Self-lubricating Composite Coatings Research Articles

Effect of appropriate vibration frequency on microstructure and properties of laser cladding Co-based self-lubricating composite coatings

Effect of appropriate vibration frequency on microstructure and properties of laser cladding Co-based self-lubricating composite coatings

One-step preparation of high performance Ni-MoS2 self-lubricating coatings via jet electrodeposition on additive manufactured aluminum alloy

Composite coatings with solid lubricants can improve the tribological performance of aluminum alloy parts prepared by Laser Powder Bed Fusion (LPBF). In this study, Ni-MoS2 self-lubricating composite coatings were one-step prepared on additive manufactured aluminum alloy surface via jet electrodeposition. The properties and lubrication performance of the coatings prepared using composite electrolyte with different MoS2 particle diameters and concentrations were investigated. The lubrication mechanism of the composite coating was discussed. The results showed that 0.8 μm MoS2 had less agglomeration than 80 nm, resulting in a uniform surface. The lubrication performance of the composite coating was affected by MoS2 particles content and coating hardness. With the increase of MoS2 concentration in the composite electrolyte, the friction coefficient and wear rate decreased, and achieved the best lubrication performance of 0.12 friction coefficient and 0.11 mg/m wear rate when MoS2 composite electrolyte is 5 g/l and MoS2 is 0.8 μm. However, the addition of soft MoS2 decreased the coating hardness, lower hardness will cause lubrication failure.

Effects of nano-h-BN and Ag-coated Cu on the microstructure and friction-reduction properties of self-lubricating composite coatings

High-strength steel (42CrMo) is frequently used to manufacture components under high load and high friction conditions. To improve the surface tribological properties, nickel-based alloy coatings with Ag(Cu)/nanoNi/h-BN nanosheets were prepared on the surface of 42CrMo steel by laser cladding technique. The effects of Ag(Cu) and nanoNi/h-BN on the microstructure evolution, hardness and friction-reduction properties of the cladding layer were discussed. The results show that the coating microstructure changes significantly. The addition of micron Ag(Cu) and nanoscale Ni/h-BN increased the nucleation rate of the melting pool, and the columnar dendritic crystals were transformed into fine cells. The addition of nanoparticles enabled the coating to obtain a higher microhardness of 575.4HV0.2, which is about 1.4 times of the substrate. The mechanical properties of the coating were improved, and the friction coefficient and wear rate were significantly reduced, with good friction-reduction property. The wear mechanism mainly consists of a composite wear of slight adhesive wear, abrasive wear and oxidation wear.

Enhancing high-temperature fretting wear resistance of TC21 titanium alloys by laser cladding self-lubricating composite coatings

Fretting wear is one of the main factors restricting the fastener service reliability for the high-temperature titanium alloys. Enhancing the high-temperature fretting wear resistance of titanium alloys with laser cladding coatings is an effective method. Thus, in this work, a self-lubricating composite coating was designed and fabricated on the surface of TC21 titanium alloy with laser cladding. Special attentions were made to the effect of the fractions of the hard and self-lubricating phases on high-temperature fretting resistance. In addition, the contribution of laser cladding power was also concerned. The primary phases of the self-lubricating composite coatings are α-Co, CaF2, WC, TiC and Cr23C6, and the reasons for the formation of TiC and Cr23C6 are investigated from a thermodynamic point. The prepared composite coatings are dense and uniform. The crystallographic characteristics and the volume fractions of the hard phases (WC, TiC and Cr23C6) and self-lubricating phase (CaF2) were revealed, and the effect of grain size on the coating properties was analyzed. The hardness of the coatings were all maintained around 700 HV0.2, which was significantly higher than that of the substrate. The composite coating significantly improves the friction and wear resistance at 500 ℃. The hard phase was also found to be the most resistant to friction and wear. The frictional performance of the coating gets better when the hard phase and the self-lubricating phase increase. However, the hard phase contributes more to the high-temperature friction and wear resistance than the self-lubricating phase and the wear volume is 1/40 that of substrate. For the laser cladding power, the higher power can lead to a higher fraction of CaF2 but a lower fraction of hard phase, causing a decline in COF but an increase in wear volume. The wear mechanisms of the coating and the substrate were analyzed, the subsurface stress distribution state of the wear scars were further analyzed. The current results present new insights on the anti-wear design strategy to the composite coatings consist of hard and self-lubricating phase.

