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This study aims to investigate the surface modification on 20CrMnTi gear steel individually treated by diamond-like carbon films and nitride coatings.

For this purpose, the mechanical properties of a-C:H, ta-C and AlCrSiN coatings are characterized by nano-indentation and scratch tests. The friction and wear behaviors of these three coatings are evaluated by ball-on-disc tribological experiments under dry contact conditions.

The results show that the a-C:H coating has the highest coating-substrate adhesion strength (495 mN) and the smoothest surface (Ra is about 0.045 µm) compared with the other two coatings. The AlCrSiN coating shows the highest mean coefficient of friction (COF), whereas the ta-C coating exhibits the lowest one (steady at about 0.16). The carbon-based coatings possess excellent self-lubricating properties compared with nitride ceramic ones, which effectively reduce the COF by about 64%. The major failure mode of carbon-based coatings in dry contact is slight abrasive wear. The damage of AlCrSiN coating is mainly adhesive wear and abrasive wear.

It is suggested that the carbon-based film can effectively improve the friction-reducing and wear resistance performance of the gear steel surface, which has a promising application prospect in the mechanical transmission field.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2023-0129/

This paper aims to investigate the correlation between wear behavior and microstructure evolution in friction-induced deformation layers (FDL) of 30CrMnSi steel, especially the role of strain-hardening induced by plastic deformation in FDL, which accordingly alters the wear behavior.

Dry sliding friction and wear behaviors of the 30CrMnSi steel against quenched and tempered GCr15 steel were studied using a pin-on-disc tester. The microstructure, hardness and plastic deformation of FDL were investigated.

It was found that the evolution of microstructure and strain-hardening induced by plastic deformation were occurred in the subsurface. When the microstructure, hardness and depth of the plastic deformation layer (PDL) reached a relatively steady state, the friction process transformed into stable-state stage. The wear loss and depth of the PDL was in dynamic equilibrium at stable wear stage.

In this paper, the correlation among the microstructure evolution, the strain-hardening and wear behavior were systemically analyzed. This paper could provide a theoretical reference for optimizing the microstructure and strain hardening properties of tribo-pairs materials.

This paper aims to study the micro-structure evolution of friction layers to optimize the friction and wear behaviors of TiAl-based material. It further enlarges the scope of using TiAl alloys and increase in the service life of TiAl alloy-made mechanical components, especially under some extreme conditions.

To study the structure evolution of friction layers, the HT-1000 tribometer is used to study the friction and wear properties of as-prepared samples. With the assistance of field emission scanning electron microscopy and an electron probe micro-analyzer, the stratified structures in cross-sections and a surface morphology of the wear scars are well characterized. A ST400 surface profiler helps in better understanding of the three-dimensional texture profiles of wear scars. X-ray diffractometer (XRD) is also used to analyze phases in the as-prepared samples.

An analysis method on the micro-structure evolution can provide better views to understand the influence of friction layers on the tribological behavior, at different wear stages. It finds that the micro-structure evolution of friction layers has an immediate effect on the friction coefficients and wear rates of TiAl-based material. It also proves to be a useful tool for evaluating the behaviors in friction and wear of TiAl-based material.

The findings of this paper provide better assistance to explore the effect of friction layers on the friction and wear behaviors of TiAl-based materials. The results help in deep understanding of the micro-structure evolution of friction layers. It also increases the service life of TiAl-based mechanical components.

The purpose of this study is to investigate the effects of nanoadditive lubricants on the vibration and noise characteristics of helical gears compared with conventional lubricants. The experiment aims to analyze whether nanoadditive lubricants can effectively reduce gear vibration and noise under different speeds and loads. It also analyzes the sensitivity of the vibration reduction to load and speed changes. In addition, it compares the axial and radial vibration reduction effects. The goal is to explore the application of nanolubricants for vibration damping and noise reduction in gear transmissions. The results provide a basis for further research on nanolubricant effects under high-speed conditions.

Helical gears of 20CrMnTi were lubricated with conventional oil and nanoadditive oils. An open helical gearbox with spray lubrication was tested under different speeds (200–500 rpm) and loads (20–100 N·m). Gear noise was measured by a sound level meter. Axial and radial vibrations were detected using an M+P VibRunner system and fast Fourier transform analysis. Vibration spectrums under conventional and nanolubrication were compared. Gear tooth surfaces were observed after testing. The experiment aimed to analyze the noise and vibration reduction effects of nanoadditive lubricants on helical gears and the sensitivity to load and speed.

The key findings are that nanoadditive lubricants significantly reduce the axial and radial vibrations of helical gears under low-speed conditions compared with conventional lubricants, with a more pronounced effect on axial vibrations. The vibration reduction is more sensitive to rotational speed than load. At the same load and speed, nanolubrication reduces noise by 2%–5% versus conventional lubrication. Nanoparticles change the friction from sliding to rolling and compensate for meshing errors, leading to smoother vibrations. The nanolubricants alter the gear tooth surfaces and optimize the microtopography. The results provide a basis for exploring nanolubricant effects under high speeds.

The originality and value of this work is the experimental analysis of the effects of nanoadditive lubricants on the vibration and noise characteristics of hard tooth surface helical gears, which has rarely been studied before. The comparative results under different speeds and loads provide new insights into the vibration damping capabilities of nanolubricants in gear transmissions. The findings reveal the higher sensitivity to rotational speed versus load and the differences in axial and radial vibration reduction. The exploration of nanolubricant effects on gear tribological performance and surface interactions provides a valuable reference for further research, especially under higher speed conditions closer to real applications.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2023-0220/

The restoration and strengthening of QT600 is an industry bottleneck challenge. The Co-12 cladding layer has great wear and corrosion resistance. The purpose of this paper is to quantitatively reveal the transient evolution law of the corrosion process of Co-12 cladding layer on QT600 surface.

