Influences of tribological and mechanical properties of (Ti /Al)N and diamond like carbon coated tungsten carbide tool on machining and dynamic stability in micro milling of Ti6Al4V

Abstract

In this article, the performances of thin-film PVD coated tools of similar chemical compositions such as TiAlN and TiN, and dissimilar chemical compositions like diamond like carbon (DLC) with respect to Ti6Al4V workpiece have been intended to analyze. The suitability of thin film coated tools for micro milling of Ti6Al4V is assessed by comparing machining responses such as cutting force, surface roughness, burr height, tool wear and dynamic stability. These are correlated with tribological properties of the coating and tool materials, which has not been reported yet for micro milling of Ti6Al4V. The value of coefficient of friction (COF) for coated and uncoated WC surfaces has been evaluated by considering Ti6Al4V as a counter surface. Among all coated and uncoated tools, the DLC coated surface gives the lowest value of COF which is 0.14. Adhesion is found as the major cause of higher COF of TiAlN coated surface (0.47) and TiN coated surface (0.44) as compared to the uncoated tungsten carbide (WC) surface (0.41). Among all the tools, the DLC coated tool manifested the best machining performance reducing percentage of diameter reduction, burr height, surface roughness, and cutting force by 30 %, 35 %, 17.5 % and 22.2 %, respectively, as compared to the uncoated WC Surface. Further, the critical stability limits of the uncoated and coated tools have been evaluated analytically through the dynamic stability analysis. The DLC coated tool exhibited the best dynamic stability performance enhancing the critical stability limit by 17.04 % compared to the uncoated tool.