W、Mo、Re基体熔盐电沉积Ir涂层初探

采用熔盐电沉积法在W、Mo、Re基体表面分别制备了Ir涂层,通过扫描电镜和能谱分析了涂层的形貌和成分,对比研究了W、Mo、Re在熔盐电沉积Ir涂层过程中的性质。结果表明：W和Mo在氯化物熔盐体系中腐蚀严重,电沉积后在基体和涂层之间形成了含有腐蚀产物的夹盐层,大大降低了涂层和基体之间的结合力,在热应力和外力的作用下涂层易...     

钼基体上真空等离子体喷涂钨涂层的研究

采用真空等离子体喷涂(VPS)技术制备出厚度超过0.8 mm的金属钨涂层,并对涂层进行了高温热处理.结果显示:金属钨涂层主要呈层状结构,其密度可达到理论密度的98%以上;工艺参数对喷涂涂层性能有较大影响,特别是对涂层密度、结合强度有影响;高温热处理引起界面结构变化,形成钨钼混合层,且再结晶形成细小的晶粒;和CVD方法以及常压等离子体喷涂方法制备的钨涂层相比,低压等离子体喷涂具有明显的优势.     

双向脉冲电镀工艺参数对Na2WO4-ZnO-WO3熔盐镀钨层织构的影响

采用双向脉冲电镀工艺镀钨,并对工艺参数影响镀钨层织构进行研究.首次采用(222)不完整极图对钼片基体上的钨镀层织构进行研究.结果表明:钨镀层具有为{001}<110>织构;工艺条件的变化对镀层织构的影响主要体现在织构的散漫程度随着脉冲周期和迭加直流分量的增加而增加.金相和SEM观察均表明镀层为微观不平整表面,并借助表面的数据对钨镀层的形貌进行解释.     

发动机用TiAl表面双辉等离子制备W-Mo合金层及其高温氧化行为

目前采用双辉等离子表面合金化技术在TiAl合金表面制备W-Mo涂层的研究不多。通过SEM与XRD等测试手段,研究双辉等离子表面合金化技术在TiAl基体表面制得的W-Mo合金涂层在780℃温度下的氧化行为。研究结果表明:W-Mo改性合金在初期氧化阶段快速氧化增重,经过100 h氧化后,试样增重5.2 mg/cm2,有效改善了TiAl基体的高温抗氧化性能。W-Mo合金涂层对氧气扩散起到阻碍作用,使TiAl基体抗高温氧化性能获得显著提升。氧化处理后合金涂层表面未发生改变,形成了致密、均匀的氧化膜层。TiAl基体经100 h氧化后表面氧化膜主要是一种柱状晶结构,TiAl基体氧化产物包括金红石型TiO2以及刚玉2种成分。     

Chemically vapour deposited diamond coatings on cemented tungsten carbides: Substrate pretreatments, adhesion and cutting performance

Chemical vapour deposition (CVD) of diamond films onto Co-cemented tungsten carbide (WC-Co) tools and wear parts presents several problems due to interfacial graphitization induced by the binder phase and thermal expansion mismatch of diamond and WC-Co. Methods used to improve diamond film adhesion include substrate-modification processes that create a three-dimensional compositionally graded interface. This paper reviews substrate pretreatments and adhesion issues of chemically vapour deposited diamond films on WC-Co. The combined effect of pretreatments and substrate microstructure on the adhesive toughness and wear rate of CVD diamond in dry machining of highly abrasive materials was analyzed. The role of diamond film surface morphology on chip evacuation in dry milling of ceramics was also investigated by comparing feed forces of coated and uncoated mills. The overall tribological performance of diamond coated mills depended on coating microstructure and smoothness. The use of smother films did allow to reduce cutting forces by facilitating chip evacuation.     

