New generation coatings for high speed cutting tools

CVD coatings have been traditionally used for enhancing the life of cemented carbide tools in machining operations. Due to several inherent advantages over CVD coatings, more recently the PVD coatings have been employed on cutting tools for improvement of their wear resistance and performance in machining operations. Significant variability in the tool life and performance of PVD coated tools has, however, been observed by several researchers. Such variability in tool life, which is a big hindrance in successful automation as well as planning of machining operations, is considered to result from a combination of factors including poor adhesion between substrate and coating, less than optimum design of coating architectures, increased diffusion wear at high temperatures and thermal softening of the hard coatings. This paper presents an investigation, which examines several novel architectures of PVD coatings for their suitability for high speed turning operations. Amongst the various coatings (TiN, TiC, TiCN and TilTiNffiCNffiC) investigated, TiC coating was observed to have the longest tool life and relatively better performance compared to the other coatings.