Mechanical and tribological properties of nanocomposite TiSiN coatings

TiSiN coatings with a thickness of 2.5 μm were deposited using a Large Area Filtered Arc Deposition (LAFAD) technique with TiSi targets having different Si content. The influence of the Si content in the coatings on the mechanical properties and tribological behaviors of the TiSiN coatings were systematically studied using nanoindentation and a pin-on-disk tribometer. Nanoindentation results show that the hardness and Young's modulus of the TiSiN coatings increase with increasing Si content in the coatings. Wear test results indicate that the wear rate and friction coefficient of the 440a stainless steel coupons were significantly reduced by deposition of the TiSiN coatings, and the tribological behaviors of the TiSiN coatings are strongly dependent on the Si content in the coatings and the testing ball material. TiSiN coatings exhibit similar friction coefficient when tested against Al₂O₃ and 302 stainless steel balls, but increasing Si content in the coatings causes an increase in the friction coefficient of the TiSiN coatings. With the increase in the Si content in the coatings, the wear rate of the TiSiN coatings decreases when tested against Al₂O₃ balls, but increases significantly when tested against 302 stainless steel balls. The capability of forming a transfer layer on the ball surface contributes to the change in the friction coefficient and wear rate with Si content in the coating and ball materials.     

Electrodeposition and properties of Zn–Ni–CNT composite coatings

Zn–Ni–CNT composite coatings were prepared by electrodeposition from a sulphate bath. The effect of CNTs on the corrosion behavior, wear resistance and hardness of the composite coatings was investigated. Their corrosion properties were evaluated by polarization, impedance, weight loss and salt spray tests. The CNT particles inclusion improved the corrosion resistance, hardness and wear resistance of the coating. The grain size of the composite coating was smaller than that of a pure Zn–Ni coating with the same Zn/Ni ratio. Scanning electron microscope images and X-ray diffraction patterns of coating revealed its fine-grain nature.     

Characterisations of low phosphorus electroless Ni and composite electroless Ni-P-SiC coatings on A356 aluminium alloy

A low phosphorus electroless nickel coating of Ni-2.5?wt-%P alloy and a composite coating of Ni-5?wt-%P-SiC were prepared on A356 aluminium alloy substrates using two types of electroless bath solutions, an alkaline bath for low phosphorus and acidic for composite plating. The coatings morphologies have been characterised using optical and scanning electron microscopy. In addition, X-ray diffraction, microhardness, reciprocating wear testing and adhesion tests have been conducted to characterise structure and mechanical properties of the resulting coatings. The results obtained revealed that a crack-free and homogeneous coating could be produced using an optimum bath formulation. The maximum thickness of the composite coatings was 50?µm, the thickness of coatings tested. The composite coating was more resistant to wear in comparison to the low phosphorus nickel one, but had lower adhesion.     

Mechanical properties of a hybrid cemented carbide composite

Microstructural effects on the mechanical properties of a hybrid metal matrix composite, double cemented (DC) carbide, have been investigated. DC carbide contains granules of WC/Co cemented carbide in a matrix of cobalt. Overall composite hardness increases with decreased granule cobalt content as well as with decreased intergranular matrix fraction of cobalt. High-stress abrasive wear resistance also increases with decreased granule cobalt content and matrix fraction. Fracture toughness of the composite increases with increased cobalt matrix fraction and to a lesser extent with increased granule cobalt content. Increased granule size increases both fracture toughness and wear resistance. DC carbide exhibits a superior combination of fracture toughness and high-stress wear resistance than conventional cemented carbide. The combination of toughness and wear resistance in the composite improves with increased granule hardness.     

Mechanical properties of tungsten fiber reinforced ZrAlNiCuSi metallic glass matrix composite

Tungsten fiber reinforced (Zr₅₅Al₁₀Ni₅Cu₃₀)_98.5Si_1.5 metallic glass composites were fabricated and characterized. The mechanical properties of the composite under compression and tension were investigated. Tungsten reinforcement greatly increased compressive strain to failure compared to the unreinforced (Zr₅₅Al₁₀Ni₅Cu₃₀)_98.5Si_1.5 metallic glass. The compressive failure mode changed from a single shear band to multiple shear bands and to localized fiber buckling and tilting as the volume fraction of tungsten fiber increased. The maximum tensile strength and strain to failure of each of the composites were lower than those of unreinforced material due to the lack of substantial shear bands. Tensile toughness changed to some extent due to different interface reactions. The reason for the improved mechanical properties is discussed.     