Improving the structural quality and adhesion of functional coatings

In this paper a method of improving the structural quality and adhesion of functional coatings due to the pulsed mode of operation of a vacuum arc plasma source is described. The experiments were carried out by producing a carbon-based coating on a molybdenum substrate by spraying a graphite cathode in the benzene vapors. Plasma flow control is provided by alternating connection of two power sources, which allows variable closure of electron and ion currents on the substrate. This mode of operation allows to alternate the mode of heating and active diffusion of particles into the substrate with the mode of their deposition, as well as to provide the process of formation and annealing of the coating layers.     

Adhesion Enhancement of Diamond Films on Various Substrates by Carbide Interlayer

Diamond films were prepared on various substrates by a combustion flame technique using an oxyacetylene torch. During the deposition, a carbide interlayer was formed between the surface of the substrate and deposited diamond. The hard interlayers were seen on the molybdenum, tungsten as well as silicon substrates. The adhesion of diamond on the molybdenum substrate was improved with increase in the hardness of the carbide layer. This result strongly supports the premise that the carbide interlayer and/or carbon diffused layer enhances the adhesion of diamond to substrates.     

Effects of shroud gas injection on material properties of tungsten layers coated by plasma spraying

Coated tungsten layers on stainless steel substrates were are produced by atmosphere plasma spraying. A shroud gas injection method was employed to reduce the ambient air entrainment into the plasma jets. The effects of shroud gas on the material properties of the tungsten layers were investigated by finding the dependence of oxide content, coating thickness and porosity on the injection velocity, shielding width, and mass flux of the shroud gas. The high injection velocity was more effective than thick shroud shielding in protecting the plasma jets from ambient air engulfment, and the mass flux of the shroud gas showed negligibly small effects on the suppression of air entrainment. Therefore, in order to produce a thick tungsten coating with low porosity and oxide contents, high injection velocity with a limited flow rate is a desirable operating condition for shroud gas injection in atmospheric plasma spraying.     

Polishing of polycrystalline diamond by hot nickel surface

A microwave plasma technique has been employed to deposit polycrystalline diamond film over a molybdenum substrate button using a gas mixture of hydrogen and methane at a substrate temperature of 851°C. A CVD diamond coated molybdenum substrate button was mounted with a load against hot nickel plate and rotated for 3.45 h in a hydrogen ambient. Hot tungsten filament was used as a heat source to maintain the temperature of the nickel block and CVD diamond coated molybdenum button at 848°C. This experiment has reproducibly shown the successful polishing of polycrystalline CVD diamond by hot nickel. A Tencor profilometer and scanning electron microscope have been used to evaluate the surface smoothness and morphology before and after polishing the polycrystalline diamond thin films.     

DEPOSITION OF DIAMOND FOR CUTTING TOOL APPLICATIONS

The poor adhesion of diamond film to substrates is one of the major problems for practical use in a cutting tool (1-4). in this study, sintered tungsten carbide (WC) body without Co metal, not cemented carbide, was used as the substrate (5), and the effects of surface decarburization of the substrate for improvement in the adhesion of diamond films were investigated. The surface decarburization and diamond coating were carried out in a microwave plasma CVD system. From the results of several adhesion tests, including the cutting tests, it is concluded that the good adhesion is obtained by surface decarburization of the substrate before diamond coating. The reasons for improvement in adhesion are considered by observing the interface structure between the film and the substrate. The damage mechanism of diamond coating on cutting an AI-18%Si alloy with increasing cutting speed is also discussed.     

