A comparative study of the friction and wear behavior of untreated mild steel and its boron-permeated counterpart under lubrication of liquid paraffin containing zinc dialkyldithio-phosphate

AISI-1045 steel was treated with solid boron permeation, and the interaction between the modified surface layer and the lubricating additive zinc dialkyldithio-phosphate (ZDDP) was examined. The friction and wear behavior of the treated and untreated steel specimens were compared. The phase composition of the boron-permeated layer was examined by means of X-ray diffraction. The chemical states of several typical elements on the worn surfaces of the treated and untreated steel surfaces were examined by means of Auger electron spectroscopy and X-ray photoelectron spectroscopy. Results showed that the wear-resistance of boron-permeated specimens was higher than that of the untreated ones. This was partly attributed to the change in the hardness and phase composition of the steel surfaces after boron permeation. Tribochemical reactions between steel and the active elements of the additive occurred during the sliding of the treated and untreated steel discs against an AISI-52100 steel ball using different lubricants. The resultant surface protective films containing various tribochemical products, together with the adsorbed boundary lubricating film, contributed to the reduction of friction and wear.     

Comparative study of the tribological properties of various modified mild steels under boundary lubrication condition

AISI1045 steel was modified by laser heat-treatment and conventional heat treatment. The friction and wear behaviors of the steel specimens after various surface modifications sliding against SAE52100 steel under the lubrication of liquid paraffin containing sulphurized olefin were comparatively investigated on an Optimol SRV oscillating friction and wear tester. The worn surface morphologies of the modified steel specimens were analyzed using a scanning electron microscope. The elemental compositions and chemical states of some typical elements on the worn surfaces of the modified steel specimens were analyzed with an energy dispersive X-ray analyzer and X-ray photoelectron spectroscope, respectively. It was found that the laser heat-treated specimen showed the highest hardness and best wear-resistance. The laser heat-treated and conventionally heat treated AISI1045 steel specimens sliding against SAE52100 steel under the lubrication of liquid paraffin containing sulphurized olefin registered smaller friction coefficients than under the lubrication of liquid paraffin alone. This was partly attributed to the increased hardness of the modified specimens. The tribochemical reaction between the steel and the active elements in the additive was involved in the sliding of the modified steel specimens against SAE52100 steel ball under the boundary lubricating condition, with the formation of a surface protective film composed of various tribochemical products. This also contributed to improve the friction and wear behavior of the modified steel specimens. The steel specimens subject to different surface modifications showed differences in the wear mechanisms under the boundary lubricating condition as well. Namely, the tempered steel specimen was mainly characterized by plastic deformation and pitting, the quenched specimen by grooves and delaminating, and the laser heat-treated one by polishing and mild adhesion.     

The effect of amplitude of vibration on the coefficient of friction for different materials

This work examines how friction coefficients are affected by amplitude of normal vibration at different frequencies. Variation of friction coefficient with the amplitude of normal vibration is investigated experimentally when mild steel pin slides on different types of material such as glass fiber reinforced plastic, cloth reinforced ebonite, polytetrafluoroethylene (PTFE), rubber and mild steel. For this, a pin-on-disc apparatus having facility of vibrating the test samples at different amplitudes and frequencies of vibration was designed and fabricated. During the experiments, the effects of sliding velocity, roughness, normal load and duration of rubbing were also investigated. Studies have shown that the friction coefficient decreases with the increase of amplitude of vibration within the observed range. The observed ranges of amplitude of vibration were 10–200 μm. In this study, it is also observed that the rate of reduction of friction coefficient has a particular relationship on the amplitude and frequency of vibration. The experimental results are compared with those available in the literature and simple physical explanations are provided.     

The effect of frequency of vibration and humidity on the coefficient of friction

Variation of friction coefficient with the variation of frequency of vibration and relative humidity is investigated experimentally on a mild steel disc. A pin-on-disc apparatus having facility of vibrating the disc at different frequency and amplitude is used for the experiment. During the experiment, normal load, speed and relative humidity were varied. The surface conditions of the mild steel base plate were ‘as-turned’ and ‘as-ground’. It is found that friction co-efficient under no vibration condition is higher than that under vibration condition, and the values of friction co-efficient decrease with the increase of frequency of vibration. Similarly, the friction co-efficient decreases with the increase of relative humidity. It is also observed that the rate of reduction of friction co-efficient has a particular relationship with the frequency of vibration and the relative humidity.     

