Wear Performance and Mechanisms of Polyphenylene Sulfide/Polytetrafluoroethylene Wax Composite Coatings Reinforced by Graphene

Polyphenylene sulfide (PPS) composite coatings reinforced by graphene were prepared through a spraying method. Wear performance of the composite coatings were evaluated using a block-on-ring test rig, and the results showed that the wear life of the composite coatings were over seven times higher than that of a pure PPS coating. Wear mechanisms of PPS composite coatings reinforced by graphene are discussed. It was concluded that adhesive wear was the major wear mechanism of the pure PPS coating but the wear form of the composite coatings was dominated by abrasive wear due to the graphene filler that has high mechanical strength. In addition, fatigue wear appeared for composite coatings with higher content of graphene. The formation of a uniform thin transfer film on the counterpart ring and fine wear debris for the composites coatings during abrasion were consistent with the improvement of wear performance. The 3D morphology of the surface of the counterpart ring was also used to discuss the wear mechanism of PPS composite coatings.     

Abrasive resistance of arc sprayed carbonitride alloying self-shielded coatings

Wear-resistant coatings were prepared on the surface of the Q235 low-carbon steel plate by HVAS with the carbonitride alloying self-shielded flux-cored wire. Detection and analysis on the microstructure and properties of the coatings were carried out by using scanning electron microscope, microhardness tester and wear tester. The forming, the wear resistance and its mechanism of the coatings were studied. The results show that the coatings have good forming, homogeneous microstructure and compact structure. The coatings have good hardness, the average microhardness value reaches 520 HV_0.1, and the highest value is up to about 560 HV_0.1. As a result, the coatings have good abrasive wear performance and adhesion strength.     

A brief review on the wear mechanisms and interfaces of carbon based materials

Abstract

The demand for reducing wear and friction has become the chief aim in the automotive industry nowadays. The usage of lubricant is not considered enough as there is still room for improvements. As a solution, much research has arisen towards what we called self-lubricating ideas, in order to reduce friction better than lubricant. This paper presents an overview wear mechanism and the interface of carbon-based materials. This paper will also discuss the interfaces by carbon as substrate and coating layer. The findings show that for metals, the predominant wear mechanisms were abrasion and fatigue. Meanwhile, for polymers and coating (DLC), they were abrasive along with adhesive wear. The surface roughness of the substrate plays a crucial role in increasing the excellent performance of the DLC coating. The interfaces of carbon elements definitely give huge impact on both self-lubricant materials and coatings where the coefficient of friction and wear rate changes drastically even with 1 wt.% addition. Nevertheless, a clear understanding of the factors that affect the tribological performance is very essential in performance improvement for potential applications.     

碳纳米管增强镍磷基复合镀层研究

对CVD方法制备的碳纳米管进行表面改性处理，然后在液相中分散，利用化学共沉积方法形成碳纳米管镍磷基复合镀层，研究了碳纳米管表面改性后的红外谱、碳纳米管复合镀层的表面形貌、硬度及摩擦学行为.结果表明：碳纳米管的加入明显地提高镍磷复合镀层的硬度和改善了镍磷复合镀层的摩擦性能.硬度达到946HV，20N载荷时摩擦系数为0.7，增至80N时降为0.6；相同条件下与传统耐磨材料SiC增强的镍磷基复合镀层相比，具有更低的摩擦系数和磨损量. 关键词： 碳纳米管 表面改性 复合镀层 摩擦行为     

Friction and wear properties of the co-deposited Ni-SiC nanocomposite coating

Ni-SiC nanocomposite coatings were produced by electrodeposition from a nickel sulfate bath containing SiC nanoparticles with an average particle size of 30 nm. The characteristics of the coatings were assessed by scanning electron microscopy and microhardness test. The friction and wear performance of Ni-SiC nanocomposite coatings and Ni film were comparatively investigated sliding against Si₃N₄ ceramic balls under non-lubricated conditions. The results indicated that compared to Ni film, Ni-SiC nanocomposite coating exhibited enhanced microhardness and wear resistance. The effect of SiC nanoparticles on the friction and wear resistance is discussed in detail.     

SiC-Based Composite Materials Obtained by Siliconizing Carbon Matrices

We have developed a method for fabrication of parts of complicated configuration from composite materials based on SiC ceramics, which employs the interaction of silicon melt with the carbon matrix having a certain composition and porosity. For elevating the operating temperatures of ceramic components, we have developed a method for depositing protective silicon-carbide coatings that is based on the interaction of the silicon melt and vapor with carbon obtained during thermal splitting of hydrocarbon molecules. The new structural ceramics are characterized by higher operating temperatures; chemical stability; mechanical strength; thermal shock, wear and radiation resistance; and parameters stability.     

