Effect of multi-walled carbon nanotubes as reinforced fibres on tribological behaviour of Ni–P electroless coatings

After multi-walled carbon nanotubes (MWNTs) were modified and dispersed uniformly in electrolyte, the MWNTs composite coatings were prepared by electroless deposition. Hardness tests were carried out using a Vickers Hardness indenter. The friction and wear behavior of the Ni–P–MWNTs composite coatings in carbon-steel rings were investigated by using a ring-on-plate wear tester at pure liquid paraffin. Moreover, the friction and wear behavior of nine kinds of wear combinations, which were composed of plates and rings of different composite coatings, were studied. The experimental results indicated that addition of MWNTs would result in an increase in microhardness and an improvement of tribological properties of the Ni–P composite coating significantly. The Ni–P–MWNTs composite coatings revealed lower wear rate and friction coefficient compared with Si–C composite coatings. Moreover, the wear combination, which composed of the Ni–P–MWNTs composite coatings, showed a more excellent ability of friction-reduction and wear resistance than other combinations, and their friction coefficient and wear rate were 0.1087 and 1.49 × 10^− 6 kg/m, respectively.     

Study on Tribological Properties of Carbon/Aramid Fabric Coatings Modified by Boron Nitride of Single Layer

Carbon/aramid fabric composite coatings modified with boron nitride of single layer were fabricated through a dip-coating method. The composite coatings were cured with successive heating processes in an oven. The friction and wear properties of those as-prepared coatings were studied on a block-on-ring tester. The obtained results showed that the wear life of the coatings increased obviously after inclusion of boron nitride of single layer; however, the values of friction coefficients of the coatings almost remained constant. The optimal loadings of boron nitride of single layer in our experiments was 5 wt.%, and the wear life of the modified coating increased by ca. 360% compared with that of pristine fabric composite coating. The worn morphology of the sliding surface for both pristine fabric coating and the composite coatings filled with boron nitride of single layer was discussed, and the wear mechanisms were illuminated.     

Effect of specimen orientation and heat treatment on electroless Ni-PTFE-MoS<Subscript>2</Subscript> composite coatings

In this study, the effects of simultaneous co-deposition of polytetrafluoroethylene (PTFE) and MoS₂ particles on tribological properties of electroless nickel (EN) coating were studied. The influences of specimen orientation and heat treatment on EN-PTFE-MoS₂ composite coatings were also investigated. Scanning electron microscopy was used to study the morphology of coatings and the distributions of the lubricant particles in the deposits. Chemical analyses of coatings were done by electron dispersive spectrometry. The phases of the coatings were identified by X-ray diffraction utilizing CuKα radiation. Wear and friction properties of the coatings were also determined by pin-on-disk wear tester. The wear investigations showed that the EN-PTFE-MoS₂ composite coating performs better than EN-PTFE and EN-MoS₂ coatings in terms of friction coefficient and wear resistance. PTFE and MoS₂ contents of the EN-PTFE-MoS₂ coating were increased by changing the specimen orientation from vertical to horizontal configuration, which leads to enhancement in tribological properties of the coating. After heat treatment, the wear rate of EN matrix composite coating decreased with corresponding change in phase structure.     

YSZ/MoS2 self-lubricating coating fabricated by thermal spraying and hydrothermal reaction

Thermal sprayed ceramic coatings have extensively been used in components to protect them against friction and wear. However, the poor lubricating ability severely limits their application. Herein, yttria-stabilized zirconia (YSZ)/MoS₂ composite coatings were successfully fabricated on steel substrate with the combination of thermal spraying technology and hydrothermal reaction. Results show that the synthetic MoS₂ powders are composed of numbers of ultra-thin sheets (about 7 ~ 8?nm), and the sheet has obvious lamellar structure. After vacuum impregnation and hydrothermal reaction, numbers of MoS₂ powders, look like flowers, generate inside the plasma sprayed YSZ coating. Moreover, the growing point of the MoS₂ flower is the intrinsic micro-pores of YSZ coating. The friction and wear tests under high vacuum environment indicate that the composite coating has an extremely long lifetime (>?100,000 cycles) and possesses a low friction coefficient less than 0.1, which is lower by about 0.15 times than that of YSZ coating. Meanwhile, the composite shows an extremely low wear rate (2.30?×?10^?7 mm³ N^?1 m^?1) and causes slight wear damage to the counterpart. The excellent lubricant and wear-resistant ability are attributed to the formation of MoS₂ transfer films and the ultra-smooth of the worn surfaces of hybrid coatings.     

