Impacts of Surface Texture and Nature of Friction on Energy-Force Efficiency of Surface Plastic Deformation during Burnishing

Abstract

Burnishing, the plastic deformation of the workpiece surface due to sliding contact with a tool called burnisher, is a finishing operation widely used in various industries. In this work, impacts of the initial surface roughness Ra of the workpiece being burnished, the nature of friction in the contact zone, and the clamping force on the stability and energy efficiency of burnishing have been investigated. Experiments have been conducted with and without lubricant, represented by low-viscosity deep-hydrogenated fraction of sour oils, at initial surface roughness Ra of 0.8 and 1.25 μm and variable (100–200 N) clamping force. A key process indicator, which largely controls mechanics of burnishing, the temperature in the tool-workpiece contact zone has been measured using natural thermocouple method. Microhardness of the workpiece surface after burnishing has also been measured. It has been shown that changes in the temperature of the tool-workpiece contact zone are proportional to the changes in the squared tool clamping force. This dependence appeared to be universal and equally applicable to burnishing with and without lubrication. Based on the analysis of the experimental data, a new criterion of the burnishing efficiency has been developed. The new criterion simplifies the choice of optimum operational parameters and helps in preventing adverse impacts of structural phase transformations in the workpiece surface layer that unavoidably lead to reduced product quality and operational reliability and in reducing tool wear, which is critically important in the case of dry burnishing. The obtained results show that the nature of friction accompanying the surface plastic deformation has a significant impact on the stability and energy efficiency of the burnishing process. While the clamping force is equally important for burnishing with and without lubrication, the initial roughness Ra has an impact on dry burnishing only. Application of minimum quantity lubrication (MQL) under experimental conditions typical for industrial burnishing is found to be favorable. In particular, it was shown that MQL not only enhances the stability of burnishing process and but also increases its energy efficiency by more than 20%.