Experimental and numerical investigations on the machining performance of self-lubricant CrAlNAg coatings in dry turning operations

The influence of silver (Ag) alloying on the machining performance of CrAlN self-lubricating coatings was investigated during the dry turning of AISI 1045 medium carbon steel. Finite element (FE) simulations were conducted to predict the behaviour of the tools, focusing on the evaluation of the chip temperature and tool wear rate. The numerical results were subsequently validated by the experimental results. The outcomes revealed that the CrAlNAg coated S3 coating with an optimal Ag concentration achieved a balanced combination of hard nitride and soft phases, resulting in significant reductions in chip temperature, cutting forces, and machined surface roughness. However, excessive Ag content in the S4 and S5 tools showed premature tool wear, primarily due to the increased proportion of the soft phase, which deteriorates the coating´s mechanical properties. Conversely, the lower Ag content in the S2 coating diminished the effectiveness of the lubricant. These findings underscore the importance of optimising the Ag content to enhance the machining performance of CrAlN coatings.