Experimental and Theoretical Investigations on Tool Wear and Surface Quality in Micro Milling of SiCp/Al Composites Under Dry and MQL Conditions

During the machining processes of ceramic particle reinforced metal matrix composites, the severe tool wear constrains the quality and cost of the parts. This paper presents the experimental and theoretical investigations of the tool wear behavior and surface quality when micro milling the 45vol% SiCp/Al composites under dry and minimum quantity lubrication (MQL) conditions. The results of scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) show that the wear mechanism of diamond coated micro mills are adhesive, abrasion, oxidization, chipping and tipping, even though it has been reported that abrasion is the most important tool wear mechanism when machining particle reinforced metal matrix composites. Compared with dry lubrication condition, the environmentally friendly MQL technique can enhance the tool life and surface roughness, and reduce the cutting force significantly under given cutting parameters. Then, finite element (FE) simulations are employed to investigate chip formation process in micro orthogonal cutting to reveal the effects of reinforced particle on tool wear and surface quality. The FE simulations shows the local high stress, hard reinforced particles in metal matrix, debonded and cracked particles are the key factors leading to the severe tool wear and the unsmoothed surface morphology.