Friction Coefficient Of Coatings Research Articles

Microstructure and Wear Performance of High-Velocity Arc Sprayed FeMnCrNiBNbAl Coating

In this study, FeMnCrNiBNbAl wear-resistant coatings were prepared via high-velocity arc spraying technology on the surface of Q235 steel. The effects of spraying distance, voltage, and current on the coating performance were studied via the orthogonal experimental method with microhardness and porosity as evaluation indicators, and the process parameters were optimized. The order of primary and secondary factors affecting coating performance were: spraying distance, voltage, and current. The optimized process parameters are: spraying distance 200 mm, voltage 36 V, and current 240 A. The coating prepared using the optimized process parameters has an average microhardness of 756 HV0.1 and an average porosity of 1.03%. The coating mainly consists of α-Fe, Fe-Cr, Ni-Cr-Fe, Al2O3, and (Fe, Ni) solid solution. The coating friction coefficient was 0.5 while that of the substrate was 0.7. The depth and width of the wear marks of the coating were 6.32 µm and 555.41 µm, respectively, which are 66% and 32% lower in comparison with Q235 steel under the same test conditions. The wear forms of this coating were mainly fatigue peeling and adhesive wear.

High-Temperature Heat Treatment of Plasma Sprayed Ti–Si–C–Mo Coatings

In this work, the effect of 800 °C and 1100 °C post-heat treatment on the plasma spraying of Ti–Si–C–xMo (x = 1.0, 1.5) composite coatings was investigated. The composite coatings were composed of TiC, Ti3SiC2, Ti5Si3 and Mo5Si3 reacted phases. After heat treatment, the Ti3SiC2 and Mo5Si3 phases increased. The coating microhardness decreased by 16% and 18% for Ti–Si–C–1.0Mo and Ti–Si–C–1.5Mo coatings, respectively, after heat treatment at 1100 °C. Fracture toughness increased by 16% for the Ti–Si–C–1.5Mo coating after heat treatment at 1100 °C, which was mainly due to the heat treatment promoting Ti3SiC2 formation, healing micro-cracks, reducing the internal stress and making the microstructure dense. The coating friction coefficient before and after heat -treatment was between 0.4 and 0.6. After heat treatment, the wear amount of the coating was first reduced and then increased, and the minimum wear loss occurred after heat treatment at 800 °C. The wear mechanism was mixed abrasive wear, adhesive wear and tribo-oxidation wear.

Structure and tribological properties of detonation coatings based on Cr3C2-NiCr after pulse-plasmaine treatment

Cr3C2-NiCr metal-ceramic coatings have found wide application in the protection of machine parts and equipment operating under extreme conditions. In this study, Cr3C2-NiCr based detonation coatings which have been subjected to pulse-plasma treatment were studied. The study showed that IPO reduced the surface roughness by 48 %, reduced the coating friction coefficient by about 2 times, increased the hardness of the coatings from the original 12 GPa to 16.2 GPa and improved their wear resistance by 2 times compared to untreated coatings. Pulse-plasma treatment provides qualitative formation of coatings from metal-ceramic material of Cr3C2-NiCr system with complex heterogeneous structure-phase state, where the layered structure of areas of carbide particles and matrix metal in immediate proximity from “carbide-matrix” border with selections in matrix of dispersed secondary carbides is revealed.

New evaluation method for the characterization of coatings by electroerosive alloying

The running-in coatings were formed on the surface of tin bronze QSn10-1 by electroerosive alloying (EEA) with soft antifriction materials such as silver, copper, Babbitt B83 and graphene oxide (GO). The mass transfer, surface roughness, coating thickness and dry friction coefficient of the running-in coatings were measured and analyzed by a precision electronic balance, three-dimensional optical profiler, metallographic microscope, scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and friction and wear tester. An evaluation indicator system for the characterization was constructed based on six factors, including material price, time, mass transfer, roughness, thickness and friction coefficient of the coatings by electroerosive alloying. The Shannon entropy method was used to calculate the weight of different indices, and a comprehensive evaluation method for running-in coatings performance was proposed by combining the technique for order preference by similarity to ideal solution (TOPSIS) and a multicriteria decision-making technique. The TOPSIS model was employed for the comprehensive evaluation ranking of the characterization of the running-in coatings by electroerosive alloying.

