The structure and tribological behavior of nanocomposite carbide coating on steel 45

It is shown that fullerene black interacts with the steel 45 surface and forms a nanocomposite coating including orthorhombic iron carbide Fe₃C with crystallites sized 100–150 nm and dispersed spots of fullerene black with particles sized 40–50 nm. Tribotests show the coefficient of friction of the composite coating to be three-four times lower and the wear resistance about two times higher than these parameters for original annealed steel 45. It is proved that in friction, frictional transfer occurs of hard high-disperse wear products of the coating carbide base and fullerene black to the counterbody, which encourages the decrease in the friction of the pair with one of its elements coated with Fe₃C-fullerene black. The causes of the improved tribological behavior of the carbide coating are discussed.     

A study of the thermal,dynamic mechanical,and tribological properties of polyphenylene sulfide composites reinforced with carbon nanofibers

The thermal, dynamic mechanical, and tribological properties of polyphenylene sulfide (PPS) composites reinforced with carbon nanofiber (CNF) were studied. Dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC) were used to study the viscoelastic properties and thermal transitions. In order to study the tribological properties, friction and wear tests in a pin-on-disk configuration were performed. The changes in melting point, crystallization temperature, and glass transition temperature were found to be small as a result of reinforcement. Steady state wear rates of the reinforced composites sliding against the counterface of roughness 0.13–0.15 μm Ra were significantly lower than that of the unreinforced PPS. When the composites were tested against the smoother counterface of 0.06–0.11 μm Ra, the wear rates were higher. The coefficient of friction in all the cases was not practically affected by the presence of CNF. The transfer films formed on the counterface during sliding were examined by optical microscopy and atomic force microscopy (AFM). The variation of wear is discussed in terms of the texture and topography of transfer film.     

Tribological behavior of thin electroplated and chemically deposited Ni-P coatings on copper substrates

The paper deals with the study of the tribological behavior of thin (1 and 5 μm thick) Ni-P coatings formed on plates made of electrotechnical copper by electroplating and chemical deposition. It has been found that after heat treatment, owing to diffusion processes, the coating components are capable of penetrating into the substrate material—to a depth of 15 μm for electroplated coatings and of 35 μm for chemically deposited coatings)—and influencing the mechanical properties of a specimen such as the hardness and friction coefficient. A correlation between the wear mode of the coating and the method of its deposition has been found. The results show that thin (one μm thick and lesser) Ni-P chemically deposited coatings are promising for being used in friction units of precise mechanical devices.     

Friction and Wear Properties of IF–MoS2 as Additive in Paraffin Oil

Inorganic fullerene-like (IF) MoS₂ nanoparticles with diameters ranging from 70 to 120 nm were synthesized by desulphurizing the MoS₃ precursor and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Tribological properties of the IF–MoS₂, as lubricating oil additive, were evaluated using a MMW-1 four-ball tribotester. The wear scar was examined with an optical microscope and scanning electron microscopy (SEM). The wear resistance of the paraffin oil was improved and the friction coefficient of the oil was decreased by addition of the IF–MoS₂ nanoparticles. The mechanism of friction and wear of the IF–MoS₂ nanoparticles was discussed.     

Friction and wear of polyphenylene sulfide composites filled with micro and nano CuO particles in water-lubricated sliding

The tribological behavior of polyphenylene sulfide (PPS) composites filled with micro and nano CuO particles in water-lubricated sliding condition were studied. Pin-on-disk sliding tests were performed against a steel counterface of surface roughness 0.09–0.11 μm. The lubrication regimes were established from friction data corresponding to various combinations of loads and sliding speeds. Later experiments were performed using the sliding speed of 0.5 m/s and contact pressure of 1.95 MPa, which corresponded to boundary lubrication regime. Micro CuO particles as the filler were effective in reducing the wear of PPS but nano CuO particles did not reduce wear. The steady state wear rate of PPS-30 vol.% micro CuO composite was about 10% of that of unfilled PPS and the coefficient of friction in this case was the lowest. The examination of the topography of worn pin surfaces of nano CuO-filled PPS by SEM revealed grooving features indicating three-body abrasion. The transfer films formed on the counterfaces during sliding were studied by optical microscopy and AFM. The wear behavior of the composites in water-lubricated sliding is explained using the characteristics of worn pin surfaces and transfer films on the counterface.     

