Tribological Properties Of Coatings Research Articles

Hard and wear resistant VB2 coatings deposited by pulsed DC magnetron sputtering

Vanadium boride (VB2) coatings have been less concerned, although they have advantages of super-hardness as well as self-lubrication. In this study, VB2 coatings were deposited by pulsed DC magnetron sputtering, and the effect of deposition parameters on the microstructure, mechanical and tribological properties of coatings were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nano- and micro-indentation, and ball-on-disk tribometer. Under the growth condition with high adatom mobility, the coatings exhibited complete (001) orientation and dense texture. A nanocomposite structure that nanocolumns were separated by a secondary phase was especially observed in the coating deposited at 773 K. Both hardness and intrinsic stress of the coatings were improved substantially by increasing the substrate bias or the pulse frequency. The coating deposited at −30 V and 250 kHz, had the hardness of ∼43.6 GPa and the compressive stress of ∼2.0 GPa. Under the load of 2 N, the friction coefficients were ∼0.7 against Al2O3 counterpart, and the wear rates were in the range of 7 × 10−16–8 × 10−16 m3/N m. Under the load of 5 N, the coatings with low intrinsic stress showed better wear resistance, with the wear rate of 10−16 m3/N m.

Mechanical and Tribological Properties of TiTaBN Graded-Composite Coatings Deposited Using the CFUBMS Technique

ABSTRACTIn this study, TiTaBN graded-composite coatings were deposited utilizing different process parameters on D2 steel and glass substrates using pulsed DC closed-field unbalanced magnetron sputtering (CFUBMS). The morphology and structure of the coatings were analyzed using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The hardness and critical load values of the coatings were determined using a microhardness tester and scratch tester, respectively. The tribological properties of the coatings were analyzed in different testing environments using a pin-on-disc tribometer. The properties of the coatings were found to be strongly affected by the coating parameters. The maximum thickness and hardness were obtained at the lowest nitrogen flow rate and highest frequency. Critical load values of coatings were increased with increased nitrogen flow rate. The low nitrogen flow rate and high frequency across the coatings resulted in enhanced tribological properties.

Properties of TiAlN coating deposited by MPIIID on TiN substrates

Metal plasma immersion ion implantation and deposition (MPIIID) is employed to produce TiAlN hard coatings on Ti substrate. To improve the load-bearing capacity of Ti substrate, nitrogen PIII is used to prepare a bearing TiN layer on Ti-base substrate. The MPIIID process is performed using Ti50:Al50 target for different nitrogen/argon gas fractions. The effect of N2/Ar gas ratio on the microstructure, mechanical and tribological properties of TiAlN coatings has been studied. The plastic microhardness of TiAlN increases with increasing the nitrogen gas fraction to reach a maximum value of 30 GPa at 100 % N2. The plasticity index and the resistance to plastic deformation increase with increasing the nitrogen gas fraction. The wear volume loss of TiAlN coating deposited on TiN substrate decreases by a factor of 103 in comparison with pure Ti. Moreover, the friction coefficient decreases from nearly 0.8 for Ti to 0.25 for TiAlN coatings. The enhanced mechanical and tribological properties of the coating are correlated with the formation of TiAlN hard phase. This phase has random-oriented microstructure, finer grain size, high oxidation resistance and residual internal stress. Moreover, the TiN interface acts as a barrier for the motion of dislocations.

The effect of nanocarbides of refractory metals on the tribological properties of coatings of laser welding

The results of metallographic study of coatings of metal powder materials with additives of nanocarbides of tungsten and tantalum obtained by fiber laser cladding are presented. It is shown that, in abrasive wear tests according to the Brinell–Haworth method, wear resistance increases by 4–6 times compared with 34KHN1MA steel, in the case of an increase of nanocarbide content from 10 to 40% of mixture volume.

Investigation of the Si–B–C–N coatings deposited by magnetron sputtering of SiBC targets

Amorphous Si–B–C–(N) coatings are fabricated by magnetron sputtering of sintered Si–B–C targets. The coating structure is investigated using X-ray diffraction, scanning and transmission electron microscopy, scanning probe microscopy, glow-discharge optical emission spectroscopy, and Raman spectroscopy. Mechanical and tribological properties of coatings are determined using nanoindentation, scratch testing, and pin-on-disc testing. The oxidation resistance of coatings is investigated in a temperature range of 1200–1600°C. It is established that coatings of the optimal composition possess hardness of 20 GPa, elasticity modulus of 210 GPa, elastic recovery of 53%, friction coefficient of 0.6 against cemented carbide ball, and oxidation resistance above 1200°C due to the formation of the SiO2-based protective film on their surface. Coatings deposited by sputtering the target of the Si70B25C composition in Ar + 15%N2 medium showed oxidation resistance both under long-term heating at t = 1200°C for 12 h and short-term heating at temperatures of 1400, 1500, and 1600°C.

