Architecture of PVD coatings for metalcutting applications: A review

The metalcutting process, which includes turning, milling, drilling, and other methods for shaping metals, generates large mechanical forces and high temperatures at the point of contact between the cutting tool and workpiece material. The cutting tool is damaged substantially in these severe service conditions and has to be replaced when the tool cannot produce the desired product at the specified tolerances. To improve the lifetime for which it functions properly, the cutting tool has to be protected, often by coatings that are specifically designed to prevent certain damage modes that occur in particular applications. In fact, over 90% of all cemented carbide inserts are currently coated using chemical vapor deposition, CVD, physical vapor deposition, PVD, or their combination. This paper will present PVD coatings that are specially designed to protect the cutting tool and extend its functionality (lifetime). The paper is organized in two parts. First, it will briefly describe the metalcutting process, the resulting challenges to the cutting edge and the components of a functional tool. The second and the main part will present and discuss the key PVD architectures employed to protect the tool: monolithic, multilayer and nanostructured coatings. The paper will conclude with a summary and outlook on the development of new PVD coatings for cutting tools.