Search results

Through practical tests, it has been found that steel balls based on different standards could affect tribological performances of the same lubricant, but unfortunately, past researches in the field have been quite inadequate. The aim of this paper, therefore, is conscientiously to study the problem.

The anti‐wear properties of four kinds of lubricants were evaluated by four‐ball tester using two kinds of steel balls based on different standards. The reason for different anti‐wear properties of the same lubricant was also discussed using hardness tester and scanning electron microscope with an energy dispersive spectrometer (SEM/EDS).

It was found that steel balls based on different standards could affect the tribological results for the same lubricant. The reason could lie in the surface chemical composition, surface roughness and hardness of steel balls which originated from the subtle difference of different standards.

The paper shows that, as far as evaluating anti‐wear properties is concerned, steel ball based on AISI Standard Steel No. E‐52100 is a better choice than that based on Chinese standard GB 308.

The purpose of this paper is to study the tribological behavior of hardened, boronized and boro‐chromized AISI 52100 steel balls against boro‐chromized AISI 1040 steel disk under 2, 5 and 10 N loads at 0.1 and 0.3 m/s sliding speeds.

Boronizing treatment was realized at 1,000°C for 2 h in a slurry salt bath consisting of borax, boric acid and ferro‐silicon. Some of the boronized steels were chromized at 1,000°C for 2 h by pack method in the powder mixture consisting of ferro‐chromium, ammonium chloride and alumina. Similarly, AISI 1040 steel disk was boronized at 900°C for 4 h in the same bath and then chromized by pack method. Friction and wear tests were carried out using a ball‐on‐disk machine.

The results showed that the specific wear rate of hardened and boronized AISI 52100 steel balls decreased with increasing load and decreasing sliding speed. Untreated AISI 52100 steel balls showed much greater specific wear rate than the boronized and boro‐chromized AISI 52100 steel balls. Boronized steel balls exhibited the highest wear resistance. The specific wear rates of hardened, boronized and borochromized steel balls were between 9.6422 × 10⁻⁵ and 1.6714 × 10⁻⁴, 4.4079 × 10⁻⁶ and 3.2829 × 10⁻⁵, and 1.0135 × 10⁻⁵ and 3.0559 × 10⁻⁵ mm³ N⁻¹ m⁻¹, respectively. The lowest coefficient of friction was recorded on a boro‐chromized steel disk, tested against boronized steel ball at 0.3 m/s sliding speed and under low‐load value.

Tests have been made on the basis of atmospheric conditions. The study can be detailed using some lubricants on the wear test.

The research has shown that boronizing and boro‐chromizing treatments realized on steels have a good wear resistance in the open atmosphere. Boronizing treatment has been used for tribological applications for a long time. Boro‐chromizing treatment can be applied on steels, successfully.

Tribological properties of boro‐chromized steels are explained in the present study for the first time.

The purpose of this paper was to explore the mechanisms of scuffing propagation of heavily loaded lubricated friction pair elements coated with low-friction WC/C coating for various material combinations.

The investigations were performed for low-friction coatings WC/C (a-C:H:W) deposited by the reactive sputtering physical vapour deposition (PVD) process. Experiments were carried out using a four-ball tester with continuously increasing loads. Tests were conducted for the following four material combinations: steel/steel tribosystem (all balls uncoated); steel/coating tribosystem (one upper ball uncoated/three lower balls WC/C-coated); coating/steel tribosystem (one upper ball WC/C-coated/three lower balls uncoated); and coating/coating tribosystem (all balls WC/C-coated).

The better scuffing resistance is achieved by coating only one element (coating/steel tribosystem) than all elements (coating/coating tribosystem). The description of scuffing propagation for all investigated tribosystems was done. The high scuffing resistance of the coating/steel tribosystem resulted from reducing the adhesion between rubbing surfaces due to low chemical affinity (similarities) between the steel and the coating material and the presence of solid lubricant in the friction zone.

In all cases, when a coating is applied, an increase in scuffing resistance is observed. However, it is better to coat only one element than all. Furthermore, the scuffing resistance for the coating/steel tribosystem is significantly higher than for the steel/coating tribosystem.

The main value of this paper is description of scuffing propagation and revealing the new aspects in application of low-friction WC/C coating for heavily loaded lubricated friction pair elements. The overlapping ratio has been defined as an important factor influencing the scuffing resistance of the coated tribosystems.

This paper aims to improve the tribological properties of lithium complex greases using nanoparticles to investigate the tribological behavior of single additives (nano-TiO₂ or nano-CeO₂) and composite additives (nano-TiO₂–CeO₂) in lithium complex greases and to analyze the mechanism of their influence using a variety of characterization tools.

