Experimental studies of friction and wear on textured surfaces filled with composite solid lubricant and lubricated with grease were conducted on a sliding plain bearing to enhance the working performance and lifetime under different conditions. Circular microdimples of different diameters were fabricated on GCr15 bearing steel specimens using the semiconductor sound and light pumped Nd:YAG laser machining equipment. Ring-on-ring tribological test configuration with GCr15 tribopairs under a combined non-Newtonian lubrication of grease and composite lubricant was performed. The results showed that the surface textures on specimen GCr15 bearing steel material filled composite solid lubricant and lubricated with grease (TLG), reduced the friction by 27%, 46%, and 75% of the grease only (TG), solid lubricant only (TL), and nonlubricated (T) specimens, respectively. The textured specimen with dimple diameter of 109 μm lowered the maximum coefficient of friction by 38% and enhanced the antiwear properties of GCr15 bearing steel material remarkably. This indicated that grease has great potential in promoting service life and working performance of sliding plain bearing when combined with composite solid lubricant in a laser-textured surface. It is therefore beneficial for applications in the machinery and automotive components industries in saving energy and reducing CO₂ emission.

There is comprehensive work on the tribological properties and lubrication mechanisms of oil lubricant used on textured surfaces, however the use of grease lubrication on textured surfaces is rather new. This research article presents an experimental study of the frictional behaviours of grease lubricated sliding contact under mixed lubrication conditions. The influences of surface texture parameters on the frictional properties were investigated using a disc-on-ring tribometer. The results showed that the friction coefficient is largely dependent on texture parameters, with higher and lower texture density resulting in a higher friction coefficient at a fixed texture depth. The sample with texture density of 15% and texture depth of 19 μm exhibited the best friction properties in all experimental conditions because it can store more grease and trap wear debris. The reduction of friction is mainly attributable to the formation of a stable grease lubrication film composed of oil film, transfer film and deposited film, and the hydrodynamic pressure effect of the surface texture, which increases the mating gap and reduces the probability of asperity contact. This result will help in understanding the tribological behaviour of grease on a textured surface and in predicting the lubrication conditions of sliding bearings for better operation in any machinery.

Texture surface containing both micro-pits and a thin carbon coating was produced using laser surface texturing and magnetic-control vacuum sputtering. Tribological properties of the laser-textured surface coated with thin carbon were experimentally investigated at low-temperature (8–10 °C) under starved and lubricated conditions with a ring-on-ring test rig. The results indicated that the laser-textured surface combined with carbon coating (textured + coating) exhibited low wear intensity and friction coefficient under lubricated conditions, while moderate wear was observed under starved lubrication conditions as compared with the smooth, textured, and carbon-coated surfaces. The wear mechanisms of the lubricated, textured, coated surface under three working conditions (10 N and 1.25 m/s, 16 N and 0.25 m/s, and 50 N and 0.05 m/s) revealed plowing effect, corrosion, and adhesive wear, while oxidative and adhesive wears were observed under starved lubrication. Finally, the textured, coated surface was freely adaptable to different working conditions and exhibited additional effects for better tribological applications at low-temperature as compared with the smooth, laser-textured, and carbon-coated surfaces.

Ultrasonic motors are typically driven by the dry friction force between the rotor and the stator; the friction pairs’ high friction coefficient and low wear rate are two essential elements for improving the operational stability with longer service life. In this research article, high-precision microgroove arrays were manufactured on the surfaces of the stator and rotor of the TRUSM60 ultrasonic motor using laser machining. Dry friction and wear tests between the stator and the rotor were carried out with pin-on-disc using HSR-2M high-speed reciprocating friction and wear tester to determine the tribological properties of the ultrasonic motor. According to a different distribution of microgrooves on the two contact surfaces, the influence of smooth surface, single-sided texture, and double-sided texture on the friction pair's friction performance were discussed. The results show that the textured surface can substantially increase the coefficient of friction of the contact surface and reduce the rate of wear. The one-sided textured phosphor bronze surface with a microgroove width of 200μm and an area ratio of 20% had the highest coefficient of friction of 0.334 and a friction increase rate of 36.3%. Similarly, the single-sided textured Polyimide surface attained the highest friction coefficient of 0.355 and friction increase rate of 44.9% when the groove width is 150μm and the area ratio is 30%. A higher friction coefficient of the double-sided texture can be obtained through reasonable parameter configuration than the single-sided texture. The included angle of 0° between the two textured surfaces produced the highest friction coefficient of 0.368 and the wear rate of the phosphor bronze and polyimide surfaces were 2.01 × 10⁻⁴ mm³/N-m and 1.949 × 10⁻³ mm³/N-m, respectively. The result provides an essential benchmark for enhancing the tribological performance of ultrasonic motors and increasing the output torque.