Investigation on Machinability and Damping Properties of Nickel–Phosphorus Coated Boring bar

Abstract

Chatter or self-excited vibration during machining process is always a serious problem which reduces intended dimensional accuracy. This investigation is mainly about reducing induced vibration through the electroless coating of nickel–phosphorus (Ni–P) on high carbon steel (EN 31) boring bar. The high carbon steel (EN31) substrate has been electroless coated with nickel–phosphorus at varying pH values (4, 5 and 6), and the damping effect of pH values on material deposition has been investigated. The coated substrate was subjected to heat treatment process and the influence of pH values and heat treatment process on structural stabilities of the coated specimens were analyzed using impact hammer test, and scanning electron microscope, energy-dispersive X-ray micro analysis and X-ray diffraction technique were used to study the structural changes in the Ni–P-coated boring bars. The pH values and heat treatment processes were found to play a significant role in improving the damping properties of the boring bars. The boring bar coated at 4 pH values resulted in better deposition of nickel and phosphorous over the substrate and offered better damping properties to the substrate. The heat treatment process on the coated specimen was found to render a crystalline structure to the substrate, thus offering improved damping proprieties to the materials.