Synergistic effect of Ag and MoS2 on high-temperature tribology of self-lubricating NiCrBSi composite coatings by laser metal deposition

To increase the performance of the tool materials operating at high temperatures (HT), the protection of the surface from wear is usually needed. Conventional lubricants pose problems due to their degradation and harmful effects on human health; therefore, self-lubricating materials are of great importance. In the current work, self-lubricating NiCrSiB millimeter-thick composite coatings with the addition of solid lubricants Ag and MoS2 were fabricated on stainless steel substrates using laser metal deposition. Upon microstructural analysis, it was revealed that the addition of MoS2 resulted in a uniform distribution of Ag throughout the coating thickness owing to a unique phenomenon of silver encapsulation. Further, the coatings were subjected to sliding wear tests against an alumina counterbody at a load of 5 N, a speed of 0.1 m s−1, and a distance of 500 m under a unidirectional condition in a ball-on-plate configuration. The tests were performed from 20 to 800 °C. The results show that self-lubricating composite coatings demonstrate an exceptional performance up to 800 °C. Significant friction (best at 800 °C ⁓0.25) and wear (best at 600 °C ⁓4.3 times less) reduction for Ag + MoS2 added coating is seen. It was revealed that the presence of CrxSy and Ag on the wear track delivered lubrication at temperatures ≤400 °C while, a glazed tribolayer rich in silver molybdate phase (along with CrxSy, MoO3) was an effective lubricant at 600 and 800 °C. The results are reported in comparison to the unmodified Ni-based alloy.

Effects of WS2 and Cr3C2 addition on microstructural evolution and tribological properties of the self-lubricating wear-resistant CoCrFeNiMo composite coatings prepared by laser cladding

Effects of WS2 and Cr3C2 addition on microstructural evolution and tribological properties of the self-lubricating wear-resistant CoCrFeNiMo composite coatings prepared by laser cladding

Tribological behaviour of HVOF-sprayed Ni-based self-lubricating composite coatings

ABSTRACT In the current investigation, the tribological behaviour of HVOF sprayed Ni-based self-lubricating composite coatings on cast iron substrate, which is a commonly used material for cylinders, was studied. Four different combinations of coatings materials, namely, Ni–10Mo–10Al, Ni–10Mo–10Al–10graphite, Ni–10MoS2–10Al and Ni–10MoS2–10Al–10graphite were deposited on a cast iron substrate. Then, the mechanical, morphological and tribological properties of the coated and uncoated samples were analysed by performing microhardness measurements, a scratch resistance test, a wear test (pin on disc), XRD and SEM/EDS. Results showed that among all coatings, Ni–10MoS2–10Al–10graphite coated cast iron sample has the highest microhardness of about 349.4 HV 111% higher than the substrate material and lowest average wear rate of about 1.1 × 10−4 g s−1.

Wear Mechanism of Fe/Cu Self-Lubricating Composite Coatings Fabricated by Electro-Explosive Spraying under Dry Friction

In the present work, Fe/Cu composite coatings were fabricated by electro-explosive spraying technology (EEST), with good lubrication performance and high wear resistance. The microstructure and morphology were characterized by an energy-dispersive spectrometer (EDS), 3D digital microscope, and scanning electron microscope (SEM) coupled with electron backscattered diffraction (EBSD). Mechanical properties and tribological performance were measured using a micro Vickers hardness tester, universal testing machine, and universal friction and wear testing machine. The composite coating had low porosity with a minimum value of 0.7%, high microhardness with a maximum value of 729.9 HV0.2, high bonding strength with a maximum average value of 55.25 MPa, and good wear resistance and self-lubrication, and the ratio of soft metal and hard metal in the coatings was controllable. Under dry friction conditions, the friction reduction mechanism was that there were both metallic oxide particles and soft metal attached in the friction pairs. When the ratio of soft metal in the composite coating was higher, the self-lubricating performance of the coating was better, with adhesive wear as the main wear mechanism; when the ratio of hard metal was higher, the wear resistance was better and the wear mechanism was mainly abrasive wear.

