Comparative analysis of wear on PVD TiN and (Ti1−x Alx)N coatings in machining process

Abstract

Ti3Al3N ternary coatings processed by Physical Vapor Deposition (PVD) are frequently used in machining inserts particularly for the automotive and aerospace industries. They possess many good qualities generally required in a cutting tool and high metal removal rates can be achieved with them. (Ti1−x Alx)N ternary coatings may form different crystalline structures (single cubic phase, mixed cubic and hexagonal phases, and single hexagonal phase) during processing, depending on the Al (at%) content. It is therefore important to study the relationship between the structures and properties of the coatings and their performance during machining under industrial cutting conditions. In the present work, the performance of carbide tools (ISO grade K10) with different (Ti1−x Alx)N coatings is investigated during continuous turning of nodular cast iron. Ternary coatings were processed by PVD in two ranges of stoichiometric ratios of Ti/Al, namely: (0.20≤x≤0.30) and (0.60≤x≤0.70). Machining trials using TiN coating were also performed for comparative analysis. Tool wear analysis was conducted within a Scanning Electron Microscope (SEM) and also using Energy Dispersive Spectroscopy (EDS). Statistical analysis of the results of a design of experiment test series indicated that the tools with low Al content coatings – (Ti0.71 Al0.29)N – exhibited superior performance in terms of wear rate and indentation test. However, tools coated with both low and high Al contents of (Ti1−x Alx)N presented higher wear rates than the TiN coated tools.