Speaker
Description
To reduce the manufacturing time in turning parts with shallow superficial features like grooves of various geometries and short peripheral length, inserts with correspondingly shaped cutting edges may be used. Due to the short cutting time per part compared to the accumulative one associated with the overall tool life, turning process resembles interrupted cutting with alternative cutting loads. For avoiding the formation of cutting-edge fatigue cracks, cermet inserts of high ductility instead of cemented carbide may be applied. However, the high ductility reduces the mechanical properties of the cermet tools, thus, deteriorating their cutting performance.
A way to overcome this problem is to use ductile cermet cutting inserts coated with hard thin PVD films. In the described investigations, cermet inserts have been coated via a PVD HiPMS process with a TiAlN film of 3 μm thickness. These inserts were employed in turning hardened steel and their cutting performance was compared with that of uncoated cermet inserts of the same technical specifications. As expected, an improvement of the tool life was obtained when using the coated cermet inserts compared to uncoated ones. However, considering the current state of the art, this improvement is less than expected when using similar well adherent PVD coatings. This result was explained based on the cutting-edge loads developed in the coating and its substrate during turning, determined through appropriate FE calculations. Herein, the ductile cermet substrate is highly deformed, and the PVD coating is consequently overstressed during turning.
The substrate and coating material data applied in these calculations were defined with the aid of a FEM supported evaluation of related nanoindentation results. A significantly longer tool life was attained when reducing the substrate deformation, and thus the coating stresses as well, via replacing the cermet by convenient cemented carbide. Relevant analytical and experimental results are presented.
| Speaker Country | Greece |
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