Al2O3–ZrO2 nanostructured coatings using DC plasma electrolytic oxidation to improve tribological properties of Al substrates

Alumina–zirconia nanostructured coatings were formed on 7075 Al alloy through Plasma Electrolytic Oxidation (PEO) operated in aDC potentiostatic mode. The composite coatings were produced in the range of 425–500V in an alkaline electrolyte containing 4g/LK2ZrF6. Tribological properties of coatings were investigated using dry sliding wear test against WC balls with a pin-on-disc tribometer. Wear rates were evaluated using optical profilometer. It was shown that the nanostructured alumina–zirconia composite coatings can be formed at voltages ≥450V. The coating thickness and roughness were in the range of 15.2–24.2μm and 0.68–2.35μm, respectively. The distribution of Al, Zr and O in the coatings was uniform. Increasing the PEO voltage led to porosity increment and formation of the high temperature tetragonal zirconia phase (t-ZrO2). Significant enhancement in tribological properties for coated samples was achieved: under optimum conditions, corresponding to the PEO treatment at 500V for 200s, the coating wear rate of 2.62×10−6mm3N−1m−1 and friction coefficient of 0.22 were recorded that are about 120 and 3 times lower than those for the substrate.

Investigation of the Si–B–C–N Thin Coatings Deposited Using Magnetron Sputtering of SiBC Targets

Amorphous thin-film Si–B–C–(N) coatings are fabricated by magnetron sputtering of sintered Si–B–C targets. The coating structure is investigated using X-ray phase analysis, scanning and transmission electron microscopy, scanning probe microscopy, glow-discharge optical emission spectroscopy, and Raman spectroscopy. Mechanical and tribological properties of coatings are determined using nanoindentation, scratch testing, and pin-on-disc testing. The oxidation resistance of coatings is investigated in a temperature range of 1200–1600 °C. It is established that coatings of the optimal composition possess hardness of 20 GPa, elasticity modulus of 210 GPa, elastic recovery of 53 %, friction coefficient of 0,6 against cemented carbide ball, and oxidation resistance above 1200 °C due to the formation of the SiO2-based protective film on their surface. Coatings deposited by sputtering the target of the Si70B25C composition in Ar + 15%N2 medium showed oxidation resistance both under long-term heating at t = 1200 °C for 12 h and short-term heating at temperatures of 1400, 1500, and 1600 °C.

Adhesion and tribological properties of TiTaBN coatings with a graded interlayer deposited by pulsed DC biased and continuous dc biased magnetron sputtering

The properties of TiBN-based coatings are significantly affected by adding alloying elements and coating parameters. Therefore, in this study, TiTaBN coatings with graded interlayer (CWGIL) were deposited on D2 steel substrates by pulsed DC biased (PDCB) and continuously DC biased (CDCB) closed field unbalanced magnetron sputtering (CFUBMS). The structural, mechanical, adhesion and tribological properties of the coatings were analysed with EDS, SEM, XRD, microhardness, scratch testing and a pin-on-disc tribo-tester (under various atmospheric conditions). TiTaBN CWGIL deposited by PDCB magnetron sputtering (MS) had a very dense microstructure, high hardness and a high critical load value. TiTaBN CWGIL deposited by PDCB MS had a lower friction coefficient, the wear rate and the penetration depth in all atmospheric conditions. In conclusion, the application of a PDCB substrate instead of a CDCB one dramatically increases the performance of CFUBMS-deposited TiTaBN coatings.

