Abstract

Roller burnishing process is a superior cold forming finishing process. It is done on machine or ground surfaces for both external and internal surfaces. In this process, a smooth, hard object (under considerable pressure) rubs over the minute surface irregularities that are produced during machining or shearing. The hardened rolls of the tool press against the surface and deform the protrusions to a more nearly flat geometry. Since the surfaces are cold worked and in residual compression, they possess improved wear and fatigue resistance. The burnishing process is an attractive finishing technique which can increase the work-piece surface finish as well as micro-hardness in a single process, with reduction in tool set-up time which is difficult in conventional processes. The increase in the surface strength mainly serves to increase fatigue behaviour of work-piece under dynamic load. In this study surface roughness and micro-hardness are the main response variables and the process parameters under consideration are spindle speed, tool-feed, number of passes and lubricants. The material under consideration is En-8, which is commonly used industrial standard. Applying Taguchi’s design of experiments on the specimens, the aim is to find optimized values for enhancing the surface quality and hardness economically. The standard orthogonal array L-9 has been used. On experimental analysis, it is found that all the process parameters significantly affect the quality and in EN-8 the micro-hardness values are larger due to work-hardening effect. After the burnishing process no change in surface micro-structure was seen.

Key words: Roller burnishing, surface finish, micro-hardness, Taguchi techniques, micro-structure, optimization.