On the properties of PVD coating based on nanodiamond and molybdenum disulfide nanolayers and its efficiency when drilling of aluminum alloy

Abstract

PVD coatings, based on nano-diamond (ND) and molybdenum disulfide nano-layers are tested and the results are presented in this paper. The best coating is built of 40 repeated functional blocks, where each block contains four alternating 10nm thick layers consisting of Cr+5% ND, Cr, Cr+MoS2 and Cr. It was determined from friction tests that the optimal total thickness is 40 blocks. The AlSi9Cu3(Fe) aluminum alloy was used as the testing material. The HS6-5 steel twist drills of 6.0mm in diameter were used, with and without protective coatings, at the cutting speed of 75.3m/min and the feed rate of 0.06mm/rev.Large burrs were formed when uncoated drills were used. In the case of using coated drills the vast majority of holes did not show any burrs or the sizes of the burrs were considerably smaller. The number of holes with burrs increased slightly with the drilling time. The built-up edges were formed along the major cutting edges of the drill. The intensity of built-up formation varied and depended on the drills used: the uncoated drills have built-up edges to a significantly greater height than the drills with the coating. Pickups are formed at the area of the drill chisel edge and at drill flutes and pickup sizes are more significant for the uncoated drills. The VB value of the flank surface wear for the uncoated drill was significantly higher as compared to the coated drill. The tool life of coated drill was found to be approximately 2.5 times longer in comparison with the uncoated drill.