Investigations on the effect of thickness and structure of AlCr and AlTi based nitride coatings during hard machining process

In the present study, hard machining performance of Al2O3/TiCN based mixed ceramic insert was investigated as a function of thin film thickness. Aluminium rich mono-layered and multi-layered nitride coatings with similar mechanical and thermal properties deposited by physical vapor deposition (PVD) technique were considered with three different thin film thicknesses. The machining performance was evaluated mainly by power consumption, surface roughness, cutting temperature and chip reduction coefficient and correlated in terms of tool wear. Coating adhesion to the substrate increased with thickness for AlTiN coated tools whereas for AlCrN coating, 3 μm thin coating film exhibited best substrate adhesion which affected the machining behavior. Also, the multilayered structure of AlTiN coating outperformed AlCrN coating under good coating adhesion to the substrate. Cr-based nitride coating illustrated signs of flaking whereas Ti-based coating exhibited only abrasion wear at adverse cutting conditions.