Structure and properties Ag—C coatings sprayed by electrical explosion on copper substrate

In the presented article it was studied the structure and the properties of the C-Ag coating electrical explosion sprayed on copper substrate. It was found that obtained coating, from 7...200 µm thick, has complex relief. Graphite is represented as plate shape structures and sub-nanosized globular particles. There are also copper oxide particles in the coating. A transition area with a thickness of 100...150 nm, which has a complex structure, is formed on the boundary between the coating and the substrate. The silver grains in the coating have a platelet structure, and the copper substrate has a subgrain structure. The hardness and Young's modulus of the "coating (Ag-C)/(copper) substrate" system increase with the distance from the surface to the boundary between the coating and the substrate. The coating wear parameter is 2.3 times less compared to the copper substrate. The coating friction coefficient is equal to the substrate friction coefficient.

Fabrication and characterization of graphene oxide reinforced Ni[sbnd]B composite coating by pulsed electrodeposition technique

The present study reports some properties of Ni-B-GO composite coatings deposited on the surface of St37 steel (low carbon steel) substrate by pulse electrodeposition technique. The graphene oxide (GO) was utilized as reinforcement in the bath. The mechanical properties of NiB coating and Ni-B-GO composite coatings showed that while the indentation depth was high for the NiB coating, the indentation depth decreases with the increase in GO content. The friction coefficient of coatings decreases from 0.46 to 0.28 as GO amount increases. The result of wear test reveals that an amount of 100 mg GO in the coating layer provide a relatively smooth wear track. GO behaves as a lubricate during friction and wear test between the test sample and counter-face and decreases the friction coefficient. It was found that the dominant wear mechanism is adhesive wear. The corrosion potential of composite coating was decreased depending on the GO content. The icorr value of the NiB coating was 1.9 × 10−5 A·cm−2 while this value reduces to 2.6 × 10−6 A·cm−2 for GO-100 sample. The Ecorr value of the NiB coating was −0.565 mV, while the GO particles included in the coating, the Ecorr value increases to −0.470 mV.

Упрочнение FeCrMoWCBSi аморфных электроискровых покрытий карбидом вольфрама

A new direction in the development of metal-matrix coatings are composites based on an amorphous matrix with reinforcing ceramic additives. In this work, composite coatings were prepared by electrospark treatment of AISI 1045 in a mixture of iron granules with a multicomponent composition CrMoWCBSi and the addition of tungsten carbide powder. According to X-ray analysis, with an increase in the concentration of WC in the mixture of granules up to 1.2 vol.%, the content of the WC phase in the coating composition increased. In addition, the X-ray analysis showed metallic tungsten, which is a product of the partial dissolution of WC particles in the iron melt. In the microstructure of the coatings, inclusions of tungsten carbide with a diameter of 1.8 ± 0.9 μm were observed. The oxidation resistance of the coatings at a temperature of 700°C decreased monotonically with an increase of WC additive in the mixture of granules. The microhardness of the coatings with tungsten carbide was in the range from 814 to 1118 HV, which is higher compared to a completely amorphous sample (743 HV). The average values of the coating friction coefficient with WC ranged from 0.60 to 0.67, which is 30 % lower than that of an amorphous coating. The wear rate of coatings with tungsten carbide was in the range of 0.5 –1.1×10−5 mm3 / Nm, which is lower than that of the sample without WC (1.8 ×10−5 mm3 / Nm). The optimal value of the addition of WC powder in the mixture of granules during the deposition of the coatings for tribotechnical applications is 1.2 vol.%. Thus, the use of amorphous coatings reinforced with tungsten carbide makes it possible to reduce the wear of steel 45 by up to 8 times.