激光熔覆原位合成Nb(C,N)陶瓷颗粒增强铁基金属涂层

采用预涂粉末激光熔覆技术,在42CrMo基体上制备出原位合成Nb(C, N)颗粒增强的铁基复合涂层。X射线及扫描电镜分析结果表明:激光熔覆获得的涂层基体为耐氧化、耐蚀性良好的Fe-Cr细晶组织及少量的-Fe相,原位合成的Nb（C, N）呈块状弥散分布在基体上。进一步的磨损试验表明:这些颗粒增强相极大增强了抗磨损性能,与未熔覆的母材相比,其磨损失重仅为母材的1/9左右; 涂层在750 ℃恒温氧化条件下具有较好的抗氧化性能,氧化层主要由NbO1.1,Cr2O3相组成; 母材的氧化产物为Fe2O3,容易脱落,保护性能较差; 激光熔覆涂层的氧化膜厚度仅为未涂层的1/5。     

Deposition of silicon–carbon coatings from the plasma of a non-self-sustained arc discharge with a heated cathode

Amorphous hydrogenated carbon doped with silicon oxide (a-C:H:Si:O), which is referred to as silicon–carbon coatings in this work, consists of thin amorphous films, which are used as commercial solid lubricants due to their higher stability under extreme environmental conditions as compared to amorphous hydrogenated carbon. The deposition of silicon–carbon coatings from the plasma of a non-self-sustained arc discharge with a heated cathode is considered. Silicon–carbon coatings are deposited using polyphenul methylsiloxane as a precursor at a flow rate of 0.05 mL/min in an argon atmosphere at a pressure of 0.1 Pa. A high-frequency power supply is used to apply a high-frequency bias voltage to a substrate during deposition. After deposition, the mechanical properties of the coatings are studied. The maximum hardness of the coating is 20 GPa at a minimum friction coefficient of 0.16 and a wear rate of 1.3 × 10^–5 mm³ N^–1 m^–1. Energy dispersive analysis shows that the coatings contain a significant content of carbon and oxygen (about 80 and 15%, respectively) and a low content of silicon (about 5%).     

Ti6Al4V合金表面激光沉积复合涂层的组织和性能

为了增强Ti6Al4V钛合金的耐磨性,采用激光沉积制造方法在其表面上制备了以原位生成的TiC颗粒和直接添加的WC颗粒为增强相的耐磨涂层,观察了各涂层的微观组织,并测量了涂层的显微硬度和涂层在室温大气条件下的摩擦磨损性能。结果表明各涂层和基体呈现冶金结合,原位自生的TiC和部分熔化的WC颗粒均能够均匀弥散分布于基体上,由于增强相颗粒的弥散强化及激光沉积组织的细晶强化作用,基材的硬度和耐磨性均得到了提高。原位自生的TiC涂层比WC涂层硬度梯度分布平缓,但耐磨性稍差。     

Reciprocating sliding wear behavior of laser-clad small amplitude Mo2Ni3Si/NiSi metal silicide composite coatings

Mo₂Ni₃Si/NiSi metal silicide composite coatings with a fine microstructure consisting of Mo₂Ni₃Si primary dendrites and the interdendritic Mo₂Ni₃Si/NiSi eutectics were fabricated on austenitic stainless steel AISI 321 by laser cladding process. Small amplitude reciprocating sliding wear resistance of the coatings is evaluated as functions of normal load and slip amplitude and the wear mechanisms were discussed based on worn surface morphology observations. Results showed that the Mo₂Ni₃Si/NiSi coatings have excellent small amplitude reciprocating sliding wear resistance.     

Laser surface modification (LSM) of thermally-sprayed Diamalloy 2002 coating

Thermally-sprayed Diamalloy 2002 is widely used as overlay coating in several applications for their good wear and corrosion protection. Although, in the past, any effort has been produced to deposit Diamalloy 2002 with a low degree of defectiveness, some residual porosity and cracks can often affect the final property of the resulting coatings. Different techniques are commonly used to improve the performance of Diamalloy 2002. Recently, laser post-treatment seems to be one of the most promising, being an effective, non-contact, mini-invasive technology.In this respect, the present investigation deals with the application of a continuous wave high power diode laser to post-treat Diamalloy 2002 deposited by HVOF on AA 6082 T6 aluminum alloy. Different laser power and scan speed were investigated in order to identify the process window most favorable to improve the overall mechanical property of Diamalloy 2002 coatings. The changes in morphology, micro-structure and chemical composition of the coatings after laser post-treatments were investigated by inductive gage profilometry and combined SEM-EDXS. Further, the changes in the mechanical properties of the coatings were investigated in terms of hardness, elastic modulus, scratch and wear resistance. Consistent improvements in mechanical property can be achieved by Diamalloy 2002 when laser processing is performed at higher power and reduced scan speed. Yet, too much increase in power density should be always avoided as it can be detrimental to the final property of the coatings and cause high defectiveness and their failure.     