薄膜结合强度的刮剥式测量方法

本文介绍了一种薄膜结合强度的新型测量方法～刮剥法的测量原理、特点以及应用范围。所谓薄膜结合强度的刮剥式测量方法（简称刮剥法），实际上是一个使用特制刮剥刀具、以类似于薄层金属刮削方式工作，并以从基底上剥离薄膜所需能量作为其结合强度量度的测量方法。刮剥法与现广泛使用的划痕式结合力测量法的区别主要表现为：（１）该法是一个能量测量方法，即以薄膜的剥离能量作为薄膜与基体的结合强度的描述；（２）测量时采用的是对膜／基界面的切向加载方式；（３）测量结果是对膜／基结合强度的直接描述，并对基底表面状态、材质等不敏感；（４）可以对其它方法无法进行测量的超硬材料薄膜，如金刚石和立方氮化硼等，进行结合强度测量。本文通过对刮剥过程中刮剥刀刃附近区域的受力分析，得出了成功实现沿界面剥离薄膜的必要条件以及刮剥法测试对试样的要求和应用范围。     

一种高效沉积反应室的设计

利用Arrhenius公式对化学气相沉积的反应进行研究，设计了一种低压热化学气相沉积（LPCVD）高效沉积反应室。在料管的下方与衬底的上方间安放漏斗型筛板，在工艺中有效地提高了氢气的分压，并有利于衬底温度的提高，加快了沉积速率。通过对设计前后钨薄膜的金相组织对比分析后发现，较高的沉积速率可以使沉积薄膜晶粒细小，结构致密，但薄膜与衬底附着力较差，提高衬底温度可有效地提高薄膜与衬底附着力，以弥补因较高的沉积速率带来的薄膜与衬底附着力较差的问题，提高薄膜质量。     

超音速火焰喷涂制备纳米和微米结构WC-η涂层的耐熔锌腐蚀性能

以钨氧化物、钴氧化物和炭黑为原料, 通过原位还原碳化反应制备纳米WC-η(η为Co₃W₃C、Co₆W₆C等缺碳相)复合粉, 粉末平均粒径为155 nm。该复合粉经团聚造粒制备得到具有高致密性和良好流动性的热喷涂粉末。以此纳米结构和商业化的微米结构低碳WC-12Co粉末作为喂料, 通过超音速火焰喷涂制备硬质合金涂层。结果表明, 纳米结构涂层中生成了一定量等轴状的W₂C相, 裂纹主要沿晶界或相界面扩展, 而微米结构涂层中除W₂C外还含有较多的W相, 主要包裹在WC颗粒表面, 穿晶断裂比例较高, 裂纹扩展路径较平滑。由于纳米结构涂层组织致密、晶粒细小、界面积大, 因此比微米结构涂层具有更高的硬度和断裂韧性。两种涂层在熔融锌液中浸泡200 h后, 微米结构涂层中产生了较多的横向和纵向裂纹, 导致材料的大面积剥落和基材腐蚀; 纳米结构涂层中没有发生锌的浸蚀, 在局部产生了少量纵向裂纹, 裂纹间隙被钨钴氧化物所填充, 反而抑制了熔锌对涂层的腐蚀, 因此纳米结构涂层表现出更高的耐熔锌腐蚀性能。     

铝合金内表面电爆炸喷涂不同比例钼-高碳钢的性能对比研究

为了提高铝合金工件内表面的耐磨损能力,采用电爆炸喷涂技术在LY12基体上进行了制备钼和80号高碳钢复合涂层的实验研究.通过钼/高碳钢交替喷涂制备了钼和高碳钢的喷涂次数比分别为1:1和1:2的复合涂层,并对涂层进行了检测.结果表明,电爆炸喷涂的复合涂层形成了良好的冶金结合,涂层具有硬度高、抗磨损、粗糙度小、结合强度好的优点,层数比为1:2时涂层的性能更加优越.     

