High-temperature tribological behaviour and machining performance of self-lubricant CrAlNAg coatings for dry milling operations

Tribological and machining performance of CrAlNAg coatings having different Ag content tested against AISI 1045 medium carbon steel were assessed. Wear track was evaluated by scanning electron microscopy and energy dispersive spectroscopy. 3D topography of wear track and ball counterpart was determined by non-contact type profilometer. The formation of different oxide phases on track was confirmed using Raman spectroscopy. CrAlNAg9 and CrAlNAg12 coatings were found beneficial in reducing material adhesion from counterpart thus providing protective layers to counterpart, whereas small addition of Ag did not provide any improvement on CrAlN coating performance. CrAlNAg9 coated milling inserts demonstrated best results in terms of reduction in chip temperature (∼17.5 %), cutting forces, surface roughness (∼47 %) and chip thickness (∼12.7 %) compared to uncoated inserts.