Study on the laser treatment of electroless Ni-P-SiC composite coatings

Effect of the laser treatment on electroless Ni-P-SiC composite coatings was investigated. The microscopic structure, surface morphology, ingredient, and performance of the Ni-P-SiC composite coatings were synthetically analyzed by the use of X-ray diffraction apparatus, scanning electron microscope, energy distribution spectrometer, micro-hardness tester, wear tester and so on. It was found that the composite coatings did make crystalloblastic transformation after laser heating. Structural analysis confirmed that some new types of phase Ni2Si or Ni3Si compound would emerge in the Ni-P-SiC coatings after laser treatment. The micro-hardness measurement results showed that when the laser power was 450 W with scanning speed of 0.5 m/min, the hardness of the coating was superior to the coating obtained by the conventional furnace heating, and wear resistance of the composite coating after laser treating could also improve.     

不同基底石墨烯涂层的层间滑移减磨性能研究

石墨烯薄膜作为一种二维材料,是提高微/纳机电系统(MEMS/NEMS)摩擦力学性能的优异润滑剂.为了探究基底材料和石墨烯层数对其减磨性能的影响,本文通过在不同基底制备了不同层数的石墨烯涂层,利用原子力显微镜(AFM)实验和分子动力学(MD)仿真结合的方法,研究了石墨烯层数对减磨效应的影响.并且通过建立不同层数石墨烯涂层的摩擦性能分析模型,探究出石墨烯层间滑移是产生减磨的主要因素.结果表明:在不同载荷下,石墨烯涂层对硅基底和铜基底均有优异的减磨效果,摩擦力随着石墨烯层数的增加逐渐降低,当石墨烯层数大于10层时,达到最优99.3%的减磨效果.通过仿真分析发现,随着层数增加,石墨烯与基底的干摩擦转变为石墨烯的层间摩擦,并产生层间剪切滑移,石墨烯层间滑移是导致多层石墨烯优异减磨性能的主要因素.     

Plasma transferred arc boriding of a low carbon steel: microstructure and wear properties

Borided coatings on AISI 1018 steel with different boron contents were produced using plasma transferred arc (PTA) melting. The thickness of the coatings ranged from 1 to 1.5 mm and their hardness from 400 to 1600 HV. Hypoeutectic or hypereutectic compositions consisting of primary ferrite or primary Fe₂B borides, respectively, and a eutectic constituent of -Fe+Fe₂B were obtained. The presence of FeB attested in coatings with the highest boron contents seems to be responsible for the intergranular cracks extending from the surface of the coatings to the substrate. Crack free coatings corresponding to the minimum quantity of eutectic and with a minor quantity of FeB were subjected to pin on disk wear testing and compared to the steel of the substrate. It was found that the wear rate of the borided coatings was about four orders of magnitude lower than the wear rate of the steel substrate. A transition from mild to severe wear was observed for the steel substrate material, but it was absent in the case of the borided coatings for the entire range of the applied loads examined. It is shown that the transition in the case of steel occurs when grooving and plastic deformation is replaced by intense cracking of the material above a critical load. In the case of the borided layer the dominant wear mechanism is delamination of the eutectic, however, the platelike borides are able to support the load and remain in the mild wear range for all the loads tested. Both borided and plain steel surfaces have the same friction coefficient after a short transition period, because both develop an oxide layer leading roughly to the same tribosystem with the alumina counterbody.     

镍过渡层对磁控溅射银自润滑涂层性能的影响

研究了镍(Ni)过渡层对镍基合金718基底上沉积的银自润滑涂层性能的影响.实验结果显示,具有过渡层的银涂层晶粒尺寸变小,晶格参数和晶格应变无明显变化,涂层表面更加致密,缺陷减少.在77～300K热冲击50次后,涂层表面无裂纹、剥落等现象,具有良好的抗热震性能.在常温大气、常温真空和?100°C真空三种下,对涂层的摩擦磨...     

