| Abstrakt: |
Aluminium alloys are widely used in the various applications due to its favourable mechanical characteristics such as light weight, high strength, low density and high thermal conductivity etc. As its admirable properties, automobile, aircraft, defence and marine industries uses the aluminium alloy for replacing heavy weight materials. Eventhough, it offered acceptable mechanical characteristics, due to its poor tribological properties it cannot be applied in the high load sliding applications. Hence, it is necessary to modify the aluminium surface with suitable coating materials. In this investigation, an endeavour has been made to fabricate flyash-copper composite coating on AA7075 aluminium alloy using electrical discharge coating (EDC). Different coating parameters such as discharge current, pulse on time and pulse off time have been varied during EDC. Face centered central composite design in response surface methodology (RSM) is applied to conduct the EDC experiments. Response considered for this investigation are deposition rate (DR) and microhardness (MH). From the results, it was concluded that the deposition rate and microhardness increased with increasing of current and pulse on time and pulse off time. Highest microhardness value was obtained at the surface coated with higher current (8A) and pulse on time (80 µs). At the lower current (4A) and pulse on time (60 µs), cracks and small globules were identified, this could be due to the insufficient spark energy. Shallow craters were observed at higher pulse on time (80 µs) due to accumulation of melted particles resulted poorer surface finish. From the optimization, it was observed that the maximum DR of 0.3121and MH of 212. 1784 were obtained in the parametric conditions of 8A, 80 µs and 8 µs. [ABSTRACT FROM AUTHOR] |
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