Effects of Laser Surface Texturing and Lubrication on the Vibrational and Tribological Performance of Sliding Contact

Various textures are fabricated by a picosecond laser machine on the surfaces of circular stainless steel specimens. Vibrational and tribological effects of laser surface textures are investigated by means of a tribometer and a data acquisition and signal processing (DASP) system. Experimental results show that surface textures can reduce the coefficients of friction (COFs), enhance the wear resistance, and improve the dynamical performance of frictional surfaces. In this study, the surface with micro circular dimples in diameter of 150 μm or textured area density of 25% has the best tribological and dynamical performance. Compared with the non-textured surface, the surface with circular dimples in diameter of 150 μm and 15% textured area density has 27% reduction of COFs, 95% reduction of frictional vibrations, and 66% reduction of frictional noise. The frictional vibrations and noise in the sliding contacts can be effectively reduced by adding graphene to the lubrication oil, and the surface textures enhance the frictional noise reduction performance of lubrication.

A Review on Friction Stir Processing Over Other Surface Modification Processing Techniques of Magnesium Alloys

An enormous amount of research is conducted on aluminium alloys on friction stir process, despite magnesium alloy reporting severe weight reduction when compared to aluminium alloys; a very slight amount of research was testified by friction stir processing of magnesium alloys. Magnesium is highly reactive and susceptible to corrosion in the presence of an aggressive environment. This highly corrosive nature of magnesium limits its applications. Surface properties like crystal structure, composition, and micro structure influence the corrosion and wear property of the material. Coating and alloying like laser surface modifications are performed to passivate magnesium surface from corrosion. Coating techniques, however were found to be insufficient in corrosion protection due to coating defects like pores, cracks, etc, and adhesion problems caused due to poor surface preparation of the substrate, and also impurities present in coating which provides micro galvanic cells for corrosion. Current study analyses the detailed overview of different types of Surface modification methods such as Physical vapor deposition, Chemical vapor deposition, Chemical conversion coating, Ion implantation coating techniques and also work focuses on few of Alloying or Surface processing methods such as Laser surface modification namely Laser surface melting, Laser surface cladding, Laser Shot Peening, Laser surface alloying and Friction stir processing (FSP). Friction stir processing a novel method derived from friction stir welding is used as surface modification method, which modifies micro structure, composition of surface layer without changing bulk properties, for enhancing corrosion resistance property. FSP enhances the micro structure and homogenizes but it is also eliminating the breaking up of the brittle- network phases and also cast micro structure imperfections. Indeed FSP can produce particle and fiber-reinforced magnesium-based surface composites. FSP empowers the manufacturing of magnesium by adding additives. Comparison of the different methods of coating and surface modification has been compared with FSP

A Novel Process for Manufacturing High-Friction Rings with a Closely Defined Coefficient of Static Friction (Relative Standard Deviation 3.5%) for Application in Ship Engine Components

In recent years, there has been an increased uptake for surface functionalization through the means of laser surface processing. The constant evolution of low-cost, easily automatable, and highly repeatable nanosecond fibre lasers has significantly aided this. In this paper, we present a laser surface-texturing technique to manufacture a surface with a tailored high static friction coefficient for application within driveshafts of large marine engines. The requirement in this application is not only a high friction coefficient, but a friction coefficient kept within a narrow range. This is obtained by using nanosecond-pulsed fibre lasers to generate a hexagonal pattern of craters on the surface. To provide a suitable friction coefficient, after laser processing the surface was hardened using a chromium-based hardening process, so that the textured surface would embed into its counterpart when the normal force was applied in the engine application. Using the combination of the laser texturing and surface hardening, it is possible to tailor the surface properties to achieve a static friction coefficient of ≥0.7 with ~3–4% relative standard deviation. The laser-textured and hardened parts were installed in driveshafts for ship testing. After successfully performing in 1500 h of operation, it is planned to adopt the solution into production.