The tribological tests were performed using Nitinol 60 alloy pin sliding over GCr15 steel disc in the tribometer system. Four kinds of oils were experimentally investigated as lubrication oils for ...lubricating Nitinol 60 alloy in the boundary lubrication regime. The experimental results were compared with a reference dry friction. It was found that Nitinol 60 alloy can be lubricated significantly and has shown remarkable lubrication performance. A superlubricity behavior of Nitinol 60 alloy was observed under castor oil lubrication. An ultra-low coefficient of friction of Nitinol 60 alloy about 0.008 between Nitinol 60 alloy and GCr15 steel was obtained under castor oil lubrication condition after a running-in period. Accordingly, the present study is focused on the lubrication behaviors of castor oil as potential lubrication oil for Nitinol 60 alloy. In the presence of castor oil, coefficient of friction is kept at 0.008 at steady state, corresponding to so-called superlubricity regime (when sliding is then approaching pure rolling). The mechanism of superlubricity is attributed to the triboformed OH-terminated surfaces from friction-induced dissociation of castor oil and the boundary lubrication films formed on the contact surface due to high polarity and long chain of castor oil allowing strong interactions with the lubricated surfaces.
In the present work, the functionalisation of austenitic stainless steel, AISI 316L surfaces via nanosecond Nd:YAG laser texturing in order to modify the surface morphology with crosshatch and dimple ...patterns is presented. A tribological analysis under lubrication with sunflower and jojoba oil with and without the addition of a solid lubricant, MoS2 nanotubes, was performed. In conjunction with friction/wear response laser-textured surface wettability, oil spreadability and oil retention capacity were also analysed. It was shown that the crosshatch pattern generally exhibited lower friction than the dimple pattern, with the addition of MoS2 nanotubes not having any significant effect on the coefficient of friction under the investigated contact conditions. This was found in addition to the better oil spreadability and oil retention capacity results of the crosshatch-textured surface. Furthermore, texturing reduced the wear of the stainless-steel surfaces but led to an approximately one order of magnitude larger wear rate of the steel counter-body, primarily due to the presence of hard bulges around the textured patterns. Overall, the crosshatch pattern showed better oil retention capacity and lower friction in combination with different vegetable oils, thus making it a promising choice for improving tribological performance in various environmentally friendly applications.
This article aims to investigate tribological properties of a surface modified by laser texturing under full oil lubrication as well as the effect of laser texturing on the abrasion resistance ...properties. Laser texturing was carried out to fabricate a spherical bulge texture on the surface of GCr15 bearing steel using an SPI fiber laser. Rriction and wear tests were performed to simulate the actual situation of sliding friction under full oil lubrication. Mechanical properties of the micro bulge and substrate region were detected and analyzed using an optical microscope, microhardness tester, and residual stress detector. Friction and wear tests showed that under full oil lubrication, the friction coefficient (FC) of bulge-textured samples is positively correlated with texture density. Compared with a smooth sample, the FC of the sample with 50.2% texture density decreased by 64.4%. The sample with 28.2% texture density had a minimal wear volume (1.35 × 10
8
μm
3
), which was diminished by 87.6% versus the smooth sample. The microstructure of the heat-affected zone is transformed into austenite by a large amount of heat and finally became acicular martensite when cooled. The microhardness of the bulge was increased to 419 and 331% of that of the substrate in vertical and radial directions, respectively. In addition, the surface of the micro bulge mainly revealed 20-35 MPa of residual tensile stress. The research proved that the surface wear resistance and antifriction effect of the sliding friction pair can be greatly improved by laser texturing, which shows favorable prospects for engineering applications such as bearings, guide rails, and mold formation.
To expand the applications of MXene-Ti
3
C
2
in the field of oil lubrication, rounded groove surfaces filled with Sn-Ag-Cu-Ti
3
C
2
on CSS-42L bearing steel (RGSs-SACT-600) were prepared. ...Block-on-ring friction and vibration tests under oil lubrication were carried out. The results showed that the synergistic effects of Sn-Ag-Cu-Ti
3
C
2
and grooves improved the variation characteristics of friction forces and reduced friction and vibration on the surfaces. Sn-Ag-Cu-Ti
3
C
2
with excellent adsorption to lubricating oil suppressed the oil film rupture and improved the heat dissipation at the friction interface. The tribochemical reactions were induced by Sn-Ag-Cu and Sn-Ag-Cu-Ti
3
C
2
, improving the tribological properties on the worn surfaces. Under low speed and high load, RGSs-SACT-600 with uniform profiles had excellent bearing capacity and antifriction performance.
