Coated tools' performance in up and down milling stainless steel, explained by film mechanical and fatigue properties

Abstract

The knowledge of coated tool wear mechanisms in milling is crucial for explaining film failure and adjusting appropriately the cutting conditions. In the described research, coated cemented carbide inserts were applied in up- and down-milling stainless steel for monitoring the tool wear at repetitive cutting loads of various magnitudes and durations. The variable stress, strain and strain-rate fields developed in the tool during milling affect the film-substrate deformations, and thus the resulting cutting loads and the coating fatigue failure.For investigating the influence of cyclic impact load magnitude and duration on the film fatigue of coated specimens, an impact tester was employed which facilitates the modulation of the force signal. Using this device, repetitive impact loads with different duration and time profiles were applied on coated cutting inserts. These loads approximately simulate the developed ones in milling when the cutting edge penetrates the workpiece material. The attained coated tool life was associated with the developed maximum strain and its rate in the film during milling. The latter factors were correlated to the strain and strain rate dependent on coating fatigue endurance. In this way, the tool life in all examined milling kinematics and chip geometries was sufficiently explained.