Analysis of the performance of PVD AlTiN coating with five different Al/Ti ratios during the high-speed turning of stainless steel 304 under dry and wet cooling conditions

Abstract

High-speed machining of austenitic stainless steel normally causes significant tool damage and generates reduced tool life. In this paper, five AlTiN PVD coatings with different Al/Ti atomic ratios (50/50, 60/40, 67/33, 70/30 and 73/27) which deposited on cemented carbide inserts were used to conduct high-speed of 370 m/min finish turning tests. The experiments were carried out under different cooling conditions (dry and wet) on SS304 to study the tribological behavior of the AlTiN coatings with different Al/Ti ratios and the effect of the coolant under such aggressive cutting conditions. During the experiments, tool life, cutting force, wear mechanism, friction condition and surface integrity of machined workpiece were investigated. Crater wear was found to be the predominant wear mode during the cutting test, while the complex combination of oxidation, abrasion/attrition, adhesion, and chipping contributed to the tool failure. Given the machining conditions proposed in this study, the results revealed that all coated inserts possessed an improved friction behavior in the wet cutting condition. Compared to the dry machining, all five coatings had exhibited 2–3 times longer tool life. The AlTiN coated insert (Al/Ti = 60/40), in particular, exhibited a cutting length of almost 7000 m, compared to 1000 m for the AlTiN coated insert (Al/Ti = 73/27).