Laser surface texturing has proven beneficial in improving tribological performance in different lubrication regimes. However, the interaction between plateau roughness and surface texture remains to ...be further investigated, even though rough surfaces are common in engineering applications. In the present study, we investigated the frictional influence of surface texturing of ground surfaces under different lubrication conditions. Channel textures with different depths and area ratios were fabricated on ground surfaces, and their friction was tested in reciprocating tests. The experimental findings indicate that the textures caused increased friction for ground surfaces under boundary or mixed lubrication when the interface is well lubricated. Nevertheless, when the oil supply was limited, an up to 40% friction reduction was observed under test conditions.
To investigate the tribological performance of a copper alloy engine bearing under oil lubrication, seawater corrosion and dry sliding wear, three different PI/PAI/EP coatings consisting of 1.5 wt% ...Ce
O
, 2 wt% Ce
O
, 2.5 wt% Ce
O
were designed, respectively. These designed coatings were prepared on the surface of CuPb22Sn2.5 copper alloy using a liquid spraying process. The tribological properties of these coatings under different working conditions were tested. The results show that the hardness of the coating decreases gradually with the addition of Ce
O
, and the agglomeration of Ce
O
is the main reason for the decrease of hardness. The wear amount of the coating increases first and then decreases with the increase of Ce
O
content under dry sliding wear. The wear mechanism is abrasive wear under the condition of seawater. The wear resistance of the coating decreases with the increase of Ce
O
content. The wear resistance of the coating with 1.5 wt% Ce
O
is the best under-seawater corrosion. Although Ce
O
has corrosion resistance, the coating of 2.5 wt% Ce
O
has the worst wear resistance under seawater conditions due to severe wear caused by agglomeration. Under oil lubrication conditions, the frictional coefficient of the coating is stable. The lubricating oil film has a good lubrication and protection effect.
This experimental study investigates the friction and wear of three coatings commonly used in industrial applications, particularly in hydrodynamic bearings. The three materials under investigation ...were Babbitt, polyether ether ketone (PEEK) reinforced with 15% carbon fibers, and PEEK reinforced with 20% carbon fibers. The first polymer material was extruded, while the other was produced by fused deposition modelling (FDM). The materials were subjected to sliding tests in a pin-on-disc configuration, with a steel ball serving as the counter surface. The tests were conducted at room temperature, with a load of 10 N and under three different lubrication conditions: dry, grease, and oil. The linear speed was set at 0.3 m/s for the dry and semi-solid lubrication tests, while for the oil tests, the speed was set at 0.25 m/s. The greases used had consistency grades of NGLI 000 and NGLI 2. An ISO VG 68 circulation oil was used for the oil lubrication tests. Additionally, thermodynamic analyses were performed under the most severe conditions (i.e., dry) to investigate the steel-Babbitt and steel-PEEK contact.
Rolling bearings operating in harsh environments are extremely exposed to the risk of exogenous dust or wear debris particles, so there is a strong need to investigate the effects of particulate ...contamination on bearing operation and to identify problems early. The lubricated oil containing silica particles of various sizes and concentrations are prepared and introduced into thrust ball bearings to replicate the severe operating conditions. Vibration and acoustic emission (AE) signals were measured by accelerometer and AE sensor in a thrust ball bearing test rig. The experimental bearing raceway was observed by scanning electron microscope (SEM) and confocal laser scanning microscopy, and the evolution of the surface topography was analyzed to probe the wear mechanism. The results show that the most severe wear areas occur at the bottom of the bearing raceway, and its degree of wear is significantly influenced by the size and concentration of the silica particles. As the experimental time increases, the raceway surface undergoes an accelerated wear process originating from slight dimples, which leads to bearing failure. Furthermore, the introduction of particles into the lubricant increases surface root mean square (RMS) roughness, vibration and acoustic emission for different experimental durations. The vibration and AE signals are affected by a combination of solid particles and surface wear. The measured monitoring results can provide valuable information about the damage morphologies and subsequently about the state of the bearing during operation.
Surface texturing is one mechanism that friction coefficients in both dry and lubricated contacts can be reduced compared with untextured, flat surfaces. End milling and shot blasting are two ...processes used to produce surface textures, including monolithic textures that have one type of surface feature, as well as multi-scale roughness features when two texturing processes are sequentially used. In such surfaces, we have observed that surface texturing decreases the measured friction coefficient under lubricated conditions, and that greater reductions in the friction coefficient are observed for those surfaces that had been both end milled and shot blasted. Simulations replicating the experiments suggest that the greatest factor contributing to the reduced friction observed for the textured surfaces is a result of increased fluid pressure in the contact region resulting from cavitation of the lubricant. However, a substantial decrease in the depth of the dimples on worn surfaces was also observed, suggesting that entrapment of wear particles within the surface texture features may also influence the measured friction coefficient. Alongside friction measurements, analysis of the wear track depth showed that surface texturing also has a beneficial influence on the calculated Archard wear coefficient.