Influence of Graphene on Microstructure and Corrosion and Wear Resistance of Micro-Arc Oxidation Coatings on D16T Al Alloy Drill Pipe

Coatings were prepared on D16T Al alloy in electrolytes with and without graphene by micro-arc oxidation technology. Influences of graphene on the microstructure, corrosion and wear resistance of the coating were investigated. X-ray diffraction analysis result indicates that the coating is mainly composed of α-Al2O3, γ-Al2O3 and Al substrate. γ-Al2O3 was the dominant phase. The microstructure of coatings characterized by scanning electron microscopy, energy-dispersive x-ray spectroscopy and transmission electron microscopy shows the coating with graphene is flatter, denser, less pores and cracks than that of the coating without graphene. Moreover, the coating is consistent of a loose outer layer and dense inner layer. A little molten particles and many agglomerates accumulated on the surface of the coating. Graphene successfully embedded into the coating remarkedly decreased micro-pores and micro-cracks and slightly increased the thickness. The coating with graphene shows the better corrosion and wear resistance than the coating without graphene. The current potential, corrosion current density, wear and friction coefficient of coatings with graphene were − 0.41 V, 3.97E−8 A/cm2, 1.57 mg and 0.68, respectively, revealing the desirable corrosion and wear resistance. The presence of graphene in coatings improved the thickness and microstructure and increased the corrosion and wear resistance of the coating.

Semi-convertible Hydrogel Enabled Photoresponsive Lubrication

Summary A semi-convertible hydrogel with reversible photoresponsive supramolecular lubricating ability is demonstrated by integrating a responsive supramolecular system of α-cyclodextrins/polyethylene glycol (α-CD/PEG) and competitive guest 1-[p-(phenylazo)benzyl]pyridinium bromide (AzoPB) within a poly(vinyl alcohol) (PVA) and polyacrylamide (PAAm) framework. The competitive host-guest interaction between α-CD/PEG supramolecular network and AzoPB after UV and visible-light irradiation enables the appearance and disappearance of the sol-state layer on the hydrogel surface while the PVA and PAAm consistently keeps the framework. This semi-convertible process realizes the reversible photoresponsive lubricating ability and variable toughness. We envision that this finding will offer a possible way for fabricating novel smart devices far beyond lubrication, leading to an emerging branch of interdisciplinary materials science that integrates supramolecular chemistry, hydrogel, and surface science.

Effect of Ni60-WC on Properties of NiCrAl Coating

Ni60-WC reinforced NiCrAl coatings were prepared on the TC4 alloy by laser cladding technique with different mixed powders: 95%NiCrAl-5%Ni60-WC, 85%NiCrAl-15%Ni60-WC, 75%NiCrAl-25%Ni60-WC (wt.%). The microstructure, phases compositions, microhardness, wear properties were studied. The results showed that the mainly consists of dendrites and bulk like compounds crystal and some of flower-like microstructure formed. The XRD results indicated TiC, VC metalloceramics, Cr0.2Ti0.8C, NiTi2, Ni2W4C and AlFe3C intermetallic compounds generated. The microhardness of the coatings are 881HV0.3, 778HV0.3 and 788HV0.3, respectively. Compared with the substrate hardness about 200HV0.3, the hardness of coatings have been improved significant. The friction coefficient of coatings are 0.35, 0.42, and 0.42, respectively, and the wear rates of the coatings are 3.86×10-7mm3N-1m-1, 4.51×10-7mm3N-1m-1 and 4.34×10-7mm3N-1m-1, respectively.

Tribological performance and behaviour of CVD TiC/TiCN/TiN multilayer coating at elevated temperature

ABSTRACT TiC/TiCN/TiN multilayer coating was prepared on a high-speed tool steel W6Mo5Cr4V2 by chemical vapour deposition. The tribological performance and behaviour of the coating were investigated at an elevated temperature of 400–600°C. Results show that the friction coefficient of the coating first decreases from 0.39 to 0.08 and then increases from 0.08 to 0.23 with the increase in temperature, while the average wear rate increases continuously from 0.97 × 10−13 to 2.11 × 10−13 m3N−1m−1. The tribochemical product of Fe2O3 in the tribo-oxidative layer (TiO2 + Fe2O3) could reduce the coating friction coefficient but enlarge the wear rate. As the Fe2O3 component increases, the consumption of the tribo-oxidative layer accelerates gradually and the coating wear mechanism transforms from the mild oxidative–abrasive–adhesive wear to severe oxidative–adhesive wear.