Corrosion inhibition efficiency and adsorption behavior of azomethine compounds at mild steel/hydrochloric acid interface

The adsorption and inhibition effect of azomethine compounds: PhN = NAC (COCH₃) = NC₆H₄Y {Y = OCH₃ (SB₁), CH₃ (SB₂), H (SB₃), Br (SB₄) and Y = Cl (SB₅)} on mild steel in 1 M HCl at 25 °C were studied using gravimetric measurements, cyclic voltammetry, UV–visible Spectrophotométrique and scanning electron microscope (SEM) methods. Inhibition efficiency was found to increase with the increase in azomethine SB₁-SB₅ concentration. The adsorption of each inhibitor on mild steel surface obeys Langmuir adsorption isotherm. The results of cyclic voltammetry showed that the presence of azomethine compound decreases the charge density in the transpassive region. The UV–visible absorption spectra of the solution containing the inhibitor after the immersion of mild steel specimen indicate the formation of a (SB₁-SB₅)-Fe complex. SEM and EDX observations confirmed the existence of protective inhibitor film on a metal surface.     

Friction and wear behaviour of AISI 5140 steel under rectangular wave loading conditions

Abstract

The tribological characteristics and wear mechanisms of AISI 5140 steel at ambient temperature were investigated using a home built ball on disc tribometer under constant normal loading and rectangular wave loading respectively. The worn surface and wear debris collected from the disc were studied using scanning electron microscope. Results show that the friction coefficients under the constant normal force correspond to the traditional theory. The coefficients all exhibited increased normal loads, whereas under the rectangular wave condition, the highest coefficient appeared when the peak value of the periodically alternative load was 90?N. The different underlying wear mechanism under different loading conditions was explored. It was found that abrasive wear was the main mechanism in the constant loading, whereas severe plastic deformation and adhesive wear were the main wear mechanism in the rectangular wave loading cases. This phenomenon can be attributed to the role of debris in the ‘lubrication’ process under the rectangular wave loading conditions.     

Effect of temperature on the frictional behaviour of an aluminium alloy sliding against steel during ball-on-disc tests

Ball-on-disc tests were carried out at elevated temperatures to determine the friction behaviour of the 7475 aluminium alloy against steel, resembling the material mating during hot extrusion. Friction coefficient was found to increase markedly with rising temperature, suggesting that the commonly accepted assumption of an unvaried friction coefficient in the FE simulation of the aluminium extrusion process involving temperature evolution is incorrect. A theoretical analysis showed that the high friction values measured during high-temperature ball-on-disc tests could be partly attributed to the increased plowing friction caused by the severe deformation of the aluminium alloy. The effect of temperature on the stress and strain distributions at the ball/disc interface was revealed by means of three-dimensional finite-element (3D FE) simulation. Increased deformation in the aluminium disc around the contact point with rising temperature was confirmed. The alterations of the strain state and stress state around the contact point were considered responsible for the generation of wear debris, the oscillations of friction coefficient along the wear track and the increase of friction coefficient with rising temperature.     

Friction behavior of laser cladding magnesium alloy against AISI 52100 steel

The use of magnesium alloys in engineering applications is becoming increasingly important as a relatively low density allows savings in energy consumption and therefore reduction in air pollution. An associated reduction in inertia makes these alloys potential candidates for friction components, but they suffer from poor wear resistance. Laser surface alloying with appropriate powder mixture is an innovative technique to improve surface properties of metallic alloys. In this study, the effect of laser surface alloying using Al12%Si powder on wear resistance of a magnesium alloy ZE41 is investigated. Hardness and wear resistance of the alloy are significantly enhanced after treatment.     

The effect of strain-hardening on frictional behavior in tip test

In previous investigation of the tip test using aluminum alloy AL6061-O, it was found that the distance of radial tip from the external side surface of the workpiece deformed has a linear relationship with the maximum forming load measured at a certain punch stroke. In this study, further experiments with aluminum alloys AL2024-O, AL5083-O, AL6061-O, AL7075-O, annealed carbon steel AISI 1010 and pure copper C12100 were carried out to investigate the effect of material properties on frictional behavior by the tip test for the materials commonly used in bulk metal forming. To characterize the relationships among radial tip distance, maximum forming load and shear friction factor, finite element analyses were employed. It was observed that the linear relationships among these three were maintained for the various tested materials. Also, it was found that the friction condition at the punch was always higher than that at the lower die interface such that the ratio of shear friction factors at the die and punch interfaces should be less than one. By examining the material properties currently tested, it was determined that this ratio could be estimated from a logarithmic equation from the value of strain-hardening exponent, depending on the material used.     