Mechanical and tribological properties of multi-element (AlCrTaTiZr)N coatings

Multi-element (AlCrTaTiZr)N coatings are deposited onto Si and cemented carbide substrates by reactive RF magnetron sputtering in an Ar + N₂ mixture. The influence of substrate bias voltage, ranging from 0 to − 200 V, on the microstructural, mechanical and tribological properties of these nitride coatings is studied. A reduction in concentration of N and Al is observed with increasing substrate biases. The (AlCrTaTiZr)N coatings show the face-centered-cubic crystal structure (B1-NaCl type). The use of substrate bias changes the microstructure of the (AlCrTaTiZr)N coating from the columns with microvoids in boundaries to the dense and less identified columns. The compressive macrostress increases from − 0.9 GPa to − 3.6 GPa with an increase of substrate bias. The hardness and adhesion increase to peak values of 36.9 GPa and 60.7 N at the bias voltage of − 150 V, respectively. The tribological properties of the (AlCrTaTiZr)N coatings against 100Cr6 steel balls are evaluated by a ball-on-disc tribometer with a 10 N applied load. With an increase of substrate bias, the wear rate reduces while the friction coefficient almost keeps constant at 0.75. The lowest wear rate of 3.65 × 10^− 6 mm³/Nm is obtained for the (AlCrTaTiZr)N coating deposited at the bias voltage of − 150 V.     

等离子喷涂法制备铁基硬质涂层的力学性能

为了在碳钢表面制备耐磨涂层,使涂层与基体的膨胀系数相近,减少涂层应力,将80％ Fe,13％P,7％C(质量分数,％)机械混合粉末进行等离子喷涂,制备铁基耐磨涂层.采用粘结剂对偶试样拉伸试验法测定涂层结合强度,采用表面显微硬度法分析涂层硬度,采用MMW-2型(高温)摩擦磨损试验机以40Cr硬质合金为对磨材料对涂层进行耐磨性试验.结果表明,涂层的结合强度平均值为29.16 MPa,显微硬度的平均值为7.889 MPa,高于陶瓷涂层硬度值,涂层的耐磨性能较好,磨损200 min后,涂层的磨损量在36 mg左右,磨损量约为对磨件的1/13,涂层磨损主要为磨粒磨损机制.     

氧化铝含量对Ni-P化学复合镀层摩擦学性能的影响

采用化学镀技术制备了不同氧化铝含量的Ni-P复合镀层,并用球盘式磨损试验机测试了镀层的摩擦磨损性能。利用扫描电镜、光学显微镜和X射线衍射仪对镀层和对偶球的表面形貌、成分及微观结构进行了表征,分析了镀层的磨损机理。结果表明：镀层中氧化铝质量分数最高可达34.7%,但镀层磷含量显著降低,Ni-P合金基体为无定形结构;镀层的摩擦因数(约为0.49～0.58)高于Ni-P合金,且随着氧化铝含量的增加先降低后增加,镀层的维氏硬度从502上升至764,磨损率从1.2×10_-14 m₃/(Nm)单调下降至3.2×10_-15 m₃/(Nm),镀层的主要磨损机理由粘着磨损逐步转变为磨粒磨损。     

Study on the characteristics of Ni-W-P composite coatings containing nano-SiO2 and nano-CeO2 particles

The aim of this research work was to co-deposit nano-SiO₂ and nano-CeO₂ particles into the Ni-W-P alloy coating in order to improve the surface properties further. Ni-W-P-SiO₂-CeO₂ composite coatings were prepared by co-deposition of nickel, tungsten, phosphorus, nano-SiO₂ and nano-CeO₂ particles on the surface of 15 steel from the electroplating bath which nano-SiO₂ and nano-CeO₂ particles were suspended by high speed mechanical stirring. The characteristics of the composite coatings were assessed by micro hardness test, Taber Abrader test, scanning electron microscopy and X-ray diffraction. The results obtained in this study indicate that the nano-SiO₂ and nano-CeO₂ particles were dispersed evenly within the Ni-W-P alloy coating and the bonding between the matrix metal and nano-SiO₂ and nano-CeO₂ particles is compact. That the co-deposition of nickel, tungsten, phosphorus, nano-SiO₂ and nano-CeO₂ particles leads to uniform Ni-W-P-SiO₂-CeO₂ composite coatings possessing better micro hardness and abrasion resistance properties when heat-treated at 400 °C for 3 h. In addition, that nano-CeO₂ and nano-SiO₂ particles can increase the thermal stability of Ni-W-P alloy coating at high temperature.     