A novel biomedical TiN-embedded TiO2 nanotubes composite coating with remarkable mechanical properties,corrosion, tribocorrosion resistance,and antibacterial activity

Tribocorrosion is a severe problem in dental implants, artificial joints, and other implants, and it will affect the long-term safety of the implants. To improve the deficiencies of titanium alloys, we combined physical vapor deposition technology and anodic oxidation to prepare TiN to embed TiO₂ nanotube composite coatings (NTNTs-TiN). Results show that the hardness of the NTNTs-TiN composite coatings reaches 33.2 ± 0.6 GPa, and the grains of the composite coatings were further refined. The NTNTs-TiN coating has the smallest average coefficient of friction (0.22) during tribocorrosion. The tribocorrosion resistance of NTNTs-TiN coating in SBF is increased by ∼44 and ∼2 times compared with Ti6Al4V alloy and TiN coating, respectively. The capillarity effect of the lower contact angle of NTNTs-TiN can form a continuous water-lubrication film at the interface between the counter-ball and coating and produce a lubrication film composed of Ca, Mg, and P, which reduces the coefficient of friction significantly. The NTNTs/TiN composite coating exhibits the best synergistic effect of wear and corrosion. In addition, the NTNTs-TiN coating also exhibits excellent antimicrobial and corrosion properties, which provides a new solution for the long-term safe use of implants in the human body.     

Tribological behavior of the polyamide composite coating filled with different fillers under dry sliding

The polyamide (PA) composite coating filled with the particles of microsized MoS₂, microsized graphite, and nano‐Al₂O₃, respectively, were prepared by flame spraying. The friction and wear characteristics of the PA coating and composite coating filled with the varied content of filler under dry sliding against stainless steel were comparatively investigated using a block‐ring tester. The morphologies of the worn surfaces and transfer films on the counterpart steel ring were observed on a scanning electron microscope. The result showed that the addition of fillers to the composite coatings changed significantly the friction coefficient and wear rate of the coatings. The composite coatings filled with a low level content of fillers showed lower wear rate than did pure PA coating under dry sliding; especially the MoS₂/PA composite coating had the lowest wear rate among these composite coatings. The composite coatings with a high level content of fillers had higher wear rate than did pure PA coating, except of the Al₂O₃/PA composite coating. The bonding strengths between the polymer matrix and fillers changed with the content of the fillers, which accounted for the differences in the tribological properties of the composite coatings filled with the varied content fillers. On the other hand, the difference in the friction and wear behaviors of the composite coatings and pure coating were attributed to the difference in their worn surface morphologies and transfer film characteristics. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Effects of Ta content on the oxidation and high-temperature tribological behaviors of (Zr,Ta) N coating deposited by double-cathode glow plasma alloy

ZrN-based coatings have attracted significant attention due to their high hardness and outstanding thermal properties. In this research, ZrN, TaN, and (Zr, Ta) N coatings with different Ta content (ZrTaN-1 coating with 30 at.% Ta content and ZrTaN-2 coating with 60 at.% Ta content) were prepared with a double-cathode glow plasma alloy (DGPA). The influence of Ta content on the phase composition, microstructure, mechanical performance, oxidation and tribological behaviour of the coatings was comparatively studied. The results illustrated that the (Zr, Ta) N coatings with different Ta content crystallized in NaCl-type structures. The lattice constants of the (Zr, Ta) N coatings decreased with increasing Ta content because the Ta–N bonds (0.227 nm) were shorter than the Zr–N (0.230 nm) bonds, which confirmed that Zr was successfully substituted with Ta. The oxidation resistivity of the (Zr, Ta) N coatings exhibited minimum mass gain values of 0.55 mg/cm², 5.12 mg/cm², and 17.08 mg/cm² at 650~850 °C with a Ta content of 60 at.%. The addition of Ta effectively reduced the thermal stress of the coatings and avoided cracking and peeling at high temperatures. In addition, high-temperature tribological experiments showed that the wear rate of the (Zr, Ta) N coatings at 500 °C was low and stable and was only 32.9% of that of the ZrN coating under the same conditions. This was attributed to the formation of a dense (Zr, Ta)-rich oxide on the coating surface.     

Preparation and Tribological Properties of Polyamide 11/Graphene Coatings

Polyamide 11/graphene coatings were prepared through a spraying method with as-prepared organophilic graphene. The tribological results showed that the wear life of composite coatings was obviously higher than that of neat Polyamide 11 coating; however, the values of friction coefficients had hardly changed. The optimal content of graphene in the range of our experiments was 0.4 wt%, and the wear life of the composite coating increased by 460%–880% compared with that of pristine Polyamide 11 coating. The morphology of worn surface for both pristine Polyamide 11 and the composites coatings was studied, and the wear mechanisms were discussed.     

