Julius Caesar Puoza

Enhancing fuel efficiency and reducing exhaust emissions in internal combustion engines is vital for achieving carbon peaking and carbon neutrality targets. The cylinder liner–piston ring interface is a major contributor to engine friction, accounting for nearly 45% of total mechanical losses. Surface engineering technologies offer an effective pathway to reduce friction and wear at this interface, improving overall efficiency and supporting cleaner engine operation. This paper synthesizes key advancements in surface engineering for cylinder liner–piston ring systems, focusing on surface texturing, coating technologies, synergistic treatments, and material innovations. It reviews findings from finite element simulations and laboratory studies on how texture geometry, morphology, and distribution influence tribological behavior. The discussion covers a range of coating solutions, including wear‐resistant films, thermal barrier layers, metal matrix composites, diamond‐like carbon (DLC) coatings, nanocomposites, and ceramic coatings produced through advanced techniques such as atmospheric plasma spraying, high‐velocity oxygen fuel spraying, and laser cladding. The synergistic integration of surface texturing with coatings is examined to illustrate its combined effect on reducing friction and enhancing durability. The paper concludes by identifying current challenges in applying these technologies and outlining future research directions aimed at developing greener and more efficient internal combustion engines.

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.

The present study is directed to the thermal, mechanical, and microstructure fields in the MAG surfacing welding remanufacturing for a worn-out tunnel boring machine disc cutter. For this purpose, a numerical model is established for the surfacing welding process based on the theory of temperature field and thermo-elastoplastic deformation. The effectiveness of the proposed model was verified by a single-pass single-layer surfacing experiment of the H13 steel sheet sample. The numerical simulation results reveal that the surfacing process’s changing trend and stress distribution are complex, and the surfacing layer has to undergo stress formation and release. The residual deformation is mainly concentrated in the surfacing layer and deforms specifically along with its thickness. The experimental results showed consistency with the simulated result, and the hardness of the surfacing layer is about 1.5 times that of the base material. The surfacing layer mainly comprises eutectic carbides V₈C₇ and SiC, and the secondary carbides are Cr₂₃C₆ and Cr₇C₃. This article’s simulation results and experimental verification indicate that MAG surfacing welding is an effective method for the restoration (repair) of worn disc cutter. The remanufacturing process is technically sound and economically viable for tunnel construction.

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.

The advantages and disadvantages between ‘single pulse one time repeating at intervals’ (SPI) and ‘single pulse multiple times continuous’ laser micromachining technology on surface textures were experimentally investigated. The micromachining of 45 steel, GCr15 steel and grey cast iron materials were also studied using the interval manufacturing technology. The efficiency of the laser processing technologies and quality of the ablated micro-dimples such as the diameter and depth were systematically analysed. The experimental results showed that, the ‘single pulse one time repeating at intervals’ (SPI) micromachining technology produced high quality dimples with less heat affected zone, smooth dimples with little slags due to its ability to effectively alleviate the negative heat accumulation effect to produce quality dimples as compared to the ‘single pulse multiple times continuous’ micromachining technology process. The diameter and depth of the micro-dimples increased generally with an increase in the laser fluence for all materials. The grey cast iron has the smaller ablation threshold with the largest dimple geometry due to its high laser absorption rate and the presence of more sulfur (S) and phosphorus (P) in the chemical composition, while GCr15 steel exhibited the smaller geometry due to its hardness.

The core technique of electric storage water heaters is the manufacture of the tanks, and the welding technique is the key technology of the tank manufacture. A company producing water heaters received feedback from its after-sales that a large quantity of water leakage from the tanks was found in the market. A follow-up on the manufacturing site by the researchers showed that the position of the water leakage defects mostly happens in the welds of the tanks. Series of experiments were conducted to investigate the mechanical properties, residual stress, and diffusible hydrogen content of the longitudinal weld of the tank. Results of the mechanical properties showed that both the micro-hardness and the tensile strength of the welds are higher than the base metal. There are higher residual compressive stresses in the weld center and the adjacent-weld zone. Vertical residual compressive stress decreases first and then increases (149 MPa–28 MPa–134 MPa) from the weld ends to the middle, whilst the transversal stress decreases continuously (332 MPa~240 MPa) from the weld center to the heat affected zone. After enameling, the longitudinal welds’ peak micro-hardness of coarse grained region reduces by 30.9 HV1, and the average micro-hardness of the HAZ reduces by 5 HV1. The average vertical residual compressive stress difference of the same test points reduces from 270.6 MPa to 20.4 MPa. It proves that enameling can improve the mechanical property of the longitudinal welds.