ARC-DEPOSITED TI-ZR-N COATINGS ON CEMENTED CARBIDES FOR USE IN INTERRUPTED CUTTING

Hard coatings can significantly improve the performance of cemented carbide tools. In the case of carbides coated using chemical vapour deposition (CVD), however, a more or less pronounced loss of toughness is observable, restricting the range of applications, especially in interrupted cutting. This disadvantage can be overcome by using the physical vapour deposition (PVD) process. This paper uses the example of arc-deposited Ti-Zr-N coatings on cemented carbide indexable tips to illustrate the superior performance of PVD-coated as opposed to CVD-coated and uncoated cemented carbides in certain applications. The coating-substrate properties are related to coating parameters and film composition and correlated with tool lives in interrupted cutting. Coating parameters must evidently be selected to achieve a low process temperature and the most saturated stoichiometry possible. Ternary Ti-Zr-N coatings have some advantages over binary Ti-N or Zr-N films.