Preparation and high temperature tribological properties of microarc oxidation ceramic coatings formed on Ti2AlNb alloy

This present work concentrates on the influence of microarc oxidation ceramic coatings on microstructure and tribological properties of Ti2AlNb alloy. A variety of ceramic coatings are formed on Ti2AlNb alloy in NaAlO2 and Na2SiO3 electrolytes, respectively. A two-step voltage-controlled technology was also used to tailor the microstructure of MAO coatings by adjusting the oxidation time. Microstructure was investigated by using a glancing incidence X-ray diffractometer, a scanning electron microscope, an eddy current thickness meter and a contact surface profiler. The adhesive strength of ceramic coatings to the substrate was tested by a direct pull-off method, and reaches up to 35±3MPa for the two-step voltage-controlled ceramic coatings. Tribological properties of coatings were tested by using a ball-on-disk high temperature friction and wear tester in dry sliding against sintered Si3N4 ball at both room temperature and 600°C. Tribological properties of ceramic coatings are distinctly better than those of Ti2AlNb alloy at both room temperature and 600°C. The dominated wear mechanisms of ceramic coatings are mechanical polishing and brittle microfracturing at room temperature, however, fatigue wear and adhesive wear are also responsible for the material removal at 600oC. The ceramic coatings prepared in the NaAlO2 electrolyte by a two-step voltage-controlled technology have a relatively high wear resistance, and their wear rates are 8.28×10–6mm3N–1m–1 at room temperature and 6.07×10–6mm3N–1m–1 at 600°C. However, the ceramic coatings doped with SiC prepared in the Na2SiO3 electrolyte exhibit low friction coefficients in dry sliding against Si3N4 ball, and their average friction coefficients are 0.45±0.03 at room temperature and 0.55±0.05 at 600°C.

Effects of SiH4 flow rate on microstructure and mechanical properties of TiSiN nanocomposite coatings by cathodic arc ion plating

TiSiN nanocomposite coatings were deposited on Si and cemented carbide substrates by cathodic arc ion plating in SiH4 ambient. The effects of SiH4 flow rate on microstructure, mechanical and tribological properties of the coatings were investigated systemically. Transmission electron microscopy and X-ray diffraction were employed to probe the crystalline microstructure and X-ray photoelectron spectroscopy was used to investigate the chemical bonding states. Microhardness testers and tribometer were used to evaluate the mechanical and tribological properties of TiSiN nanocomposite coatings. The results showed that the structure of TiSiN coating changed from columnar grain to nanocrystalline with increasing SiH4 flow rate. The hardness increased up to 4100 HV0.025 at the SiH4 flow rate of 42 sccm (9.5 at.% Si in the coating), but it decreases with further addition of SiH4 gases. Friction coefficients of TiSiN composite coatings in the range of 0.6–0.7 were obtained when tested against Si3N4 balls.

Structural and tribological properties of TiC-DLC coatings deposited by RCAE-PVD at various bias voltages

The aim of the current study was the evaluation of the bias voltage influence on the structural and tribological properties of titanium carbide dispersed in diamond-like carbon (TiC-DLC) coatings. To this end, TiC-DLC was deposited on 440C stainless steel substrate by physical vapour deposition method with titanium target and acetylene gas sources. The coating process was performed at the constant chamber pressure of 5 mbar and the bias voltage in the range of 100 to 400 V. The coatings were characterised by means of field emission SEM, X-ray diffraction and Raman spectroscopy. Pin on disc test was used for studying the wear behaviour of the coatings. The best tribological properties of coatings were reached at the bias voltage of 200 V. Overall, raising the bias voltage up to 200 V led to the decrease in the wear and friction initially, while getting the higher voltage (up to 400 V) reversed the process.

The Research of Thermal Arc Sprayed Coatings Tribological Properties by Using Rubber Wheel Test

This paper present the result obtained from new experimental STEIN-MESYFIL 953 V; STEIN-MESYFIL 954 V coatings. The surfacing material was wires of 1.6 mm diameter. The tests aimed at determining wear resistance of coatings sprayed on steel substrate. The investigation shows that the tribological behaviour of new experimental thermal arc sprayed coatings is greatly affected by its microstructural constituents such as porosity, oxide inclusions, and microhardness of coatings. Results show that increasing porosity of coatings twice, it doubles the mass loss. Results for thermal sprayed coatings of all experiments showed their high wear resistance and are discussed.

Preparation and Tribological Properties of Graphite-Containing Plasma Electrolytic Oxidation Coatings on Al Alloy

Graphite-containing plasma electrolytic oxidation (PEO) composite coatings were prepared on Al alloy using periodically constant voltage, with addition of graphite in silicate electrolyte. The surface and cross-sectional morphologies of the coatings were examined using scanning electron microscope (SEM), the composition of the coatings was investigated by X-ray diffraction (XRD) and Raman spectra, the tribological properties of the coatings were evaluated on a tribometer. The results show that friction-reducing PEO composite coatings on Al alloy can be prepared in graphite-dispersed electrolyte using periodically constant voltage, the yielded coatings exhibit relatively lower and more stable friction coefficient.

