS好。MSD的MCrA1Y涂层表面粗糙度远比LPPSMCrA1Y低。MSD的主要缺点是沉积速率低，但设备结构比较简单，制造工业规模的生产装置比较容易，可以弥补这个缺点。     

雷达隐身技术的研究现状及其展望

叙述了雷达隐身技术的工作原理、类型及研究现状,综述了雷达吸波涂层中使用的吸收剂、胶粘剂和助剂,并介绍了以聚氨酯为胶粘剂的涂层基体,对聚氨酯复合材料进行了展望.回顾了雷达吸波材料的研究和发展,介绍了雷达吸波材料若干新的发现、性能及应用,同时展望了雷达吸波材料的发展趋势和研究发展的重点.     

Effect of smooth,porous and fractal surface structure on the properties of an interface

Recently, biomaterials research has focused on the creation of new materials. Mixing or doping of well-tried materials should aim to result in new physical or chemical properties, better tissue tolerability and improved long-term stability. We present another way of improving performance: the application of new technologies to well-known materials. The surface structure of a coating depends on the deposition technique. Hence, the transfer of, for example, sputtering technology to biotechnology may solve current problems with well-tried materials. This paper reports the influence of surface structure and area on the properties of pacemaker electrodes. Smooth electrodes were compared with porous electrodes produced by sintering and with fractal electrodes resulting from physical vapour deposition of iridium or titanium nitride. Micrographs revealed a slight enlargement of the surface area by sintering and an enormous enlargement with fractal coating. Analysis of electrochemical properties proved the advantages of fractal coating: the impedance spectra exhibited incomparable low impedances for frequencies down to 1 Hz and no after-potentials could be detected. Clinical results confirmed the superiority of fractal electrodes. The stimulation thresholds were significantly reduced, P-and R-wave amplitudes were increased, and ventricular evoked responses and monophasic action potentials were able to be measured with clarity unknown so far.     

Adhesion enhancement of sol-gel coating on polycarbonate by heated impregnation treatment

The main limitation in using coated plastics for optical components, electronic applications and display systems is the softness of the substrate surfaces, which is responsible for the low impact and abrasion resistance and weak adhesion between the coating and the substrate. In this paper, we report a new strategy for surface pre-treatment of plastics using heated vacuum equipment and sol-gel materials to provide both chemical bonds and penetrated hard layer into the plastic surface to increase the overall performance of the coated plastic components. The heated vacuum treatment process involves: (1) surface cleaning and pore opening by heating and vacuum conditions, (2) impregnation of hydrolyzed hybrid precursor into polymer substrate under pressure and elevated temperature, (3) aminolysis of diffused precursor with surface to form chemical bonds and hardened surface layer, (4) formation of chemical bonds at treated surface with sol-gel hard coating. An impregnation depth of 1.5 µm was detected. Water contact angle dropped to below 40° and roughness increased after treatment. These provided better adhesion by increased wettability and contact area. Much increased nanoindentation hardness and Young's modulus after impregnation provided a gradient in mechanical properties between soft substrate and hard sol-gel coating. The hardened substrate delays the plastic deformation in substrate during pencil scratch test, thereby preventing early gouge failure. Both the better adhesion and the delayed gouge failure contributed to the increased scratch resistance from 6B to 8H after sol-gel coating.     

Novel alginate based coatings on Mg alloys

Coatings on yttrium doped magnesium (Mg4Y) alloy substrates were prepared using alginate hydrogels by dip coating method to improve the surface bioactive properties of the substrate. Furthermore, composite coatings containing nano-sized calcium phosphate corresponding to hydroxyapatite (HA) phase entrapped within alginate hydrogel were also synthesized on the Mg4Y substrates. Surface characteristics of these coated substrates have been investigated using FTIR-ATR, SEM and EDS. The results show that the coatings with alginate alone are not stable in vitro; however, incorporation of NanoCaPs slightly improves the stability of these coatings. In addition, these composite coatings showed cell attachments with fibronectin incorporation. These results indicate that alginate hydrogels have the potential to be used as bioactive coating materials for different biofunctional applications.     

Modelling of the scratch resistance of particle filled sol-gel coatings on aluminium

Sol-gel derived coatings with 12 nm and 0.5-10 μm silica fillers were prepared on aluminium to evaluate the effect of particle size and filler content on coating properties The measured maximum crack-free thickness and hardness strongly depended on the type of particles used and the filler volume fraction. The scratch resistance primarily depended on coating thickness and much less on the mechanical properties of the coating. This finding was interpreted via modelling of the stresses under the scratching stylus. It was established that the initial yield occurred in the substrate for most of the coatings and the load needed for this initial yield had a relatively small dependence on the coating properties but it was strongly influenced by the coating thickness.