A comparative study on microstructure and tribological characteristics of Mo2FeB2/WC self-lubricating composite coatings with addition of WS2, MoS2, and h-BN

To enhance the tribological properties and service life of Mo2FeB2/WC coatings, self-lubricating composite coatings with addition of WS2, MoS2, and h-BN were fabricated using laser cladding. The morphology, microstructure, microhardness, and tribological properties of the Mo2FeB2/WC self-lubricating composite coatings were investigated. The results indicated that the addition of WS2, MoS2, and h-BN increased the bonding properties between the coating and substrate. Sulfides and nitrides were found in the self-lubricating composite coatings; the Mo2FeB2/WC/h-BN coating exhibited a fine dendritic structure. The microhardnesses of the Mo2FeB2/WC, Mo2FeB2/WC/WS2, Mo2FeB2/WC/MoS2, and Mo2FeB2/WC/h-BN coatings were 1591.3 HV0.5, 1345.6 HV0.5, 1378.9 HV0.5, and 1415.3 HV0.5, respectively. After the addition of WS2, MoS2, and h-BN, the coefficients of friction decreased by 9.09%, 15.15%, and 30.30%, respectively; the corresponding wear rates decreased by 10.80%, 19.03%, and 30.97%, respectively. The self-lubricating phases significantly improved the tribological properties of the Mo2FeB2/WC coating. The main wear mechanisms of the Mo2FeB2/WC coating were adhesive and mild oxidative wear; the wear mechanisms after the addition of WS2, MoS2, and h-BN were abrasive and oxidative wear. The wear debris was powder-like for the Mo2FeB2/WC/WS2 and Mo2FeB2/WC/MoS2 coatings and flake-like for the Mo2FeB2/WC/h-BN coating. The lubricating transfer film caused an improvement in the tribological properties.

Self-lubricating composite coatings: A review of deposition techniques and material advancement

In recent years, variouscoatings materials have been developed butare incapable of meeting the rising needs for improved power density, longer durability, and more efficiency in futuremechanical systems. As opposed to a large fluid barrier separating the sliding surfaces and preventing direct contact, advanced mechanical assemblies commonly operate in boundary-lubricated sliding regimes in which asperity interactions may occur. In addition, a number of industrial applications need sliding contact without liquid lubrication, exacerbating the issue. Several novel coatings were developed to boost lubricity and durability in tribologically demanding applications. Several of these conventional coatings consist of metal, polymers, polymer-ceramic composites, and metal-matrix composites. self-lubricating composite coatings have proved effective in a variety of technical applications. Self-lubricating composite coatings are those sorts of coatings that are applied to a surface by a specific procedure based on the intended use. These coatings improve the substrate material's microstructure, mechanical, and tribological characteristics. This paper describes the coatingtechnique andself-lubricating composite materials.

Effects of Thermal Treatment on Microstructure and Wear Properties of Ni60/CeO2 Composite Coating 35CrMoV Steel by Laser Cladding

Laser cladding Ni60/2.0 wt.%CeO2 self-lubricating anti-wear composite coatings on 35CrMoV steel were thermally treated at 25 °C, 500 °C, 600 °C and 700 °C for 1 h, respectively. The macroscopic morphology of composite coatings was characterized by optical microscopy. The evolution of microstructure was studied by scanning electron microscopy. The precipitated phase of the coating was analyzed by X-ray diffractometer. The microhardness and wear properties of the composite coatings were measured by microhardness tester and friction and wear test. The effects of thermal treatment and no thermal treatment on the mechanical properties of the composite coatings were systematically studied by the above experiments. The experimental analysis shows that the main phase composition of Ni60/2.0 wt.%CeO2 composite coating is γ-(Ni, Fe), Cr7C3, Cr23C6, CrB, CrFeB and Cr2Ni3. Meanwhile, in XRD, it can be seen that the diffraction peak has shifted to the left and the single diffraction peak is decomposed into double diffraction peaks with the thermal treatment at 700 °C, which indicates that the lattice in the coating phase has a certain distortion. Compared with the coatings without thermal treatment, Ni60 cladding layer has more uniform solute distribution and a denser and more uniform structure after thermal treatment at 700 °C. The laser cladding anti-wear composite coating demonstrates that the wear resistance performance shows the greatest improvement after thermal treatment at 700 °C.

Detonation Self-Lubricating Antifriction Glass Composition

Antifriction self-lubricating glass composite coatings of the Sic-Ni-Cu-Al-Si-C type additionally contain an aluminoborosilicate glass phase and structurally free MgC2, which forms α-graphite during thermolysis, the synergistic effect of which causes modification of the friction surface due to the formation antifriction layer. The influence of the structural components of the coating on their contribution to the antifriction properties is considered. It was clarified that an increase in the adhesive strength of the coatings was achieved by preliminary application of a sublayer of vitreous sodium silicate. The developed coatings showed high performance properties, while the means of minimizing and stabilizing wear characteristics was the presence of a thin-film antifriction layer based on α-graphite, which shields unacceptable processes of molecular-adhesive interaction.