Structure, tribological and electrochemical properties of low friction TiAlSiCN/MoSeC coatings

The present paper is focused on the development of hard tribological coatings with low friction coefficient (CoF) in different environments (humid air, distilled water) and at elevated temperatures. TiAlSiCN/MoSeC coatings were deposited by magnetron sputtering of four-segment targets consisting of quarter circle TiAlSiCN segments, obtained by self-propagating high-temperature synthesis, and one or two cold pressed segments made of MoSe2 and C powders in a ratio 1:1 wt%. The structure and phase composition of coatings were investigated by means of X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The coatings were characterized in terms of their hardness, elastic modulus, and elastic recovery. The tribological properties of coatings were investigated first at room temperature against Al2O3 and WC–Co balls, after which studied in distilled water and during continuous heating in air in the temperature range of 25–400°C against Al2O3 counterpart material. To evaluate their electrochemical characteristics, the coatings were tested in 1N H2SO4 solution. The obtained results show that the coating hardness depends on the amount of MoSeC additives and decreased from 40 to 28 (one MoSeC segment) and 12GPa (two MoSeC segments). Doping with MoSeC resulted in a significant reduction of CoF values measured in humid air (RH 60±5%) from 0.8–0.9 to 0.05 and an increase of wear resistance by one or two orders of magnitude depending on counterpart material. This was attributed to the presence of MoSe2 and free carbon-based phases in the tribological contact. The TiAlSiCN/MoSeC coating with a maximal amount of MoSeC also demonstrated superior tribological characteristics in distilled water (CoF∼0.1) and at moderate temperatures up to 300°C (CoF<0.1). The electrochemical tests showed that, in general, doping with MoSeC did not negatively affect the coating electrochemical behavior. On the contrary, the MoSeC phase demonstrated small positive effect on the anti-corrosive properties of TiAlSiCN coatings under small polarizations.

Effect of energy fluence and Ti/W co-deposition on the structural, mechanical and tribological characteristics of diamond-like carbon coatings obtained by pulsed Nd:YAG laser deposition on a steel substrate

To obtain diamond-like carbon (DLC) coatings, a graphite target was exposed to pulsed Nd:YAG laser radiation (1064nm wavelength) at an energy of 30mJ. The laser fluence was selected so as to initiate either effective plume ionization (80J/cm2) or the greatest deposition rate (9J/cm2). The properties of the coatings at 9J/cm2 were modified through co-deposition of Ti and W atoms. A time-of-flight method was used to study the laser plume. The deposition rate, density, surface morphology, structure and chemical state of the coatings were studied using Rutherford backscattering spectroscopy, X-ray photoelectron spectroscopy, electron energy loss spectroscopy, micro-Raman spectroscopy, atomic force microscopy, and profilometry. The mechanical and tribological properties of coatings were also studied. Loads of 1N or 5N were applied to a steel ball (diameter 3mm) during ball-on-disk sliding tests; only the greater load caused noticeable wear of the coatings. While an increase in the laser fluence decreased the deposition rate by a factor of approximately 18, it also enhanced the maximum energy of ions and the average energy of atoms. As a result, the DLC coating at 80J/cm2 had a density (2.45g/cm3), sp3 content (46%), and hardness (25.4GPa) 1.1–1.2 times greater than the pure DLC coating at 9J/cm2. Moreover, the coating at 9J/cm2 had a rougher surface and microcracks that resulted in pronounced wear of the coating and the counterbody. However, accumulation of wear debris provided for the formation of a low friction tribolayer, so the friction coefficient for this coating was 0.06 or less compared to 0.1 for sliding against the coating obtained at 80J/cm2. Co-deposition of Ti and W suppressed cracking and provided smooth surface coatings. Both elements caused a decrease in the sp3 content and formed chemical bonds with C atoms. However, the increase in wear resistance was evident only with Ti co-deposition.

Microstructural and tribological studies of as-sprayed and heat-treated HVOF Cr3C2–CoNiCrAlY coatings with a CoNiCrAlY bond coat

Die wear is an important problem for manufacturers in hot-working processes, e.g. metal die casting, hot extrusion and thixoextrusion of aluminium, magnesium or steel, as well as glass and plastics processing. The dies have to be capable of withstanding complex thermal and mechanical loads, while giving a sufficient wear resistance against abrasion and adhesion at very high temperatures. In order to improve the wear resistance and reduce the heating of the extrusion die it can be protected with a hard cermet coating. The purpose of this work is to study the high-temperature performance of Cr3C2–CoNiCrAlY coating and explore the potential application of this coating to prolong the life of tooling and dies while reducing maintenance and increasing shelf life and dimensional control. A 75Cr3C2–25CoNiCrAlY coating with a CoNiCrAlY bond coat was sprayed by HVOF thermal spray process on a steel substrate. Coatings were heat-treated at a range of temperatures between 900°C and 1100°C. The mechanical and tribological properties of coatings were determined as a function of the temperature of heat treatment. The bond coat effect on the thermal shock resistance of Cr3C2–CoNiCrAlY coating was analysed.