A comparative investigation on microstructure evolution and wear resistance of in situ synthesized NbC,WC, TaC reinforced Mo2FeB2 coatings by laser cladding

To improve the microhardness and wear resistance of Mo₂FeB₂ coatings, composite coatings were prepared by laser cladding using in situ synthesized NbC, WC, and TaC. The influence of different carbides on the morphology, microstructure, microhardness, residual stress, and tribological properties of the composite coatings was investigated. The results showed various microstructural morphologies in different composite coatings. Apparent herringbone structures were observed in most coatings except for the Mo₂FeB₂/TaC composite coating and a eutectic structure was formed in the Mo₂FeB₂/WC composite coating. In addition, the heat-affected zone was typically composed of acicular martensite and lath martensite. The microhardness of the Mo₂FeB₂/WC composite coating increased to 1543.6 HV_0.5 compared with 985.7 HV_0.5 observed for the Mo₂FeB₂ coating. Tensile stress existed in the coating, bonding zone, and heat-affected zone, whereas the substrate exhibited compressive stress. The Mo₂FeB₂/WC composite coating exhibited the lowest tensile stress (298 MPa). The Mo₂FeB₂/WC composite coating containing WC and the W₂C phase had the lowest coefficient of friction (0.38) and wear rate (3.90 × 10^?5 mm³/Nm), indicating its excellent tribological properties. Moreover, the wear mechanism of the Mo₂FeB₂ coating is severe adhesive and abrasive wear. The adhesive wear mechanism was mitigated by the formation of in situ synthesized NbC, WC, and TaC. The wear mechanism of the Mo₂FeB₂/WC composite coating was only a slight abrasive wear.     

硼化钽增强聚醚醚酮复合涂层的制备及性能评价

采用阴极电泳沉积技术在纯钛基板表面沉积聚醚醚酮（PEEK）/硼化钽（TaB₂）复合涂层。采用透射电子显微镜、扫描电子显微镜、X射线衍射仪和摩擦磨损试验机等方式对电泳沉积液分散性、PEEK/TaB₂复合涂层表面形貌、微观结构、结晶行为、摩擦学性能和生物学性能进行表征。结果表明，通过调节电泳沉积参数可以制备形貌均匀、具有一定厚度的PEEK/TaB₂复合涂层，在390 ℃热处理后，涂层均匀致密无孔隙；热处理可以提高PEEK/TaB₂涂层的结晶性能，TaB₂颗粒的加入使PEEK涂层获得更高的结晶度；添加较低含量的TaB₂颗粒时，复合涂层在小牛血清（fetal bovine serum，FBS）介质中表现出良好的摩擦学性能，与纯PEEK涂层相比，磨损率分别下降了48.1 %，69.1 %；但过量TaB₂颗粒在PEEK基质中出现明显的团聚现象， 摩擦系数和磨损率呈现上升趋势；细胞实验表明，TaB₂良好的生物活性促进了样品表面细胞增殖。     

Cathode plasma electrolytic deposition of Al2O3 coatings doped with SiC particles

Semiconductor particles doped Al₂O₃ coatings were prepared by cathode plasma electrolytic deposition in Al(NO₃)₃ electrolyte dispersed with SiC micro- and nano-particles (average particle sizes of 0.5–1.7?µm and 40?nm respectively). The effects of the concentrations and particle sizes of the SiC on the microstructures and tribological performances of the composite coatings were studied. In comparison with the case of dispersing with SiC microparticles, the dispersion of SiC nanoparticles in the coatings was more uniform. When the concentration of SiC nanoparticles was 5?g/L, the surface roughness of the composite coating was reduced by 63%, compared with that of the unmodified coating. Friction results demonstrated that the addition of 5?g/L SiC nanoparticles reduced the friction coefficient from 0.60 to 0.38 and decreased the wear volume under dry friction. The current density and bath voltage were measured to analyze the effects of SiC particles on the deposition process. The results showed that the SiC particles could alter the electrical behavior of the coatings during the deposition process, weaken the bombardment of the plasma, and improve the structures of the coatings.     