Structure and Properties of Coatings in the Cr–B–C–N System Obtained Using a CrB2 Cathode by the Method of Pulsed Cathode-Arc Evaporation P-CAE in Ar, N2, and C2H4 Media

The technology of pulsed cathode-arc evaporation (P-CAE) has been successfully applied for coating deposition in the Cr–B–C–N system. The coatings had a structure typical for arc coatings with a significant fraction of the condensed droplet phase, but the formation of an adverse columnar morphology has been eliminated. The coatings contained crystallites of the h-CrB2 and с-CrN phases along with a large amount of the amorphous phase, the composition of which varied depending on the type of the working environment. The coatings obtained in argon demonstrated the highest hardness of 12 GPa, while those obtained in the C2H4 medium were characterized by the highest elastic-plastic properties (elastic recovery 72%). The friction coefficient of coatings deposited in Ar, N2, and C2H4 media was 0.7, 0.4, and 0.3, respectively. The phase of diamond-like carbon in the latter case resulted in a decrease in the friction coefficient due to high fraction of sp2-bonded carbon serving as a dry lubricant. The coatings of the optimal composition were resistant to high temperature oxidation in the temperature range 600–1000°С. At high temperatures, the oxidation process was followed by intensive diffusion of boron atoms in depth of the substrate.

Development of the chemical vapor deposition process for applying molybdenum coatings on the components in assembly and engine construction

The process of chemical vapor deposition of Mo and Mo-С coatings was studied by means of thermal decomposition of molybdenum hexacarbonyl. The kinetics of the coating growth in the range of 480 °C–540 °C and the pressure in the reaction volume from 9 Pa to 16 Pa were explored. The dependences of coating growth rate, the magnitudes of their microhardness on the parameters of their obtaining, as well as the changes in the morphology of the coating surface, roughness, and structure, were established. The tribological properties of the obtained coatings coupled with bronze Br.Su3H3S20F0.2 were explored at the friction machine 2070 SMT-1 according to the cube–roller scheme in a load interval of 0.2–1.4 kN. The lubrication during determining the friction coefficients was carried out by immersion of the movable counter body into a bath with fuel TC-1, GOST 10227-86. It was necessary to conduct such research because there is insufficient information when it comes to the specific equipment and peculiarities of the object onto which a coating is applied. When developing the process of coating application on specific components, techniques, and means to ensure the uniformity of parts heating and precursor feeding to their surface were tested. As a result of the conducted studies, we obtained the regions of parameters of obtaining coatings with different structure, rate, hardness, as well as the patterns of changes in these characteristics at the change of the basic parameters of the process of obtaining such coatings. Depending on application conditions, coatings may have hardness from ~11,000 MPa to 18,000 MPa at a growth rate from 50 μm/h to 170 μm/h. The mean values of the friction coefficient of coatings with different microstructure and microhardness were 0.101 at the load of 0.2 kN and 0.077 at the load of 1.4 kN. Based on the conducted research, it was possible to develop the process of applying the metal and metal-carbide molybdenum-based CVD coatings in regards to the components of the assembly and engine construction, which can serve as the basis for the development of industrial technologies

Preparation and vacuum tribological properties of composite coatings fabricated by effective introduction of soft metal Ag into spray-formed YSZ templates

The friction coefficient of thermal sprayed ceramic coatings is relatively high, and the traditional introduction of lubricants will result in the decline of mechanical properties of coatings, which severely limits their applications. Herein, YSZ/Ag self-lubricating coatings were prepared on 316 L stainless steel substrates via thermal spraying technology, vacuum impregnation and in-situ synthesis for the first time. The morphologies, mechanical properties and vacuum tribological performance of composite coatings were studied in detail by comparing with YSZ coatings. Results show that silver particles distribute in the pores, cracks of YSZ coatings, and the filling of defects by silver improves the micro-hardness, fracture toughness and cohesive strength of the coatings. In addition, owing to the formation of lubricating film during the sliding process in vacuum, the friction coefficient of the coating is reduced by about 2 times and the wear rate is reduced by about 600 times after the introduction of silver. At the same time, the addition of the silver lubricant makes the wear of the coupling ball significantly reduced. Since the lubricating film can be continuously replenished and repaired, the YSZ/Ag self-lubricating coating has a relatively long service life (>100,000 sliding cycles).

