Textured surfaces have been remarkable in improving the frictional performance of sliding contacts, particularly at instances such as boundary or mixed lubrication regimes. This article reports the results of an experimental and numerical study carried out by introducing surface textures in the form of protrusions to investigate its effects on friction performance under a mixed lubrication regime. The surface textures produced by the chemical etching process are tested on the pin on disc test rig by varying area density and height of the texture. In numerical simulation, the modified Reynolds equation (Patir–Cheng flow model) and asperity contact model (Greenwood–Tripp model) are solved for hydrodynamic and asperity pressures, respectively. The results indicate that the experimental measurements are qualitatively in good agreement with numerical predictions. Furthermore, the simulations are performed for different texture shapes by varying texture area density, height, and sliding velocity. The results depict that a maximum friction reduction of 87% with elliptical textures compared to the un-textured case.

A substantial increase in research activity on functionally graded materials (FGMs) was foreseen in the past few decades owing to their high strength and stiffness, design flexibility, and multi-functional features. However, the majority of the literature was confined to uni-directional (1D) gradation in material constituents. As a result, their usage was limited to a few advanced applications such as aircraft frames and shuttles, propulsion systems, and machine elements wherein the temperature is distributed along two or more directions. Thus, there is a demand for FGM that shows property variations in bi (2D) or tri (3D) directions. The present research work is an attempt made to design and develop bi-directional functionally graded material (2D FGM) with aluminum (Al) and copper particles. A 2D FGM sample in the form of a rectangular slab having material variation along x and y directions was produced through powder metallurgy using a 3D-printed cuboid. Variations in microstructure and hardness confirm the material gradation in two directions. Change in erosion wear at different locations was also observed on the sample. Furthermore, worn-out surfaces using scanning electron micrographs revealed a ductile fracture.

A five-layered aluminum–copper metal functionally graded material was developed through powder metallurgy process. The sample comprises different weight percentages of copper and aluminum that vary from 0 wt% to 100 wt % along the thickness direction. Erosion wear was performed on air jet erosion testing apparatus at a constant impact angle of 90o and impact velocity of 151 m/s. It was observed that erosion wear decreases when there is an increase in copper content. Layer 1 comprising 100 wt% of copper has shown 76.92% lower wear compared to layer 5 (100 wt% of aluminum). Besides, erosion resistance was enhanced at graded layers due to the formation of Al2Cu phase during sintering. Abrasive wear of metal functionally graded material was evaluated on the pin-on-disc test apparatus. Experiments were conducted at different loading conditions on various abrasive surfaces (P120, P800, and P2000). Irrespective of abrasive surface, the specific wear rate of aluminum–copper metal functionally graded material sample increased with an increase in load from 5N to 15N. At 5N, abrasive wear of metal functionally graded material on P2000 grit surface was 87.7% and 27.19% lower compared to P120 and P800, respectively. Eroded and worn-out surfaces were examined microscopically to understand the wear mechanisms and are discussed in detail.

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