Modification of Cu‐PE‐PTFE composite coatings on rubber surface by low‐energy electron beam dispersion with glow discharge

Polytetrafluoroethylene (PTFE) composite coatings doped with copper acetate and polyethylene (PE) were fabricated on rubber substrate by electron beam dispersion technique. The effects of dopant nature and glow discharge treatment on morphology, structural and tribological properties of the coatings were investigated. The results showed that Cu and PE doping change the surface structure of PTFE‐based composite coatings due to the chemical reactions between the dispersion products. Cu‐PE‐PTFE coatings show the columnar and layered growth models without and with discharge treatment. Cu adding decreases the crystallinity, branched degree and unsaturated degree of PE coatings, but increases the branched degree and unsaturated bonds in the PE‐PTFE coatings. Glow discharge enhances the crystallinity and ordering degree of composite coatings. Friction experiments indicated the significant difference of composite coatings in the nature of their destruction during friction. PE‐PTFE coating is characterized of the brittle fracture with clear failure boundaries but Cu‐PE‐PTFE coating shows a rough surface without cracking and delaminating after friction. Cu doping increases the dynamic coefficient of friction of PE and PE‐PTFE composite coatings, but discharge plasma decreases the dynamic coefficient of friction. Cu‐PE‐PTFE composite coating after discharge treatment has the decreased dynamic coefficient of friction and improved wear resistance. POLYM. ENG. SCI., 58:103–111, 2018. © 2017 Society of Plastics Engineers     

Electrical explosion spray of Ag/C composite coating and its deposition behavior

Ag–C composite coating exhibits excellent electrical and thermal conductivities, good arc mobility, and low contact resistance, making it has a good prospect in switch contact of high voltage isolators. At present, the electro-deposition method is mainly used to prepare Ag/C composite coatings. However, the production efficiency of the electro-deposition method is low and the obtained coatings are thin. The electrical explosion spraying, due to its simplicity and high efficiency, has attracted significant attention in coating preparation. In this study, a new method that confines Ag and graphite powders in a tube for electrical explosion spraying was proposed. Powder electrical explosion spraying was used for preparing an Ag/C composite coating by employing a self-designed device. The heating behavior of the powder during exploding, macroscopic morphology, micromorphology, deposition efficiency, and thickness of the coatings, as well as the deposition behavior of the sprayed particles, were investigated. After a single spraying, a dense and uniform Ag/C composite coating was obtained at the charging voltage of 13 kV and a spray distance of 18 mm. The results show that the coating area is approximately 39.25 mm², the coating thickness was 50 μm, and the deposition efficiency was 35%. the coatings have good adhesion with the substrate. the interface between the coating and the substrate appeared as an inter-diffusion of elements, which was typical of a metallurgical bonding interface. Graphite is evenly distributed in the coating. Furthermore, the underlying deposition behavior of the coating was carefully characterized.     

Influence of different introduction modes of metal Ag into plasma sprayed Al2O3 coating on tribological properties

Al₂O₃ coating and Al₂O₃/Ag (10%) composite coating were prepared on the surface of GH4169 superalloy by the atmospheric plasma spraying technology. And an in-situ synthesis method was applied to introduce the Ag particles into a part of Al₂O₃ coatings to obtain Al₂O₃/Ag(synthesis) composite coating. Then, the microstructure and mechanical properties of these three Al₂O₃-based coatings were systematically studied in this work. In order to reveal the lubrication characteristics of Ag, their friction tests were carried out at room temperature (RT), 400 °C, 600 °C and 800 °C, respectively. The results showed that both microstructure and mechanical properties of Al₂O₃/Ag(synthesis) composite coating were better than that of Al₂O₃/Ag (10%) composite coating because many pores and cracks produced during the direct spraying. Although the friction coefficients of two kinds of composite coatings were close to that of Al₂O₃ coatings at RT, their wear rates were both greatly decreased due to the introduction of Ag. In addition, the lubricating performance of Ag was not enough to reduce their friction coefficients when friction temperature is lower than 600 °C. However, the friction coefficients of these composite coatings were both reduced to about 0.3 at 800 °C . At this time, the Al₂O₃/Ag(synthesis) composite coating also exhibited a lower wear rate because of its dense microstructure and excellent mechanical properties.     

Tribological application of carbon nanotubes in a metal-based composite coating and composites

Ni-P-carbon nanotube (CNT) composite coating and carbon nanotube/copper matrix composites were prepared by electroless plating and powder metallurgy techniques, respectively. The effects of CNTs on the tribological properties of these composites were evaluated. The results demonstrated that the Ni-P-CNT electroless composite coating exhibited higher wear resistance and lower friction coefficient than Ni-P-SiC and Ni-P-graphite composite coatings. After annealing at 673 K for 2 h, the wear resistance of the Ni-P-CNT composite coating was improved. Carbon nanotube/copper matrix composites revealed a lower wear rate and friction coefficient compared with pure copper, and their wear rates and friction coefficients showed a decreasing trend with increasing volume fraction of CNTs within the range from 0 to 12 vol.% due to the effects of the reinforcement and reduced friction of CNTs. The favorable effects of CNTs on the tribological properties are attributed to improved mechanical properties and unique topological structure of the hollow nanotubes.     