石墨烯颗粒对Ni-Co-石墨烯复合镀层的表面性能影响

为了得到性能更加优异全面的复合镀层,使用复合电沉积技术制备不同石墨烯颗粒大小的Ni-Co-石墨烯复合镀层,并制备了Ni-Co合金镀层。测试镀层的表面形貌,相结构,显微硬度,耐磨性和耐蚀性能。结果显示,石墨烯在电沉积中很好的嵌入到了镀层基质中,而且石墨烯的存在并没有改变镀层基质的晶体结构;石墨烯的填加增加了复合镀层的显微硬度,最高可达805HV;降低了复合镀层的摩擦系数,在一定程度上减少了粘着磨损的面积;复合镀层的自腐蚀电流密度可以降低到1.0905×10-5A/cm2,低于Ni-Co合金镀层的自腐蚀电流密度。说明了石墨烯的添加增强了复合镀层的硬度,耐磨性和耐蚀性。     

Recycled hard metal-base wear-resistant composite coatings

The abrasion-erosion wear resistance of composite coatings from self-fluxing Ni-base alloy and WC-Co hard metal powders is evaluated. The resistance of thermal sprayed and melted NiCrSiB-(WC-Co) coatings was found to be markedly higher than that of NiCrSiB and slightly higher than that of comparative welded coatings. Microstructural and surface analyses were used to describe the coatings and the wear damage. Based on the principles of creating wear-resistant coatings and on experimental studies of wear resistance, high wear-resistant, composite NiCrSiB-(WC-Co) coatings were fabricated. These coatings exhibited 300% higher wear resistance than 0.45% C steel.     

Characterization of the mechanical properties and failure modes of hard coatings deposited by RF magnetron sputtering

Chromium oxide coatings with thicknesses of several micrometers were deposited by RF magnetron sputtering at various oxygen flow rates and sputter powers on carbon steel and high speed steel (HSS) substrates, respectively. The compositions and structures of the coatings were characterized by EDS, XRD, and XPS. The mechanical properties of the coatings, in terms of hardness and reduced elastic modulus, were determined by nanoindentation technique. UMT was used to carry out scratch test to study the coating failure mode. Correlations between the mechanical properties of the coating and substrates and the coating failure mode are discussed, which reveal that the coating with a low thickness and high hardness underwent plastic deformation during the scratch process, while the thicker coating with a lower hardness failed in chipping or spallation. The substrate plays a more important role than the coating itself in determining the coating failure mode.     

碳纳米管复合镀层在不同摩擦组合下的摩擦学行为

对CVD法制备的碳纳米管进行了表面改性和修饰,然后通过化学共沉积方法制备了高硬度的碳纳米管复合镀层,并研究了碳纳米管复合镀层在不同摩擦组合下的摩擦学行为.结果表明:经过改性处理后的碳纳米管表面拥有丰富的表面官能团,这使大量的碳纳米管复合于镀层中,从而导致了镍磷复合镀层的硬度显著提高,达到946 HV.摩擦实验得出,在润滑状态下以钢环为摩擦副,碳纳米管增强的镍磷复合镀层比传统耐磨材料SiC增强的镍磷复合镀层具有更低的摩擦系数和磨损率.此外,不同摩擦组合下的摩擦结果表明,SiC复合镀层相互摩擦时尽管拥有较低的磨损率,但其摩擦系数仍然较高,而碳纳米管复合镀层相互摩擦时表现出最低的摩擦系数和磨损率,其摩擦系数和磨损率分别为0.108 7和1.49×10-3 g/m.     

Friction and wear behavior of Cu-CeO2 nanocomposite coatings synthesized by pulsed electrodeposition

The friction and wear behavior of copper matrix nanocomposites reinforced with nanosized ceria particles, synthesized by pulse electrocodeposition technique, have been investigated. Tests have been carried out under dry sliding conditions by rubbing against a steel ball at varying loads ranging from 4 to 20 N and at constant speed of 11 rpm using a ball-on-disk wear tester. The experimental results indicate that the wear resistance of copper composite is superior to that of pure copper at all the loads and it improves with the increasing amount of ceria in the copper matrix. The friction coefficient and wear rates increase with the increase in applied load. When the load increases from 4 to 20 N, the transition of wear regime from local damage to delamination of a mechanically mixed layer (MML) occurs.     

TEM analysis and tribological properties of Plasma Electrolytic Oxidation (PEO) coatings on a magnesium engine AJ62 alloy

In order to reduce the fuel consumption and pollution, automotive companies are developing magnesium-intensive components. However, due to the low wear resistance of the magnesium (Mg) alloys, Mg cylinder bores are vulnerable to the sliding wear attack. In this paper, a Plasma Electrolytic Oxidation (PEO) process was used to produce oxide coatings on a Mg alloy AJ62 (MgAl6Mn0.34Sr2), developed for Mg engine block, to battle against the wear attack. The surface morphology, coating thickness and tribological properties were tailored by adjusting the PEO process parameters. TEM analysis demonstrated that the PEO coatings had a nanocrystalline structure in the inner dense layer next to the substrate. The PEO coatings exhibited a much better wear resistance and a smaller friction coefficient than the uncoated AJ62 substrate. The tribological performance of the PEO-coated Mg alloy was even better than that of a hypereutectic Al-Si alloy currently used for engine applications under a high contact load.     