Friction and wear behaviors of nanocrystalline surface layer of medium carbon steel

A nanocrystalline (nc) surface layer, which is about 30 μm thick, was fabricated on a medium carbon steel plate using high-energy shot peening (HESP). The tribological behavior of the nanocrystalline surface layer was investigated under the unlubricated slide using a ring-on-disc tester. The observation of the surface topography shows that the nanocrystalline surface layer may reduce the effect of fatigue wear and improve the friction and wear properties of medium carbon steel. Experimental results show that the friction coefficient and wear weight loss decrease and the wear resistance increases with the surface nanocrystallized samples under lower loads.     

The effect of copper concentration on the wear resistance of composites based on recycled ShKh15 steel during friction with current collection

The current-voltage characteristic, wear resistance, and friction surface roughness of baked model copper-graphite-ShKh15 steel composites are determined. It is shown that the composites containing under 10% and above 50% Cu produce a friction zone with low conductivity and wear resistance. The composites containing 15–20% Cu produce a friction zone with relatively high conductivity and wear resistance. The maximum parameters of the roughness (R _a = 2.98 μm and R _z = 24.5 μm) appear on the friction surface of the material containing 50% Cu.     

Structure and wear resistance of electron-beam nitrous coatings

The paper deals with the study of the tribological properties of nitrogen-containing austenite coatings deposited by electron-beam facing during abrasive wear and the sliding friction of a VK6 hard alloy indentor. The abrasive wear resistance of the nitrous coatings deposited by the electron-beam facing of steel 60Kh24AG16 powder in quartz sand is lower than that of the steel 65G coatings after hardening; it increases with increasing mass share of the filler. At contents of nitrided ferrovanadium of 10?C30 wt % the abrasive wear rate increases by 30?C50%, respectively. It is found that under a certain load applied to the VK6 ball indentor the friction coefficient and the shear resistance of the surface layer diminish. It is shown that under heavy specific loads applied to the ball indentor the nitrous coating faced from steel 60Kh24AG16 powder and composite nitrous coatings have wear resistance exceeding that of steels 110G13 and Kh18N10 by more than two and seven times, respectively. Based on the results of structural studies an explanation of the observed behavior of the nitrous coatings is proposed.     

Tribological Characteristics of Oxide Layer Formed on TiN Coated Silicon Wafer

The effects of the oxide layer formed on the wear tracks of a titanium nitride (TiN) coated silicon wafer on friction and wear characteristics were investigated. Silicon wafers were used as the substrate of coated disk specimens, which were prepared by depositing TiN coating with 1.74 m in coating thickness using the arc ion-plating method. SAE 52100 steel balls were used as the counter-faces. The tests were performed both in air for forming an oxide layer on the wear track and in nitrogen to avoid oxidation. This paper reports the characterization of the oxide layer and its effects on friction and wear characteristics using Auger electron spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The TiN coating with the oxides shows relatively high friction compared to that without an oxide layer. The thickness of the layer formed on the surfaces of the TiN coated silicon wafer is very thin compared to the thickness of the TiN coating. The oxide layer dominates the frictional characteristics between the two materials and induces a relative high friction.     