The morphology and microstructure of the nanoparticles were characterized by scanning electron microscopy and an X-ray diffractometer. The tribological properties of different nanoparticles, as well as compounded nanoparticles as greases, were evaluated. Average friction coefficients and wear diameters were analyzed. Scanning electron microscopy and three-dimensional topography were used to analyze the surface topography of worn steel balls. The elements present on the worn steel balls’ surface were analyzed using energy-dispersive spectroscopy and X-ray photoelectron spectroscopy.

The results showed that the coefficient of friction (COF) of grease with all three nanoparticles added was low. The grease-containing composite nanoparticles exhibited a lower COF and superior anti-wear properties. The sample displayed its optimal tribological performance when the ratio of TiO₂ to CeO₂ was 6:4, resulting in a 30.5% reduction in the COF and a 29.2% decrease in wear spot diameter compared to the original grease. Additionally, the roughness of the worn spot surface and the maximum depth of the wear mark were significantly reduced.

The main innovation of this study is the first mixing of nano-TiO₂ and nano-CeO₂ with different sizes and properties as compound lithium grease additives to significantly enhance the anti-wear and friction reduction properties of this grease. The results of friction experiments with a single additive are used as a basis to explore the synergistic lubrication mechanism of the compounded nanoparticles. This innovative approach provides a new reference and direction for future research and development of grease additives.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-09-2023-0291/

This paper aims to investigate the preparation of AlN and Al₂O₃, as well as the effect of nano-AlN and nano-Al₂O₃, on friction and wear properties of copper-steel clad plate immersed in the lubricants.

Nano-AlN or nano-Al₂O₃ (0.1, 0.2, 0.3, 0.4 and 0.5 Wt.%) functional fluids were prepared. Their tribological properties were tested by an MRS-10A four-ball friction tester and a ball-on-plate configuration, and scanning electron microscope observed the worn surface of the plate.

An increase in nano-AlN and Al₂O₃ content enhances the extreme pressure and anti-wear performance of the lubricant. The best performance is achieved at 0.5 Wt.% of nano-AlN and 0.3 Wt.% of nano-Al₂O₃ with PB of 834 N and 883 N, a coefficient of friction (COF) of approximately 0.07 and 0.06, respectively. Furthermore, the inclusion of nano-AlN and nano-Al₂O₃ particles in the lubricant enhances its extreme pressure performance and reduces wear, leading to decreased wear spot depth. The lubricating effect of the nano-Al₂O₃ lubricant on the surface of the copper-steel composite plate is slightly superior to that of the nano-AlN lubricant, with a COF reaching 0.07. Both lubricants effectively fill and lubricate the holes on the surface of the copper-steel composite plate.

AlN and Al₂O₃ as water-based lubricants have excellent lubrication performance and can reduce the COF. It can provide some reference for the practical application of nano-water-based lubricants.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2023-0255/

Babbitt bush is easy to cause severe adhesive wear due to unexpected journal fall. This paper aims to improve wear resistance of Babbitt bush.

A soft/hard hybrid surface mircoprofile of Babbitt alloy/steel was fabricated by a technology of laser texture combined with hot-pressing. The friction and wear performances of bare steel (steel-h), Babbitt bush on steel (steel-s) and Babbitt filled in dimples of steel (steel-hs) were conducted on a ball-on-disc tester under dry and lubricated conditions.

The results showed that wettability of steel-hs was enhanced by forming soft/hard hybrid surface. Compared with steel-s, the stability of friction coefficient curve of steel-hs was improved without increasing coefficient friction. The wear resistance of steel-hs was remarkably enhanced under dry and lubricated conditions.

The originality of this paper is as following: to improve the tribological properties and to prolong service life of steel-s, soft/hard hybrid surface of Babbitt filled in dimples of steel substrate was successfully fabricated by laser texturing combined with hot-pressing. This paper showed that the lipophilicity of steel-hs was best among those of steel-s and steel-h. Babbitt alloy as a soft filler on dimples of steel substrate improved anti-wear of steel-s remarkably. It provides a new way to fabricate Babbitt as bushing on steel substrate.

The purpose of this paper is to examine the tribological behavior of the synthetic chlorine‐ and fluorine‐containing silicon oil as an aerospace lubricant.

