Development of functionally graded composite for bearing applications

What is it about?

This study investigates the mechanical and tribological properties of a functionally graded Cu–Sn–Ni/ Al2O3 metal matrix composite, synthesized using horizontal centrifugal casting technique with dimension Φout100 × Φin85 × 100 mm. The microstructure was examined along radial distances at 1, 8, and 13 mm from outer periphery. Specimens were tested for tensile strength from outer (1–8 mm) and inner zone (9–15 mm) of the casting and fractured surfaces were subjected to fractographic analysis. Wear resistance of inner layer was experimented using pin-on-disc tribometer based on Taguchi’s L27 orthogonal array using three variable process parameters, such as applied loads (10, 20, and 30 N), sliding velocities (1, 2, and 3 m/s), and distances (500, 1000, and 1500 m). Optimum parameters were determined for wear rate on “smaller-the-better” basis using signal-to-noise ratio. Analysis of variance predicted the effect of each influential parameter and their interactions. Results depict that wear rate increased with load and distance, forming phases such as Cu3Sn, Ni3Sn, Cu6Sn5, etc. Worn surfaces analysis using scanning electron microscope predicted the formation of mechanically mixed layers, showing a V-trend influence of velocity on wear. Thus, fabricated composite shows the replaceability of conventional leaded bearing materials with superior copper functionally graded composites having better wear characteristics.

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Why is it important?

This investigation of tribological behavior can be effectively used for replacing the pre-existing materials for constant load bearings, subjected to cyclic loads especially in electric vehicle motors. The improved mechanical and tribological properties at the inner layer make it best suited for bearing application with prolonged life. It can also be utilized in different automobile components like cylinder liner and brake drum where tribological property of inner layer plays the major role.

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