A comparative study of the surface topography in dry and wet turning using the confocal and interferometric modes

Abstract

This article is concerned with dry and wet turning of C45 steel using sintered carbide tools. The study focused on the surface topography of workpieces obtained by means of a 3D surface measurement system operating in two modes: confocal and interferometric. The main purpose was to compare the corresponding data measured in the two modes, confocal and interferometric. The study also aimed to analyse the tool wear depending on the turning conditions. The use of a scanning electron microscope and a stereoscopic microscope was essential to comprehensively characterise the workpiece surfaces and determine the cutting tool wear. The results obtained in the confocal and interferometric modes differed. The confocal module proved to be better for characterising the surface topography of C45 steel machined by turning. The surface quality after wet turning was higher than after dry turning; hence the lower values of the 2D parameters (Ra, Rq, Rp and Rv) and of the 3D parameters (Sa, Sq, Sp, Sv). The wear visible on the cutting tool after wet turning was half as much as that after dry turning (e.g. surface abrasion indicator VBBmax equal to 0.21 mm for wet turning and 0.39 mm for dry turning). The results prove that the choice of methods for measuring the surface topography (by determining the relevant parameters and functions) and analysing the surface features can play an important role in the characterisation of the machined surface. A well-thought-out research methodology is thus essential. From the experimental data, it is also clear that the use of mineral oil-based cutting fluid for turning with sintered carbide tools improved the surface quality of workpieces and reduced the tool wear.