The chlorinated‐phenyl and methyl terminated silicone oil (CPSO), chlorinated‐phenyl and trifluorinated‐propyl with methyl terminated silicone oil (FCPSO) were prepared. Their physical properties such as saturated vapor pressure and the evaporation weight loss were evaluated. The tribological properties of the silicon oils under moderate load were investigated with an Optimol SRV oscillating friction and wear tester, as well as Four‐ball friction and wear tester according to the standard method of ASTM D 4172 under higher load. The elemental composition generated on steel ball surface were analyzed on a scanning electron microscope with a Kevex energy dispersive X‐ray analyzer attachment (SEM/EDS), and the chemical nature of elements on worn surface lubricated with FCPSO were studied by X‐ray photoelectron spectrometer (XPS).

It is found that the CPSO and FCPSO show good tribological behavior for steel/CuSn alloy tribological pairs and are superior to hosphazene (X‐1P) and perfluoropolyether in terms of friction‐reduction ability and anti‐wear performance. The anti‐wear performance of FCPSO as lubricants for steel‐steel contacts is superior to CPSO. The EDS results showed existence of F and Si on the worn surface with lubrication of FCPSO, while XPS results indicated the occurrence of tribochemical reaction of FCPSO with friction pair during sliding process with the formation of FeCl₂, FeF₂ and the absorption silicon oil films on the lubricated metal surface.

The results substantiate that chemical reactive elemental such as chlorine or fluorine, which is substituted into silicon oil, helps to improve the anti‐wear and load‐carrying capacity of the liquid lubricant. So the excellent thermal stability, low‐temperature fluidity, very low‐saturated vapor pressure and excellent lubricity for steel/CuSn alloy of the silicon oil of FCPSO and CPSO make it an attractive alternative to conventional liquid lubricant for space mechanism.

The study aims to the distribution rule of lubricating oil film of full ceramic ball bearing and improve its performance and life.

The paper established an analysis model based on the fluid–solid conjugate heat transfer theory for full ceramic ball bearings. The distribution of flow, temperature and pressure field of bearings under variable working conditions is analyzed. Meanwhile, the mathematical model of elastohydrodynamic lubrication (EHL) of full ceramic ball bearings is established. The numerical analysis is used to study the influence of variable working conditions on the lubricant film thickness and pressure distribution of bearings. The temperature rise test of full ceramic ball bearing under oil lubrication was carried out to verify the correctness of simulation results.

As the speed increased, the oil volume fraction in full ceramic ball bearing decreased and the surface pressure of rolling element increased. The temperature rise of full ceramic ball bearings increases with increasing speed and load. The lubricant film thickness of full ceramic ball bearing is positively correlated with speed and negatively correlated with load. The pressure of lubricating film is positively correlated with speed and load. The test shows that the higher inner ring speed and radial load, the higher the steady-state temperature rise of full ceramic ball bearing. The test results are in high agreement with simulation results.

Based on the fluid–solid conjugate heat transfer theory and combined with Reynolds equation, lubricating oil film thickness formula, viscosity temperature and viscosity pressure formula. The thermal analysis model and EHL mathematical model of ceramic ball bearings are established. The flow field, temperature field and pressure field distribution of the full ceramic ball bearing are determined. And the thickness and pressure distribution of lubricating oil film in the contact area of full ceramic ball bearing were determined.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2023-0126/

This study aims to characterize the composition of the tribo-layer formed during sliding of steel in the presence of crude jatropha oil (CJO) and epoxidized jatropha oil (EJO) under boundary lubricant application.

CJO was obtained from a local market and used as received. EJO was obtained by epoxidation process with peroxyformic acid catalyzed by acidic ion exchange resin. The tribological test was conducted by the four ball method according to ASTM 4192. Wear scars generated on the lower balls were used to characterize the tribo-layer. Energy-dispersive X-ray and X-ray photo spectroscopy analysis were conducted to characterize the tribo-layer composition.

EJO shows a lower friction coefficient compared to CJO. Moreover, EJO also shows better wear preventive properties compared to CJO. The oxidation of CJO and EJO has lead chemisorption of the oil to steel surface to cause formation of protective layers for the steel surface. The layers were constructed from inorganic oxide in the form of iron oxides and silicon oxide together with organic layers in form of aldehyde, ketone and carboxylic acid. The formation and removal of this layer from rubbing sites are considered to affect wear-preventive and friction behaviour of steel lubricated with CJO and EJO.

This works highlights friction and anti-wear characteristics of CJO and EJO. This work also presents the composition of the tribo-layer that formed because of the sliding of steel lubricated with CJO and EJO. The method and result can be used for further investigation and development of lubricant.

The author gives a review of developments over the past decade in new compositions and application practices for ball and roller bearing grease.