化学镀制备高耐蚀耐磨Ni-P-SiC复合镀层

研究了Ni-P-SiC复合镀层的制备工艺和性能以及SiC含量对镀层性能的影响。采用Taber试验机对Ni-P-SiC复合镀层的磨损性能进行了测试,并用VHX-100型三维视频显微镜对磨损形貌进行了观察,分析了复合镀层的磨损机理。结果表明:SiC颗粒的加入能有效地降低摩擦副之间的犁沟效应及摩擦表面发生粘着的面积,从而减少镀层的磨损。采用电化学实验等手段研究了Ni-P-SiC复合镀层的耐蚀性能。当复合镀层均匀一致,能起到一个良好的屏蔽作用时,耐蚀性十分优异;而镀层缺陷的存在将导致耐蚀性能降低。     

配副材料对镍-磷-碳化硅化学复合镀层摩擦磨损性能的影响

利用化学复合镀技术制备了Ni-P-SiC复合镀层,研究了镀层的表面形貌、组织、显微硬度等性能,并对比研究了不同配副材料对Ni-P-SiC复合镀层和Ni-P镀层摩擦磨损性能的影响。结果表明,Ni-P-SiC复合镀层的显微硬度较Ni-P镀层有所提高;与GCr15钢球对磨时,Ni-P-SiC复合镀层发生严重的塑性变形和粘着磨损,但磨损率比Ni-P镀层稍有降低;与Si3N4陶瓷球对磨时,两者的磨损率相当,且均比与GCr15球对磨时小1个数量级,其主要磨损机理为磨粒磨损。配副材料的磨损率变化规律与镀层一致。在一定条件下,陶瓷材料与Ni-P镀层或Ni-P-SiC复合镀层是较匹配的摩擦副。     

Wear-resistant ceramic coatings deposited by liquid thermal spraying

As a surface strengthening and surface modification technology of materials, liquid thermal spray technology has been used in many fields, such as wear and friction reduction, corrosion resistance, and high-temperature oxidation resistance. This article reviews the progress of liquid thermal sprayed coating in wear resistance as well as friction reduction in recent years. The influences of microstructure, composition, phase structure and mechanical properties on the tribological properties of typical coatings (including ceramic coatings and multiphase composite coatings) are investigated. The tribological properties of the coating are determined by the coating characteristics (including microstructure, porosity, mechanical properties, etc.) and the service conditions (working temperature, lubrication state, etc.). Typical ceramic wear-resistant coatings include Al₂O₃, YSZ, HA coatings, etc. The tribological properties of the coating can be significantly improved through process optimization and heat treatment. The comparison of nanostructured and microstructured ceramic-based coating reveals that nanostructured coating reduces wear by absorbing stress. The interaction between different constituent phases improves wear resistance and reduces wear in composite coatings. Finally, various challenges faced by liquid thermal spray are pointed out, and future research focuses are proposed.     

Ni-P-PTFE自润滑镀层的耐磨性能及其增强机理研究

采用化学复合镀技术将纳米聚四氟乙烯(PTFE)微粒沉积到化学镀Ni-P镀层中。扫描电镜(SEM)表明:镀层内PTFE微粒分散均匀,与Ni-P镀层结合紧密。摩擦磨损实验表明:在100N作用下,Ni-P-PTFE镀层的摩擦因数约为0.03,具有良好的摩擦学性能。热处理后的摩擦磨损实验表明:经热处理后,镀层仍具有较低的摩擦因数和良好的耐磨性能。     

TC4合金表面Cu/micro-WC复合镀层和Cu/nano-WC复合镀层的性能

在TC4合金表面分别制备了Cu/micro-WC复合镀层和Cu/nano-WC复合镀层。比较了两种复合镀层的表面形貌、化学成分和显微硬度,同时分析了两种复合镀层的摩擦特性。结果表明:两种复合镀层都由Cu、W、C元素组成,显微硬度都明显低于TC4合金的显微硬度;摩擦试验前后,两种复合镀层表面轮廓曲线的形态都存在明显的不同;与Cu/micro-WC复合镀层相比,Cu/nano-WC复合镀层的表面形貌较好,W元素的质量分数较高,耐磨性较强。