Unlubricated sliding frictional behaviour of oxide films on plasma nitrocarburised steel

The sliding frictional behaviour of oxide films formed on low alloy steel by the combined plasma nitrocarburising and post oxidation treatment has been investigated. Unlubricated sliding tests of the as-nitrocarburised and nitrocarburised-oxidised specimens showed that the frictional behaviour depends not only on the oxidation treatment conditions, but also on the counterface material and the testing conditions. When sliding against a steel counterface, all the tested specimens exhibited similar frictional behaviour, which is dominated by the material transfer from the counterface to the sliding surface. On the other hand, when sliding against an alumina slider, all the oxidised specimens exhibited a low friction regime. The duration of this low friction regime depends on the treatment and test conditions, with the low temperature oxidised/nitrocarburised specimen being the most durable. The mechanisms associated with the observed frictional characteristics are discussed in terms of material transfer and the structure and mechanical integrity of the films.     

Analysis of frictional phenomena in friction welding of mild steel

A dynamical analysis of the “equilibrium phase” of friction welding is presented. The fundamental idea is that the observed phenomena are controlled by the behaviour of a viscous layer of plasticised metal at the rubbing surfaces. This layer is postulated to obey a constitutive equation relating shear stress to rate of strain which is similar to the well-known “Bingham plastic” model. Formulae are thus obtained which predict the external driving torque, as well as the thickness and temperature distribution of the plasticised layer. A comparison is made between the theoretical results and a number of experiments which have been carried out on mild steel tubular specimens, over a range of conditions. Good agreement is found in all cases. Preliminary results are presented for the apparent viscosity of plasticised mild steel.     

Investigation of vibration effects on friction and axial force transfer of buckled rod constrained in a horizontal cylinder

The work examines the effects of frequencies of vibrations at different amplitudes on friction force, axial force transfer, and lock-up force of buckled rod constrained in a horizontal cylinder for different media under normal and high temperature environments. Studies have shown that vibrations induced in the rod have significantly reduced friction force, improved axial force transfer and deferred the initiation of critical buckling and lock-up forces for all media in normal temperature environment. Similar trends were observed at higher temperature environments; however, vibration parameters were less effective particularly on very high temperature. Results have also shown that frequency has a particular relationship with the friction force and axial force transfer and employing higher frequency would not improve the results.     

Micro/nano sculpturing of hardened steel by controlling vibration amplitude in elliptical vibration cutting

A new ultra-precision sculpturing method in micro/nano scale for difficult-to-cut materials is proposed in the present research. Elliptical vibration cutting technology is well-known for its excellent performance in achieving ultra-precision machining of steel materials with single crystal diamond tools. Elliptical vibration locus is generally controlled and held to a constant in practice. On the contrary, the proposed method utilizes the variations of the elliptical vibration locus in a positive manner. Depth of cut can be actively controlled in elliptical vibration cutting by controlling vibration amplitude in the thrust direction. By utilizing this as a fast tool servo function in elliptical vibration cutting, high performance micro/nano sculpturing can be attained without using conventional fast tool servo technology. A high-speed amplitude control system is developed for elliptical vibration, with a bandwidth of more than 300 Hz, where the vibration amplitude can be controlled within 4 μm_p-p. The developed control system is applied to sculpturing ultra-precision nano textured grooves on hardened steel with single crystal diamond tools. It is confirmed that the textured grooves have the desired shapes, and their profiles agree well with the vibration amplitude commands input to the control system. Further, a high performance micro/nano sculpturing system for plane surfaces is developed, where the vibration amplitude is controlled in synchronization with the planing motion of an ultra-precision machine tool. Nano sculpturing experiments on hardened steel, carried out by the developed system, are reported, as well as consequent picture images and a variety of dimple patterns that were formed successfully on the hardened steel as nano-scale sculptures.     

Tribological properties of plasma nitrided stainless steel against SAE52100 steel under ionic liquid lubrication condition

1Cr18Ni9Ti stainless steel was modified by plasma nitriding. The phase composition of the plasma nitrided layer was examined by means of X-ray diffraction. The friction and wear properties of the modified and unmodified 1Cr18Ni9Ti stainless steel specimens sliding against SAE52100 steel under the lubrication of ionic liquid of 1-ethyl-3-hexylimidazolium hexafluorophosphate (L-P308) and poly α-olefin (PAO) were investigated on an Optimol SRV oscillating friction and wear tester, with the interactions among the modified surface layer and the ionic liquids and PAO to be focused on. The morphologies of the worn surfaces were observed using a scanning electron microscope. The chemical states of several typical elements on the worn surfaces of the modified steel surfaces were examined by means of X-ray photoelectron spectroscopy. Results showed that the modified sample had better anti-wear abilities than the unmodified one, but the modified sample had a slightly higher friction coefficient than the untreated one. This was partly attributed to the change in the hardness and phase composition of the stainless steel surfaces after plasma nitriding and tribochemical reactions between the steel and the lubricant. The resultant surface protective films composed of various tribochemical products together with the adsorbed boundary lubricating film contributed to reduce the friction and wear.     