Influence of Y2O3 on the microstructure and tribological properties of Ti-based wear-resistant laser-clad layers on TC4 alloy

Multi-track Ti-based wear-resistant composite coatings were fabricated on TC4 alloy surfaces using laser-clad TC4 + Ni45 + Co–WC mixed powders with different Y2O3 contents (0, 1, and 3 wt%). The microstructure, microhardness, and tribological properties of the coatings were characterised using X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, electron probe X-ray micro analyser, microhardness tester, and friction and wear testing apparatus. The results showed that the number of cracks on the coating surfaces gradually decreased with the addition of Y2O3 and that residual Co–WC powders existed in the coating subsurfaces. The phase composition of the coatings with different Y2O3 contents remained unchanged and was mainly composed of reinforcing phases of TiC, TiB2, Ti2Ni, and matrix α-Ti. With the addition of Y2O3, the coating microstructure was remarkably refined, the direction characteristic of the TiC dendrites obviously weakened, and the nucleation rate significantly increased. When the added Y2O3 was 3 wt%, a large amount of TiB2–TiC-dependent growth composite phases precipitated in the coating. The two-dimensional lattice misfit between (0001)TiB2 and (111)TiC was 0.912%, which indicated that TiB2 and TiC formed a coherent interface. When the amount of Y2O3 was increased, the microhardness of the coatings gradually decreased, and the wear volume of the coatings first increased and then decreased. Under the effect of the TiB2–TiC composite phases, the wear resistance of the 3 wt% Y2O3 coating was optimal. The 3 wt% Y2O3 coating friction coefficient was the lowest, and the wear mechanism was abrasive wear.

Effect of heat treatment on microstructure and tribology behaviour of electroless Ni-P/BN(h) composite coating

ABSTRACTSub-micron (0.1–0.3 µm) BN(h) particles were incorporated into Ni-P plating coatings to enhance their mechanical and tribological properties. The morphology, phases and elemental analysis of Ni-P/BN(h) coatings were characterised by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Energy Dispersive Spectroscopy (EDS) and 3D surface profiler, respectively. The tribological properties of Ni-P/BN(h) coatings annealed at different temperatures (200–600°C) were investigated to determine the optimal annealing temperature to enhance their wear resistance as well as to reveal the underlying mechanisms. The results illustrated that co-deposited BN(h) particles can lower friction coefficient and enhance wear resistance. Increasing the annealing temperature, the micro-hardness of the annealed coatings gradually decreased from 1008 HV0.1 (400°C) to 848 HV0.1 (600°C) as a result of the Hall-Petch effect, nevertheless these values were higher than that of the as-deposited coating (692 HV0.1). With regard to the tribological property, the Ni-P coating presented a poorer wear resistance (6.7 × 10−5 mm3 N−1 m−1) in comparison with the Ni-P/BN(h) coating (3.1 × 10−5 mm3 N−1 m−1). In addition, coatings annealed at different temperatures ranging between 200∼600°C exhibited improved wear resistance (2.7 × 10−5–7.2 × 10−6 mm3 N−1 m−1) attributable to their higher hardness, the self-lubricating nature of BN(h) and the lubrication effect of oxides arising from the tribochemical reaction between Ni3P and the environment. Overall, the Ni-P/BN(h) coating annealed at 400°C for 1 h lowers the coating friction coefficient by about 58% and the wear resistance of the Ni-P composite is about 10 times higher than Ni-P coating.

Deposition of Amorphous Hardening Coatings by Electrospark Treatment in a Mixture of Crystalline Granules

This article is devoted to the formation of amorphous coatings on the steel 35 surface by electrospark treatment in a mixture of crystalline granules. It is revealed by the energy dispersive X-ray spectroscopy (EDS) that formed coatings contain W, Mo, Co, and Ni in various ratios. The weight of granules of various compositions decreases by 11–16 wt % for 6-h treatment due to electric erosion. The mass transfer coefficient varies in a range from 33 to 54%. X-ray structural analysis showed the prevalence of an amorphous phase (81–99%) in the structure of deposited layers. Annealing of coatings at a temperature above 1150°C leads to the crystallization of the amorphous phase into boron carbide of the M23(C, B)6 type, as well as into α-Fe. The coatings have an increased hardness of 10–15 GPa, while their wear resistance in the dry sliding wear mode under loads of 10 and 50 N is higher than for steel 35 by a factor of 3.3 and 1.6. The coating friction coefficient is lower than for steel 35 by 13–30% and was 0.27–0.31. The wear resistance of coatings in a dry abrasive wear mode is higher by a factor of 3–5 when compared with uncoated steel 35. The best characteristics are inherent without nickel and worst are inherent without cobalt. Thus, it is established that tungsten and cobalt increase the wear resistance of iron-based amorphous alloys, while nickel and molybdenum tend to worsen their tribotechnical behavior.