Enhancement of frictional properties of Ni-MoS2 self-lubricating composite coatings by microgroove arrays

The self-lubricating Ni-MoS2 composite coating deposited on a stainless-steel (SS) surface with microgroove arrays are prepared and detailed characterized in this paper. Laser surface texturing (LST) and electrochemical deposition (ECD) are carried out successively to fabricate such composite coating. Compared with the Ni-MoS2 coating deposited directly on the non-LST substrate, the coefficient of friction (COF) of the Ni-MoS2 coating on the microtextured substrate is reduced from 0.17 to 0.14, the wear volume is decreased by 21%, the average depth of wear track is decreased by 61%, the running-in time is significantly minimized to 1/11, and the lifetime is remarkable increased. The excellent frictional properties can be attributed to the influence of the microtexture on the growth pattern of Ni-MoS2 coating, as well as the synergistic lubrication effect between texture and the Ni-MoS2 structure.

Improved tribological performance of epoxy self-lubricating composite coating by BNNSs/Ag

The application of epoxy (EP) self-lubricating composite coatings to the surface of mechanical parts has attracted attention increasingly, since they are beneficial for extending the lifetime of equipment by decreasing friction and wear. However, the shortcoming of poor wear resistance of EP is a limited factor in tribology. In the present study, the hard hexagonal boron nitride nanosheets (BNNSs) supported soft metal of Ag nanoparticles (Ag NPs) was constructed to strengthen the tribological performance of EP. The BNNSs was firstly prepared after h-BN being treated by NaOH/KOH solution, and then Ag NPs were uniformly anchored on the BNNSs surface through hydrothermal method. The achieved BNNSs/Ag surface had rough microstructure and active sites, which were conducive to the interfacial compatibility between BNNSs and EP. The tribological test results demonstrated that the lubricity and wear resistance of EP coating were improved significantly by BNNSs/Ag. Especially as the weight fraction of BNNSs/Ag was 0.7 %, the corresponding composite coating showed an 80.5 % and 86.4 % reduction in the friction coefficient and wear rate compared to EP coating, which was mainly because of the good interfacial interaction in the composite coating, the “hard-soft” synergistic reinforcing and lubricating effect of BNNSs/Ag, as well as self-lubricating property of transfer film. Furthermore, the tribological behaviors of BNNS/Ag/EP composite coating under pure water and oil lubrication were investigated comparatively. The enhancement mechanism of BNNSs/Ag was proposed by analyzing the worn surface of composite coatings and counterparts.

Influence of ceramic coating pores on the Tribological performance of PEO–PTFE composite coatings on the Ta–12W alloy

Self-lubricating composite coatings with an intermeshing structure on the Ta–12W alloy were fabricated using plasma electrolytic oxidation (PEO) and polytetrafluoroethylene (PTFE) impregnation sintering. Porous PEO ceramic coatings were formed in alkaline silicate–phosphate electrolytes using NaF and NaOH as the pore morphology adjustment agents. The tribological performances of the PEO ceramic and PEO–PTFE composite coatings were examined under 10–70-N loadings using a ball-disk wear tester. An optimized basic PEO ceramic coating with a thickness of 25 μm, a porosity of 23.8 %, and a hardness of 1410 HV is obtained in an electrolyte containing 5 g/L of NaF and 5 g/L of NaOH. A soft PTFE lubricating layer is fixed on the hard PEO ceramic coating, forming an intermeshing structure that can effectively reduce the coefficient of friction (COF) over time while enhancing the load capacity of the composite coating. In addition, the synergistic effect of the PEO ceramic coatings and self-lubricating material is proposed. The PTFE material stored in the pores will be constantly transferred to the contact interface to achieve a reduced COF. The PEO ceramic coating with a suitable porous structure acts as an “armor” because it can withstand a large load and provide physical support to the PTFE material during the friction process. Thus, the composite coating achieves a low COF with a low wear rate and a high load-bearing capacity.