In this paper, a three-dimensional numerical model of the corrosion process of Co-12 cladding layer by QT600 laser cladding is established. The interaction between pitting pits and corrosion medium is considered to reveal the transient evolution of ion concentration, electrode potential, pH and corrosion rate at different locations.

The calculation shows that the ion concentration in pitting pit changes Cl⁻>Co²⁺>Na⁺, pH value decreases from top to bottom and corrosion rate at bottom is greater than that at top. The electrochemical corrosion test of Co-12 cladding layer was carried out. It is shown that the current density of QT600 increases by an order of magnitude compared to the Co-12 cladding layer, and the corrosion rate is 4.862 times higher than that of the cladding layer.

The results show that Co-12 cladding layer has great corrosion resistance, which provides an effective way for QT600 protection.

This paper aims to investigate the energy-saving effect and mechanism of serpentine as lubricant additive in the simulated condition.

An ABLT-1 bearing test machine was used for 1,350 hours and an MM-W1 three-pin-on-disk apparatus was used to investigate its anti-friction effect. The worn surface was characterized by scanning electron microscopy equipped with energy dispersive spectroscopy.

The results show that the energy-saving effect was improved after adding serpentine powder in oil and that both the friction coefficient and mass loss were dramatically decreased. The analysis on worn surface layer demonstrates that an auto-reconditioning surface layer was formed on the worn surface, which was responsible for the decrease in friction and wear.

The simulation test for the metal bearing was conducted over 1,350 hours using lubricant with and without serpentine powder. The addition of serpentine powder enhanced the energy-saving rate over time, stabilizing at about 13 per cent after 1,000 hours. An auto-reconditioning surface layer was formed on the surfaces of disassembled bearing lubricated with serpentine doped oil, resulting in dramatic decrease of both the friction coefficient and the mass loss. In addition to normal load and the accumulation of serpentine powder in the furrows and scratches of the deformed layer, the formation of the surface layer was possibly related to the substrate deformation induced by friction force.

This paper aims to elucidate the effects of lubricant groove shape, vertical load, swing angle and grease injection cycle on the friction and wear performances of journal bearings under the grease lubrication condition.

Three different types of lubricant grooves, namely, numeral eight-shaped, axial straight line-shaped and circular blind hole-shaped, were designed and machined in the bearing bush of journal bearings. The tribological behaviors of these journal bearings were investigated on the self-developed reciprocating swing friction and wear tester. Experimental data including the friction coefficient, the friction temperature, the wear loss and wear time were analyzed in detail. The wear morphologies of friction pairs were observed by scanning electron microscope and confocal laser scanning microscope.

The load carrying capacity and service life of the journal bearing with circular blind hole-shaped lubricant grooves are not affected. However, the load carrying capacities of journal bearings with numeral eight-shaped and axial straight line-shaped lubricant grooves are declined. The coverage areas of lubricating grease in the bearing bush are associated with the swing angle. The smaller the swing angle is, the more limited the coverage areas of lubricating grease get. Among these journal bearings, the maintenance-free time of journal bearing with circular blind hole-shaped lubricant grooves is the longest because of its large grease storage capacity.

The journal bearing with circular blind hole-shaped lubricant grooves exhibits the excellent antifriction and wear-resistant properties, making it suitable for the application in the low-speed and heavy-load engineering conditions.

The severe friction and wear of the spindle in a cotton picker often occur in a picking cotton, which affects the spindle lifetime and its efficiency of picking cottons. This paper aims to investigate the effect of an electroless nick coating on the spindle performances to avoid its abnormal phenomena.

First, it is coated on the surface of the test specimen with the material same as that of the spindle. Then, the friction coefficient and wear for the coating are measured under oil lubrication to evaluate its effect in improving the tribological performances for the spindle.

The stabilized friction coefficient of the electroless nick coating decreases with increasing reciprocating frequency of specimen and increasing applied load. There exists a critical coating thickness yielding the smallest friction coefficient. Moreover, this coating has a property of the smaller friction coefficient in comparison with a hard chromium coating.

The research about the electroless nick effect on the spindle’s tribological performances is not found yet to date. To avoid severe friction and wear of the spindle, this paper investigated how the reciprocating frequency of specimen, applied load and coating thickness affect the spindle’s tribological performances. The associated conclusions can provide a reference to enhance the spindle lifetime and its transmission efficiency.

Streak defect and dynamic harmonic excitation (DHE) loading play important roles in machine operating conditions. The purpose of this paper was to assess the effects of streak defect and DHE loading on the tribological properties of surface-contact friction pairs, for example the differential gear end-face on the washer, via experimental investigation.

Streak defect was artificially introduced into the washer surface, which was loaded with DHE loads produced by a spring-connecting weight system. The wear scar of the washers and the monitored friction force signals were respectively scanned using scanning electron microscope (SEM) and analyzed using wavelet simulation.

The friction force curves, SEM images and discrete wavelet transform results indicate that DHE loading tends to increase friction force, to accelerate plowing damages and result in side-flow of material and plastic deformation on the surfaces of the washer. Whereas, streak oil-channel textures on washer specimen can be machined to modify the lubrication condition in the running-in stage so as to improve the tribological properties of the sliding pairs which were even subjected to DHE loading.

On the basis of this thesis research, the effect of streak defect and DHE loading on tribological performance of surface-contact sliding pairs is discussed. The results of wear form and friction state with the effect of streak defect and DHE loading facilitate to optimize the operating condition of mechanical parts.