Flexible and thermally stable superhydrophobic surface with excellent anti-corrosion behavior

Superhydrophobic films with excellent flexibility, mechanical robust and thermally stable properties have been fabricated through a facile one-step spray-coating process based on bisphenol A based benzoxazine (BA-a), polyurethane (PU) prepolymer, and mesoporous SiO2 (SBA-15). The curing mechanism between BA-a and PU prepolymer morphologies, water contact angles and thermal stability of coatings were characterized and discussed. In addition, the corrosion behavior of the superhydrophobic coatings on the tin plate was characterized by the polarization curve and electrochemical impedance spectroscopy. The coatings made by different weight ratios of BA-a to PU can maintain a contact angle higher than 150°; meanwhile, the coatings had a micro-nano structure with a Tg more than 221 °C. The coatings can be bent by the finger which illustrates their excellent flexible properties. Furthermore, friction coefficient of coatings can reach 1.70. The electrochemical corrosion test results indicated that the superhydrophobic coatings possessed excellent corrosion resistance (Icorr can reach 8.90 × 10−5 A cm−2 with certain ratio), which could have a potential at harsh environment.

Wear behavior of AlCrSiVN coatings at elevated temperature up to 700 °C

AlCrSiVN coatings were deposited on cemented carbides substrates by a hybrid configuration of high-power impulse magnetron sputtering (HiPIMS) and cathode-arc-evaporation. The effect of varying V content on microstructure, hardness, and wear resistance of AlCrSiVN at RT–700 °C was investigated. Indentation hardness of AlCrSiVN coating decreases from 34.0 ± 1.1 to 26.3 ± 2.4 GPa with increasing V content from 0 to 7.5 at.%. However, elastic modulus of coating changes slightly. In addition, adhesion strength of AlCrSiVN to cemented carbide substrates first increases and then declines as the V addition content is increased. At RT, all friction coefficients of coatings are nearly the same, independent of V addition content. AlCrSiVN coating with 7.5 at.% V possesses the lowest wear rate at RT–600 °C. Lubricative V2O5 oxide scale forms on coating surface at 600 °C, providing self-lubrication during high-temperature wear. This favors to produce reduction of both friction coefficient and wear rate at 600 °C. At RT–600 °C, abrasive wear is responsible for the wear of AlCrSiVN coatings. However, the decrease of oxidation resistance induced by V addition produces a serious oxidation wear of coating at 700 °C.

Microstructure and friction coefficient of ceramic (TiC, TiN and B4C) reinforced Ni-based coating by laser cladding

Ni204 ceramic composite coatings with different mass fractions of TiC, TiN and B4C were successfully prepared on the surface of 45 steel by laser cladding. Microstructures of different ceramic coatings were studied using X-ray diffraction, scanning electron microscopy and laser confocal microscopy. The friction coefficient and microhardness of ceramic coatings were measured with a reciprocating friction wear machine and microhardness tester. The results show that ceramic coating has 766.8HV0.5 average microhardness and friction coefficient of 0.47 when 10%TiC, TiN, and B4C are added to initial powder Ni204. The microstructure of cladding layer is uniform and compact, and the microhardness and friction coefficient of the coating increased and decreased by factors 2.6 and 1.393 compared with initial powder. This is due to the presence of multiple phase ((Ti, Mo, Nb) (C, B, N)), carbide, nitride, (Ti, Mo, Nb) (C, B, N), and (Ti, Mo, Nb) (C, N) ring phase around TiC, TiN, and Ti(C, N) ceramic phases. Uniformly distributed reinforced phases in the coating inhibit extrusion by grinding balls on the surface of the ceramic coating, thus changing original abrasive wear mechanism, making wear marks more shallow, and decreasing friction coefficient of the surface.