Improvements in the thread cutting torque for a 6082-T6 aluminum-based alloy with tapping tools utilizing diamond coating

Abstract

The use of thin film diamond as a hard tool coating offers a significant wear protection in numerous machining operations and increases considerably tool's lifetime. The extreme hardness of the diamond is especially needed in machining highly abrasive materials such as aluminum-silicon alloys. Tapping is widely used for thread fabrication and it is often a time consuming process causing a delay on an automated production line. This study investigated diamond coatings in thread cutting and the aim was to gain knowledge about the performance of diamond-coated taps. PVD diamond coatings were deposited using ultra short pulsed laser deposition (USPLD) techniques. Another type of nanodiamond coating was a chrome-nanodiamond (CND) coating deposited by a two-phase electrochemical process to produce a metal matrix with embedded detonation nanodiamond (DND) particles. The main points were the analysis of tool torques of the thread machining data, sticking of aluminum alloy and wear behavior and mechanism of tested tapping tools. The tested tools were analyzed by Scanning Electron Microscopy (SEM) regarding tool wear and sticking of aluminum on tool surface caused by mechanical interaction. Coating approaches turned out to provide 13–30% improvements in cutting and 37–51% improvements in reversing for overall mean torques compared to uncoated reference tools.