The effects of pulse-reverse parameters on the properties of Ni-carbon nanotubes composite coatings

A nickel based composite coatings reinforced with carbon nanotubes (CNTs) were prepared by pulse-reverse electrodeposition. The effects of reverse ratio and frequency on the surface morphology, micro-hardness and corrosion resistance of Ni-CNTs composite coatings were studied. The results showed that higher pulse reverse ratio and pulse frequency made the surface morphology of the coatings more homogeneous. The micro-hardness of the coatings increased with the increase of reverse pulse ratio but decreased with the increase of pulse frequency. Corrosion resistance of the coatings first increases then decreases as the pulse frequency and reverse ratio increase. The best corrosion resistance was obtained for coatings under the condition of 30% reverse ratio and 100 Hz pulse frequency. The effects of CNTs on the properties of the composite coatings were discussed.     

Wear-resistant WC composite hard coatings by brazing

A wear-resistant tungsten carbide/copper (WC/Cu) brazing alloy coating was deposited onto a steel substrate by high-temperature furnace brazing. Compared with other hard surfacing processes, much larger WC particles could be used to make a metal layer with higher wear resistance. ASTM G-65 wear test results for the brazed composite coating showed a higher wear resistance when compared with some WC-Co hard coatings that are commonly used. In this paper, the brazing alloy, the brazing process, and the after-brazing heat treatment are studied. The microstructure of the brazing alloy and the as-deposited coating were characterized, and no significant porosity was found. A good metallurgical bond was formed at the WC/Cu alloy interface and at the composite coating/substrate interface. Little or no dilution was observed. The bond strength between the Cu alloy and substrate is also much higher than for a thermal spray coating. This paper was presented at the 2nd International Surface Engineering Congress sponsored by ASM International, on September 15–17, 2003, in Indianapolis, Indiana, and appeared on pp. 592-96.     

Microstructure and wear properties of aluminum/aluminum-silicon composite coatings prepared by cold spraying

Composite coatings containing aluminum and aluminum-11.6 wt.% silicon eutectic alloy phases of varying compositions were fabricated using cold spraying. Coating contained a uniform distribution of the two phases. The hardness of the coatings increased as the volume fraction of Al-Si in the coating increased. The length to width ratio of the splats was found to be larger for Al particles compared to Al-Si particles. Dry sliding ball-on-plate wear tests indicated that the wear volume loss was similar for the Al and Al/Al-Si composite coatings in spite of the increase in microhardness. This discrepancy is explained by the inter-splat delamination mechanism. The coefficient of friction of aluminum coating reduced on Al-Si addition.     

电沉积制备Ni/nano-WC复合镀层的工艺及机理研究

采用脉冲电沉积法制备了纳米WC强化镍基复合镀层。探究了不同表面活性剂（十二烷基硫酸钠）添加量以及WC粉的湿磨预处理对Ni/nano-WC复合镀层表面形貌、颗粒分布、微观结构以及显微硬度的影响。表面活性剂的添加和对WC湿磨处理有助于细化镀层晶粒,得到WC颗粒分布均匀的致密镀层。镀层中WC含量以及镀层的显微硬度随着表面活性剂的添加量的增加而增加,但过量会使效果变差,理想的SDS添加量为0.15g/l,湿磨10h。     

A review of the electrodeposition of metal matrix composite coatings by inclusion of particles in a metal layer: an established and diversifying technology

Following a brief overview of their history, which dates back to the 1920s with marked developments during the 1960s and 1970s, the principles of composite coatings, achieved by including particles dispersed in a bath into a growing electrodeposited metal layer, are considered. The principles and role of electroplating compared to other techniques for realising such coatings, are considered. A good quality particle dispersion (often aided by a suitable type and concentration of surfactants) appropriate choice of work-piece shape/geometry and controlled agitation in the bath are seen to be prerequisites for achieving uniform coatings having a well-dispersed particle content by electroplating. Examples are provided to illustrate the influence of bath composition and plating conditions on deposit properties. Engineering applications of included particle composite layers are illustrated by examples of hard ceramic, soft ceramic and polymer inclusion composite coatings from the recent literature. Current trends in the development of composite plated coatings are summarised and their diverse applications are seen to include the use of finely structured (especially nanostructured) and functionally active particles together with hybrid and more complex, e.g. hierarchical, structures for applications ranging from tribology to speciality electronics, magnetic and electrochemical energy conversion materials.