A Comparative Study on Microstructure and Tribological Characteristics of Mo2feb2/Wc Self-Lubricating Composite Coatings with Addition of Ws2, Mos2, and H-Bn

A Comparative Study on Microstructure and Tribological Characteristics of Mo2feb2/Wc Self-Lubricating Composite Coatings with Addition of Ws2, Mos2, and H-Bn

Enhancement of Frictional Properties of Ni-Mos2 Self-Lubricating Composite Coatings by Microgroove Arrays

Enhancement of Frictional Properties of Ni-Mos2 Self-Lubricating Composite Coatings by Microgroove Arrays

Role of layered double hydroxide in enhancing wear and corrosion performance of self-lubricating hydrophobic Ni-B composite coatings on aluminium alloy

A layered double hydroxide reinforced nickel boride (LDH/Ni-B) hydrophobic composite coating was deposited on the A356 aluminium alloy surface by the electroless method. The anti-corrosion and anti-wearing performances were studied with varying amounts (0–5 wt%) of LDH in the nickel boride matrix. The composite coating with the highest water contact angle having a value of 120° was observed for Ni-B containing 0.5 wt% of LDH. This could be attributed to the increased surface roughness offered by the LDH layers. Potentiodynamic polarization measurements in 3.5 wt% NaCl solution indicate a significant decrease in the corrosion current density (icorr) values for LDH added composite coating with a lowest of 3.96 × 10−6 A/cm2 for 0.5 wt% of LDH. This may be due to the combined effect of both coating hydrophobicity and feasibility for chloride ion intake by the ion-exchange mechanism of LDH. Improved wear resistance was obtained for composite coated aluminium with a minimum wear rate for 1% LDH added coating. Self-lubricating tribolayer formation in the presence of LDH gave higher wear resistance.

Microstructure and tribological properties of Co-Ti3SiC2 self-lubricating composite coatings on 304 stainless steel by laser cladding

采用激光熔覆同步送粉法在304不锈钢上制备出自润滑耐磨涂层，熔覆粉末配比为纯Co，Co-2% Ti3SiC2（质量分数，下同）和Co-8% Ti3SiC2。借助扫描电子显微镜（SEM），能谱分析仪（EDS）和X射线衍射仪（XRD）对熔覆涂层进行表征，系统地研究304不锈钢与涂层在室温和600℃下的摩擦学性能与磨损机理。结果表明：激光熔覆Co-Ti3SiC2涂层的平均显微硬度高于基体（240.3HV0.5），N1，N2和N3涂层的硬度分别为285.7HV0.5，356.3HV0.5和463.8HV0.5，涂层主要由连续基体γ-Co固溶体，硬质相Fe2C，Cr7C3和TiC，润滑相Ti3SiC2组成。在室温下，基体和N1，N2，N3涂层的摩擦因数分别为0.56，0.62，0.68和0.42，N1，N2，N3三种涂层的磨损率分别为9.15×10-5，7.81×10-5，4.66×10-5 mm3/（N·m），均明显低于基体（66.42×10-5 mm3/（N·m））；在高温下，基体和N1，N2，N3涂层的摩擦因数为0.66，0.54，0.52和0.46，N1，N2，N3三种涂层磨损率分别为37.79×10-5，35.6×10-5，18.83×10-5 mm3/（N·m），均低于基体（41.3×10-5 mm3/（N·m））。在室温和600℃下，涂层具有高于304不锈钢基体的显微硬度，且Co-8% Ti3SiC2涂层呈现出最好的自润滑耐磨性能。

Development and characterization of Co-Cu/Ti3SiC2 self-lubricating wear resistant composite coatings on Ti6Al4V alloy by laser cladding

The poor tribological property of Ti6Al4V strictly limits its application as high-speed moving parts, so three coatings (pure Co, Co-Ti 3 SiC 2 , and Co-Cu/Ti 3 SiC 2 ) were fabricated on the Ti6Al4V by laser cladding to improve the wear-resistant properties. The phase, microstructure, microhardness , and wear morphology of the coatings were characterized to investigate their performance. At room temperature, due to the good synergistic effect between Cu and Ti 3 SiC 2 , Co-Cu/Ti 3 SiC 2 coating had good tribological performance that the friction coefficient and wear rate was 0.146 and 1.76 × 10 −7 mm 3 /N·m, respectively. This paper deeply explores the effects of Ti 3 SiC 2 and Cu in the coatings which will provide theoretical basis for enriching the laser cladding material system, and also provides a technical reference for the commercial application of Ti6Al4V. • The Co-Cu/ Ti 3 SiC 2 coating was successfully prepared on Ti6Al4V alloy by laser cladding. • The MAX phase Ti 3 SiC 2 and soft metal Cu simultaneously played lubricating role in the coatings. • The wear mechanisms of Co-Cu/Ti 3 SiC 2 composite coating have also been deeply studied.