Effect of CRYO-MQL on the surface integrity characteristics of machined Vanadis8 tool steel

Abstract

The machining industry is on the verge of transitioning from conventional to more sustainable practices. Different techniques of lubrication are one area of research that is evidently developing new practices to incorporate less waste while improving the tool life and performance of the workpiece. This research study compares surface integrity characteristics by machining the workpieces with alternative lubrication techniques, i.e., dry, emulsion, and minimum quantity lubrication. Residual stresses are measured by X-ray diffraction, and surface roughness is measured by optical profilometry to identify surface integrity parameters of the machined work pieces. This study expands the application of minimum quantity lubrication (MQL) by replacing the currently used aerosol mixture with cryogenic liquid nitrogen (CRYO) to reduce the heat generated at the cutting edge of the tool during the machining process. An experimental setup was utilised to conduct the necessary analysis for this research study. A new MQL setup was used to replace aerosol with liquid nitrogen. To analyse residual stress, the workpieces were etched to generate depth profiles, enabling the measure of the residual stress on the surface and underneath the top surface. Further, the same workpieces were used to measure the surface roughness in an optical profilometer. The temperature of the Cryogenic atmosphere at the tool and the cutting speeds were optimized by a test matrix, and these parameters were utilized throughout this research. The optimal cutting speeds (Vc) used were 50, 100, and 150 m/min, with a constant feed rate (f) of 0.15 mm/rev and the depth of cut (Ap) was 0.15 mm. Vanadis8 was the raw material, which was further heat-treated and used as the workpiece material. Turning operations were performed on the workpiece with varied lubrication techniques. The dynamometers were mounted on the tool holders during turning operations to measure the feed, cutting, and passive forces. The experiments were repeated for the second time to validate the residual stress and surface roughness measurements on the workpieces with the same parameters and experimental setup. The findings from residual stress and surface roughness measurements based on the cutting parameters with dry, emulsion and CRYO-MQL techniques are discussed in this research project.