Application of diamond-like carbon coatings to elastomers frictional surfaces

Nitrile-butyl rubber-like materials were coated with amorphous hydrogenated diamond-like carbon (DLC) coatings in order to modify their surface and tribological properties. Measurements of water contact angle were performed by the sessile drop method and showed that the coated samples are more hydrophobic with water contact angles up to 116°. The surface free energy of the elastomers was calculated by the acid-base regression method considering polar and dispersive contributions and the results were correlated with changes in the surface chemistry measured by X-ray photoelectron spectroscopy. It has been found that the lower presence of oxygen functional groups on the elastomer surfaces led to lower surface free energies, even though the polar contribution was not predominant. We also found that the DLC coatings led to a significant decrease of the surface free energy (up to 16%) and that there is a good correlation between the surface free energy values and the corresponding water contact angle values. The coefficient of friction was also measured and presented a significant decrease after coating with DLC.     

强化处理对钢球振动值及疲劳寿命的影响

针对钢球表面易产生擦伤，影响钢球精度等原因，采用表面强化处理的方式提高钢球表面质量，降低振动值，提高疲劳寿命。     

Investigation of adhesive and frictional behavior of GeSbTe films with AFM/FFM

Frictional force microscope (FFM) was used to investigate the nanoscale frictional behavior of GeSbTe films deposited by magnetron sputtering. The effects of relative humidity, scanning velocity and surface roughness on friction were taken into account. Besides, the frictional behavior of GeSbTe films with different compositions was analyzed. Experimental results show that the coefficient of friction of GeSbTe films is almost independent of scanning velocity, while the frictional force decreases with increasing velocity. Both the relationship of friction vs. normal load and that of friction vs. RMS keep relatively linear, and the coefficient of friction increases with the increase in RMS. The influence of humidity on adhesion between the tip and the GeSb₂Te₄ film is more significant than that between the tip and the Ge₂Sb₂Te₅ film.     

Effect of surface topography on the frictional behavior at the micro/nano-scale

In this paper, the effect of surface topography on the frictional behavior is investigated at micro/nano-scale in order to better understand the influence of asperity contact angle on friction. Experiments were performed to observe the variation in the frictional force as a spherical ball slides across a grooved surface. Specimens with single and multiple grooves of tens of micrometers in width were fabricated on silicon wafers. The frictional behavior between these specimens and steel balls of different diameters were observed with a tribometer built inside a scanning electron microscope (SEM). Normal load in the range of 20 mN and sliding speed of about 1-6 μm/s were applied in the experiments. It was shown that for relative ball/groove dimension that resulted in low contact angle, the overall frictional force was less than that observed for surface without the groove. Also, in situations where there was a great change in the contact angle stick-slip behavior could be observed. This stick-slip behavior is attributed to mechanical interlocking action.In addition to the above experiments, tests were conducted using lateral force microscopy (LFM). Unlike the previous finding that LFM output is dependent on the slope alone, it was found that the signal was more sensitive to the change in slope, especially when the slope was relatively large. Overall, both micro and nano-scale topographic effect on friction was similar. These results will ultimately aid in design of surface topography for micro-systems for best tribological performance.     

Friction-induced vibration — with and without external disturbance

The dynamics of friction-induced vibration resulting from a velocity-dependent friction characteristic is studied theoretically and experimentally. The frictional system is further studied in the presence of an external dynamic force. The amplitude of quasi-harmonic vibration is shown to increase with sliding velocity until oscillation ceases at some upper velocity boundary depending on the friction characteristic. The vibration, which can exist at high sliding velocities, may influence the operation of automatic transmissions, brakes and clutches. Introduction of strong damping to the system can reduce or eliminate the induced-vibration. Similar results could be achieved by modifying the friction-velocity characteristic of the fluid and materials at the interface. An external excitation in the transverse direction, with properly chosen frequency and force ratios, can also reduce the amplitude of the friction-induced vibration. The theoretical and experimental results are in good agreement.     

Fretting behavior of a rubber coating: Friction characteristics of rubber debris

This paper presents friction characteristics of a rubber coating undergoing fretting-like, oscillatory motion. Results are presented for rubber coated stainless steel as well as uncoated stainless steel experiencing fretting motion. Friction coefficients are experimentally investigated before and after the rubber coating is fully worn out. The effect of load, velocity and displacement amplitude on the friction coefficients of both uncoated and coated stainless steel is discussed.