Tribological properties of self-lubricating TiSiVN coatings at room temperature

In the last years, vanadium rich coatings have been introduced as possible candidates for self-lubrication due to their optimum tribological properties. In the present investigation, the influence of V incorporation on the wear performance of TiSiN films deposited onto WC substrates by d.c. reactive magnetron sputtering is reported. The results achieved for TiSiVN films were compared and discussed in relation to Ti0.80Si0.15N, TiN and Ti0.82V0.15N coatings prepared as references. The tribological properties of the coatings were evaluated at room temperature on a pin on disk tribometer equipment using two different counterparts: Al2O3 and HSS balls. The wear tracks, ball-wear scars and wear debris were characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM–EDS). Tribological tests indicated that the wear rate and the friction coefficient of Ti0.80Si0.15N coating decreased with continuous increase of V content being the overall behavior strongly dependent on the counterpart ball material. For Al2O3 balls the wear rate and friction coefficient of coatings were much lower compared to sliding against HSS steel balls. Ti0.80Si0.15N showed the lowest wear resistance among all tested coatings, independently of the counter-body. For V rich coatings tested with Al2O3 balls the polishing wear mechanism was observed, whereas adhesion wear took place when tested against HSS balls.

Effect of solid lubricant particles on room and elevated temperature tribological properties of Ni–SiC composite coating

In this article, the Ni–SiC, Ni–SiC–MoS2 and Ni–SiC–graphite composite coatings were prepared from a sulfamate bath. Both mechanical and ultrasonic stirrers were used simultaneously during the electrodeposition process. Tribological properties of coatings were evaluated from 25°C to 300°C. Based on the results, the friction coefficient of Ni–SiC composite coating at room temperature is very stable during the wear, but this stability decreases with increasing the test temperature. The incorporation of MoS2 and graphite lubricant particles in the coating reduced the strong adhesive wear and the un-stability of friction coefficient at high temperatures. However, about 15 and 32% reductions were observed in high temperature friction coefficient values of coatings containing MoS2 and Gr particle coatings, respectively. However, the Ni–SiC–Gr composite coating showed the best friction and wear behavior at all temperatures.

Optimization of Composition in Ni(Al)-Cr2O3 Based Adaptive Nanocomposite Coatings

A promising Ni(Al)-Cr2O3-Ag-CNT-WS2 self-lubricating wear-resistant coating was deposited via atmospheric plasma spray of Ni(Al), nano Cr2O3, nano silver and nano WS2 powders, and CNTs. Feedstock powders with various compositions prepared by spray drying were plasma sprayed onto carbon steel substrates. The tribological properties of coatings were tested by a high temperature tribometer in a dry environment from room temperature to 400 °C, and in a natural humid environment at room temperature. It was found that all nanocomposite coatings have better frictional behavior compared with pure Ni(Al) and Ni(Al)-Cr2O3 coatings; the specimen containing aproximately 7 vol.% Ag, CNT, and WS2 had the best frictional performance. The average room temperature friction coefficient of this coating was 0.36 in humid atmosphere, 0.32 in dry atmosphere, and about 0.3 at high temperature.

Surface morphology and tribological properties of DC sputtered nanoscale multilayered TiAlN/CNx coatings

In this study, TiAlN/CNx multilayer and TiAlN monolayer coatings with a CNx top layer were deposited using a reactive DC magnetron sputtering system on cemented carbide tool steel and Si(100) substrates. The morphology and microstructure of the coatings were observed by atomic force microscopy in the dynamic friction mode and transmission electron microscopy. Tribological properties of the coatings were evaluated by pin-on-disc friction testing in dry air, and high-frequency linear-oscillation friction testing in dry air, and under water boundary lubrication conditions. The coatings with a CNx top layer showed better wear behavior and friction coefficients as low as 0.23 and 0.22 for water boundary lubrication. The excellent tribological properties of these composition coatings correspond to their surface morphology and roughness.