Experimental Evaluation of Friction and Wear Properties of Solid Lubricant Coatings on SUS440C Steel in Liquid Nitrogen

The friction and wear properties of the prevailing different solid lubricant coatings (Ion-plated Au, Ion-plated Ag and RF-sputtered PTFE on SUS440C stainless steel) used in the bearings of high-speed cryogenic-turbo-pumps of liquid rocket engines were experimentally evaluated in liquid nitrogen immersed conditions. Also the above experiments were carried out with two newly proposed solid lubricant coatings of sputter-ion-plated MoSTi and a new ion-plated Pb on SUS440C stainless steel. The friction coefficient and wear rates of the coatings of ion-plated Au, ion-plated Ag, RF-sputtered PTFE, the new ion-plated Pb and MoS₂Ti-SIP (with coating thickness of 0.7±0.1 μm) on SUS440C steel against SUS440C stainless steel ball in liquid nitrogen were compared. Worn surfaces were examined microscopically with a microscope and a profilometer for understanding the mechanisms of friction and wear and transfer film lubrication in liquid nitrogen. It is found that the newly proposed solid lubricant coatings are showing promising results for their use in liquid nitrogen immersed conditions. The sputter-ion-plated MoSTi coating on SUS 440C steel shows a minimum value of friction coefficient (μ=0.015) and wear rate (w_c=0.56 × 10⁻⁶ mm³/N m ) in liquid nitrogen.     

Effect of wear debris on antifriction and antiwear properties of industrial oils I-20A and I-40A in friction of steel surfaces

The effect of wear debris on the antifriction and antiwear properties of industrial oils I-20A and I-40A in boundary sliding of steel against steel is studied. Variations in the tribological characteristics, including the friction coefficient, linear and energy wear rates, carrying capacity, and others, are studied during running-in and friction of run-in contacts. Among the specified concentrations of wear debris, the concentration of 0.8–1.0 mg/ml is found to be inadmissible and requires oil replacement. The temperature dependences of the friction coefficient for run-in contacts are obtained. It is shown that in all cases the properties of oil I-40A surpass those of oil I-20A.     

Deposition and Nanotribological Characterization of Sub-100-nm Thick Protective Ti-Based Coatings for Miniature Applications

Ti-based protective thin films with thicknesses below 100 nm, intended for miniature applications were deposited using physical vapor deposition magnetron sputtering. X-ray diffraction (XRD), scanning electron microscopy, and atomic force microscopy were employed for the assessment of microstructure, morphology, film thickness, surface topography, and roughness. XRD pattern showed the formation of f.c.c TiN, TiCN, and TiC phases with different preferred orientations for films prepared in Ar/N₂, Ar/N₂ + C₂H₂, and Ar/C₂H₂ gas mixtures, respectively. Nanotribological performance was investigated using multipass nanoscratch technique at variable applied normal loads (100–400 μN). The nanoscale coefficient of friction was found to be in the 0.08–0.1 range, a sufficiently low value showing the potential of these films for miniature applications, such as microelectromechanical systems. The nanowear resistance at mean contact pressures in the range of 5–8.5 GPa for each sample was evaluated in terms of the average residual wear depth and an abrasive-dominated wear mechanism was found.     

The Tribological Behaviour of Fe–28Al–5Cr/TiC Under Liquid Paraffine Lubrication

The tribological behaviour of Fe–28Al–5Cr and its composites containing 15, 25 and 50 wt% TiC (corresponding to 19.3, 31.2 and 57.6 vol%), produced by hot-pressing process, was investigated under liquid paraffine lubrication against an AISI 52100 steel ball in ambient environment at varied applied loads and sliding speeds. It was found that the wear resistance increased and friction coefficient decreased with increasing of TiC content. The coefficients of friction are in the range of 0.09–0.14 at the given testing conditions. The wear rates of all the materials except the 50% composite are on the order of 10⁻⁶–10⁻⁵ mm³ m⁻¹, the wear rate for the 50% composite is too low to quantify under the two sliding conditions, (50 N, 0.04 m/s) and (100 N, 0.02 m/s). The wear rates of all the materials increase as applied load increases and the increasing extent diminishes with the increase of TiC content, but first increase slightly and then nearly remains steadiness with increasing sliding speed. The 50 wt% composite has wear resistance about 7–20 times better than pure Fe–28Al–5Cr at different sliding parameters. The enhanced wear resistance by TiC addition is attributed to the high hardness of the composites, as well as support of the oil lubrication film/layer by the hard TiC phase. The worn surfaces of all the materials are analyzed by a scanning electron microscope. The dominant wear mechanism of the Fe–28Al–5Cr and 15% composite is grooving and flaking-off, but those of the 25 and 50% composites are mainly shallow grooving.     