高强涂层结合强度的评价--楔形加载法

提出用楔形和载法评价高强度涂层材料与基体的结合强度。该方法利用楔形压头置于有楔形槽的试样中,使楔形压头中心线与涂层基体界面重合,施加静态载荷至试样沿涂层界面开裂,根据试样受力边界条件,给出涂层与基体结合强度的公式。对三种不同涂层的基体材料进行了结合强度试验。结果表明,用楔形加载法可对高强涂层与基体的结合强度进行测试,所得数据分散度与ASTMC633－79标准相同,试验数据不受非随机因素的影响。     

Effects of substrate material on diamond growth from CO-H2 plasma

Diamond synthesis from CO-H₂ plasma has been carried out on various substrate materials, e.g. metals: nickel, cobalt, tungsten, molybdenum, copper and ceramics: SiC, SiO₂, Al₂O₃, ZrO₂, AlN. Diamond formation was confirmed on every substrate with the exception of cobalt and nickel. The highest density of diamond nucleation, over 10⁸ cm^–2, was obtained on amorphous SiO₂, the carbide-forming metals tungsten and molybdenum and on SiC; on these the nucleation density was one order of magnitude higher than on the other substrates. Diamond films prepared on tungsten, molybdenum and SiC substrates had a strong adhesion force: 1.3 to 1.5 kg mm^–2.     

WC基热喷涂金属陶瓷涂层的激光改性研究

本工作研究了CO2激光重熔处理对超音速火焰喷涂WC--Co和WC--NiCr涂层的组织结构和摩擦学行为的影响。结果表明：选定优化参数下,激光重熔可降低涂层气孔率,提高涂层显微硬度,涂层与基材之间实现冶金结合;干摩擦条件下,涂层经过激光重熔处理耐磨性能显著提高;但润滑条件下劣于未经重熔处理涂层,这可能与未重熔涂层含有较多的气孔,可存储润滑油较好地发挥润滑效果有关。     

Coated WC powders by sputtered nanostructured Ni and stainless steel

The efficiency of the powder surface modification depends on their surface characteristics. Sputtering has been revealing an important skill for the coating of powders with metal and metal alloys, with important consequences on the surface properties. However, some modifications in the holder of this particulate substrate have obliged to set up some changes in a non-conventional sputtering system. The aim of the present work is to demonstrate the efficiency of the prototype developed and the influence of deposition parameters in the quality of coated powders; tungsten carbide powders and austenitic stainless steel (SS) and nickel targets have been selected. These types of materials are used in tungsten carbide parts/devices as binders to promote the technological process; as coatings they decrease the interparticle friction reducing the pressure of shape forming as well as the temperature of sintering process.     

物理气相沉积黄铜镀层对钛丝绳和橡胶粘合性能的影响研究

利用物理气相沉积（PVD）在钛丝绳表面沉积黄铜镀层,研究了钛基体表面处理、黄铜镀层成分、镀层厚度以及镀层形貌对钛丝绳和橡胶粘合力的影响。结果表明,有效去除钛基体表面钝化层并采用打底过渡层方式,可以提高黄铜镀层和钛基体的结合力;钛丝绳和橡胶粘合力随着黄铜镀层中Zn含量的升高而增加,Zn≥30%时进入增长平台区;镀层厚度增加会降低钛丝绳和橡胶粘合力,而膜层表面粗糙度增大则有利于粘合力的提高。      

Diamond deposition on Mo with thermal stress buffer layer coated mild steel substrate by combustion flame CVD

In order to develop wear resistance diamond/molybdenum (Mo) hybrid coating process can be conducted in open air. Diamond deposition on the molybdenum with thermal stress buffer layer coated mild steel substrate by the combustion flame chemical vapor deposition (CFCVD) was carried out. As the thermal stress buffer layer, atmospheric plasma sprayed Mo/Fe mixture coating was deposited between Mo top coat and mild steel substrate. Consequently, crack generation and peeling off of the coating occurred due to thermal influences on the condition of Mo coated mild steel substrate in our previous study, diamond particles could be created on the Mo coating without fracture and peeling off. Besides, an additional Mo coating after diamond deposition increases the adhesion force between the diamond coating and the initial Mo coating. This encapsulation of the diamond particles between two Mo layers dramatically improves the resistance of the global coating making it strong enough to resist to the wearing test. These results demonstrate the high potential of thermal sprayed coating for the wear resistance improvement.