Effect of film ion bombardment during the pvd process on the mechanical properties and cutting performance of TiAlN coated tools

Abstract

PVD process parameters, such as the deposition rate and duration, the bias voltage etc, affect significantly the film structure and strength properties and consequently the coated tool cutting performance. In the described investigations, cemented carbide inserts were coated with the same PVD nanocomposite TiAlN film in three individual processes, keeping all parameters constant and varying the substrates' positioning geometry as well as the deposition duration. In this way coated cutting inserts with various overall deposition durations and ions' bombardment durations, but with approximately the same film thickness were produced. The cutting performance of the coated inserts was investigated systematically in milling. The obtained results were explained by the FEM simulation of the cutting process, considering the mechanical and fatigue properties, as established by nanoindentations and impact tests respectively. The results revealed that at constant coating thickness, longer deposition duration and exposure time to ions' impacts lead to a densification of the growing film thus improving its yield, rapture and critical fatigue strength, resulting to a significant tool life increase in milling.