Electrochemical deposition and tribological behaviour of Ni and Ni-Co metal matrix composites with SiC nano-particles

Metal matrix composites reinforced with nano-sized particles have attracted scientific and technological interest due to the enhanced properties exhibited by these coatings. Ni-SiC composites have gained widespread application for the protection of friction parts in the automobile industry. The influence of variables like SiC content, current density and stirring speed on microhardness of nano-composite coatings has been studied. The improved microhardness was associated with the reduction in crystallite size determined by X-ray diffraction studies. The influence of incorporation of nano-SiC in hardened Ni-Co alloy matrix was also studied. It was observed that for 28 wt.% Co content in the matrix the microhardness was higher compared to 70 wt.% for a given nano-SiC content. This was associated to the crystal phase of Ni-28Co-SiC being fcc compared to hcp phase exhibited by Ni-70Co-SiC. The wear resistance of pure Ni, Co and nano-composite coatings was studied using pin-on-disc wear tester under dry sliding condition. The volumetric wear loss indicated that, the wear resistance of Ni-SiC nano-composite is better than that of pure nickel deposit. The wear resistance of Ni-Co composites was observed to be superior to Ni composite. The wear behaviour of Ni and Ni-28Co composite was in accordance with the Archard's law. However, the superior wear characteristic exhibited by Ni-70Co-SiC composite followed the reverse Archard's behaviour.     

The effect of carbon nanotubes on the corrosion and tribological behavior of electroless Ni-P-CNT composite coating

In this study, Ni-P-CNT composite coating was successfully deposited on the surface of copper by electroless plating. X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) were used to characterize the coatings. The wear behavior of the coatings was investigated using a pin-on-disk test rig and subsequently friction coefficient data were reported. The corrosion behavior of the Ni-P and Ni-P-CNT coated specimen were evaluated through polarization curves and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl aqueous solution at the room temperature. The results indicated that the incorporation of carbon nanotubes (CNTs) in the coating improved both tribological behavior and corrosion resistance. These improvements have been attributed to superior mechanical properties, unique topological structure and high chemical stability of nanotubes.     

(Ti,Al,Si,C)N nanocomposite coatings synthesized by plasma-enhanced magnetron sputtering

Materials’ surface service property could be enhanced by transition metal nitride hard coatings due to their high hardness, wear and high temperature oxidation resistance, but the higher friction coefficient (0.4-0.9) of which aroused terrible abrasion. In this work, quinternary (Ti,Al,Si,C)N hard coating 3-4 μm was synthesized at 300 °C using plasma enhanced magnetron sputtering system. It was found that the coating's columnar crystals structure was restrained obviously with the increase of C content and a non-columnar crystals growth mode was indicated at the C content of 33.5 at.%. Both the XRD and TEM showed that the (Ti,Al,Si,C)N hard coatings had unique nanocomposite structures composed of nanocrystalline and amorphous nc-(Ti,Al)(C,N)/nc-AlN/a-Si₃N₄/a-Si/a-C. However, the coatings were still super hard with the highest hardness of 41 GPa in spite of the carbon incorporation. That a-C could facilitate the graphitization process during the friction process which could improve the coating's tribological performance. Therefore, that nanocomposite (Ti,Al,Si,C)N coatings with higher hardness (>36 GPa) and a lower friction coefficient (<0.2) could be synthesized and enhance the tribological performance and surface properties profoundly.     

Effects of WC-Co reinforced Ni-based alloy by laser melting deposition: Wear resistance and corrosion resistance

WC-Co reinforced C276 alloy composite coatings are fabricated on Q235 steel by laser melting deposition.The microstructure,hardness,wear performance,and electrochemical corrosion behavior of composite coating are studied.The results show that WC-Co particles are mostly uniformly distributed in the coating and provide favorable conditions for heterogeneous nucleation.The microstructure of C276/WC-Co composite coatings is composed of γ-Ni solid solution dendrites and MoNi solid solution eutectics.The WC-Co particles can effectively improve the hardness and wear resistance of C276 alloy.The average hardness of the composite coating containing 10-wt% WC-Co(447 HV_0.2) are 1.26 times higher than that of the C276 alloy(356 HV_0.2).The wear rate of composite coating containing 10-wt% WC-Co(6.95 ×10^-3 mg/m) is just 3.5% of that of C276 coating(196.23 × 10^-3 mg/m).However,comparing with Hastelloy C276,the corrosion resistance of C276/WC-Co composite coating decreases.     

碳化钨对激光熔覆高熵合金的影响

为了获得高性能的涂层材料,采用激光熔覆的方法,在Q235钢基体上制备了FeSiCrCoMo高熵合金涂层,并研究了WC对高熵合金涂层的组织和性能的影响。通过金相、X射线衍射、扫描电镜、硬度计、磨损试验机分别研究了添加WC前后涂层的微观形貌、相结构、硬度及磨损性能。结果表明:高熵合金FeSiCrCoMo涂层组织为粗大枝状晶,主要由BCC相和金属间化合物构成,添加WC后,涂层中形成了致密细小的胞状晶,同时BCC相增多,金属间化合物明显减少;添加WC后涂层的硬度明显增强,平均硬度提升了23%,涂层表面平均硬度达到了687HV0.2;WC的添加使得涂层的摩擦系数减小,磨损率减小,耐磨性能提高。