Tribological Behavior of Bronze Composite Coatings Obtained by Plasma Thermal Spraying

Bronze aluminum composite coatings containing different amounts of alumina were fabricated by plasma spray process and their tribological properties were investigated using ball-on-disk (BOD) and rubber wheel (RW) tests at room temperature. Main wear mechanisms in pure bronze coatings during the ball-on-disk friction test were abrasion and intersplat delamination. The addition of alumina in bronze coatings clearly enhances their wear resistance. To explain this behavior, this article proposes an additional wear mechanism in the composite coatings that involves the rupture of the alumina lamellae located just below the wear track leading to a uniform distribution of fine alumina particles enveloped by the bronze matrix, which increase the surface hardness and hinder the wear. The deposition of debris on the wear track of composite coatings provokes an enhancement of the wear resistance as well. Bronze coatings show a low and stable friction coefficient of around μ = 0.3. Nevertheless, coatings with reinforcing particles of alumina show an abrupt transition in the friction coefficient from values around μ = 0.4–0.8, related to the modification of the surface contacts on the wear track due to the formation of a compacted debris layer deposited during the tribological test.     

Tribological Behaviour of N(C)-Alloyed W–S Films

In this study, sputtered W–S–N(C) films were deposited by rf magnetron sputtering with increasing N or C content. The coatings were tribologically tested in a pin-on-disk apparatus with increasing applied normal loads in two different environmental conditions, normal room atmosphere and dry nitrogen atmosphere. W–S–N(C) films without or with low N(C) addition had high wear rates, whatever the environment was, but induced low wear in the counterbody material and low friction coefficients. The coatings alloyed with high N content showed excellent wear resistance and a very low friction coefficient (<0.05) when tested in dry nitrogen but the opposite behaviour under room conditions. For their part, high C-containing coatings showed an excellent tribological behaviour in both environments, not as good as N-alloyed films in dry nitrogen but much better under room conditions. The wear and friction coefficients were lower in dry nitrogen than in humid air. Globally, the alloying with N(C) resulted in wear rates in W–S–N(C) films two orders of magnitude lower than in an unalloyed one, keeping the friction coefficient at the same level or even lower. The wear behaviour was interpreted as a function of several factors including; the mechanical strength of the coatings, the adhesion of the films to the substrate, the porosity and the structural arrangement of the film.     

Tribological Performance of UHMWPE and PFPE Coated Films on Aluminium Surface

A thin layer of Ultra High Molecular Weight Polyethylene (UHMWPE) or UHMWPE + PFPE is coated onto cylindrical aluminium (Al) pin (4.6 mm diametre) surface with the aim of providing wear resistant coating on this soft and tribologically poor metal. The coefficient of friction and wear life of the coated samples are investigated on a pin-on-disk tribometre under different normal loads (394–622 g) and two sliding speeds (0.1 and 0.31 m/s) against uncoated Al disk as the counterface. Both coatings provide coefficient of friction values in the range of 0.02–0.2 as compared to 0.4–1.0 for uncoated Al. There is tremendous improvement in the wear life of the pin, with UHMWPE + PFPE film giving wear life approximately twice to thrice higher than that with only UHMWPE film. A thin polymer film is transferred to the disk surface during sliding providing very long-term wear life (continuous low coefficient of friction) despite visual removal of the film from the pin surface. The present films will have applications in gears and bearings as solid or boundary lubricants for automotive and aerospace component.     

