Volume 39, No 2, 2017, Pages 145–151
Studies on Mechanical Behaviour of Aluminium/Nickel Coated Silicon Carbide Reinforced Functionally Graded Composite
A. Mohandas, N. Radhika*
The aim of the work is to fabricate functionally graded aluminium (Al-Si6Cu)/ nickel coated SiC metal matrix composite using centrifugal casting route. SiC particles (53-80 µm) were coated with nickel using electroless coating technique to enhance the wettability with aluminium matrix. Several attempts were made to coat nickel on SiC by varying the process temperature (65 °C, 75 °C, and 85 °C) to obtain a uniform coating. Silicon particles coated with nickel were characterised using EDS enabled Field Emission Scanning Electron Microscope and it was found that the maximum nickel coating on SiC occurred at a process temperature of 75°C. This nickel coated SiC particles were used as the reinforcement for the manufacture of functionally graded metal matrix composite and a cast specimen of dimensions 150×90×15 mm was obtained. To ensure the graded properties in the fabricated composites, microstructure (at a distance of 1, 7 and 14 mm) and hardness (at a distance of 1, 3, 7, 10 and 14 mm) from outer periphery taken in the radial direction was analysed using Zeiss Axiovert metallurgical microscope and Vickers micro hardness tester respectively. The microstructure reveals presence of more SiC particles at the outer periphery compared to inner periphery and the hardness test shows that the hardness also decreased from outer periphery (90 HV) to inner periphery (78 HV).Tensile strength of specimen from outer zone (1-7mm) and inner zone (8-14 mm) of casting was also tested and found out a value of 153.3 Mpa and 123.3 Mpa for the outer zone and inner zone respectively. An important observation made was that the outer periphery of casting was particle rich and the inner periphery was particle deficient because of centrifugal force and variation in density between aluminium matrix and reinforcement. Functionally graded Al/SiC metal matrix composite could be extensively used in automotive industry especially in the manufacture of liners and brake drums.
Liquid metallurgy, Electroless nickel coating, Scanning Electron Microscope, Centrifugal casting, Microstructure, Hardness