Effect of silicon content on PVD film mechanical properties and cutting performance of coated cemented carbide inserts

The paper investigates the effect of Si content on TiAlSiN, TiSiN and TiAlN/TiSiN films mechanical strength, brittleness, fatigue and adhesion. The films used were deposited on cemented carbide inserts by employing cathodic arc evaporation. For determining coating strength properties, nanoindentations were carried out. Based on the data acquired and a FEM continuous simulation of nanoindentation, elasto-plastic laws for the films were determined. The adhesion of the coatings was evaluated by inclined impact tests and by Rockwell indentations. The fatigue of the examined coatings, at ambient and elevated temperatures, was characterized via perpendicular impact tests. Moreover, nano-impact tests were conducted for capturing the influence of Si-content on film brittleness. The cutting performance of the coated cemented carbide inserts was tested in milling stainless steel 304 L at various cutting speeds. According to the obtained results, the beneficial effect of Si on the cutting performance of PVD coated tools was detected within an optimum cutting speed range. In addition, a superficial TiSiN layer on TiAlN coated cemented carbide tools leads to improved compound mechanical properties. These properties, as well as the cutting performance, depend on the TiSiN-film Si content and coating structure.