Friction and wear properties of rice husk ceramics under dry condition

The friction and wear behaviors of rice husk (RH) ceramics, prepared by carbonizing the mixture of rice husk and phenol resin at 900 °C in N₂ gas environment, sliding against high carbon chromium steel (JIS SUJ2), austenitic stainless steel (JIS SUS304), and Al₂O₃ under dry condition were investigated using a ball-on-disk tribometer. The test results show that the friction coefficient of RH ceramics takes very low values 0.05–0.08 and 0.06–0.11 sliding against SUJ2 and SUS304, respectively, and much higher values around 0.14–0.23 against Al₂O₃. It was also shown that SUJ2 provides the lowest specific wear rate values below 10⁻⁹ mm²/N, while, those of SUS304 and Al₂O₃ mostly stayed between 10⁻⁹ to 10⁻⁸ mm²/N range. The worn surfaces of counterparts were observed with optical microscopy and analyzed using cross-sectional transmission electron microscopy with energy dispersive X-ray spectroscopy and electron diffraction. It was suggested that the tribological behaviors of RH ceramics are closely related with the formation of a transferred film, consisted of amorphous silica and carbon particles, on a counterpart surface. The transferred film was formed readily on SUJ2 balls, whereas for SUS304 the presence of the film was subject of the sliding conditions. Moreover, formation of the transferred film could not be detected on Al₂O₃ counterparts.     

The Effect of Steel Hardness on the Performance of ZDDP Antiwear Films: A Multi-Technique Approach

X-ray absorption near-edge structure (XANES) analysis has been used to characterize the chemistry of antiwear films formed in a mineral base oil containing a zinc dialkyl dithiophosphate (ZDDP) additive. These films were formed by rubbing the AISI 1095 steel samples under a reciprocating boundary contact. The steel samples were tempered to produce different Vickers hardness values. The phosphorus L-edge XANES spectra show that these films differ slightly in their chemical nature, with longer chain polyphosphates being formed on samples with higher hardness value. The surface morphology of the films was investigated using Atomic force microscopy (AFM) and the film thickness was probed by Focussed ion beam and Scanning electron microscopy (FIB/SEM) techniques. Furthermore, the nanomechanical properties of these antiwear films were investigated by nanoindentation methods. Tribological measurements of the coefficient of friction (μ) and wear scar width (WSW) indicate that the poorest antiwear film was formed on the softest substrate, which exhibited the largest WSW and the highest average μ. FIB/SEM images show that the thicknesses of the antiwear pads and the degree of damage on the substrates both change with the hardness value of the samples.     

Tribological behaviors and mechanisms of Ti<Subscript>3</Subscript>AlC<Subscript>2</Subscript>

Tribological behaviors and the relevant mechanism of a highly pure polycrystalline bulk Ti₃AlC₂ sliding dryly against a low carbon steel disk were investigated. The tribological tests were carried out using a block-on-disk type high-speed friction tester, at the sliding speeds of 20–60 m/s under a normal pressure of 0.8 MPa. The results showed that the friction coefficient is as low as 0.1∼0.14 and the wear rate of Ti₃AlC₂ is only (2.3–2.5) × 10⁻⁶ mm³/Nm in the sliding speed range of 20–60 m/s. Such unusual friction and wear properties were confirmed to be dependant dominantly upon the presence of a frictional oxide film consisting of amorphous Ti, Al, and Fe oxides on the friction surfaces. The oxide film is in a fused state during the sliding friction at a fused temperature of 238–324 °C, so it takes a significant self-lubricating effect.     

Tribological Properties of TiN/Ag Nanocomposite Coatings

Morphology, structure, and tribological behavior of magnetron co-sputtered TiN/Ag nanocomposite coatings deposited at 150 °C with an Ag content in the range of 7–45 at.% were characterized. The coatings show a columnar structure with embedded Ag crystallites of 3–50 nm in diameter, where the columns are characterized by a layered structure with Ag-poor and Ag-rich layers. These layers originate from sample rotation during deposition, where the layer thickness increases with increasing Ag content. These Ag layers become continuous over a critical Ag content. At room temperature the friction coefficient is determined by the film structure, whereas friction and wear at high temperature depend on segregation of Ag to the surface.