STRUCTURE OF COMPLEX COATINGS

Complex coatings for tools consist of (1) a tool substrate surface hardened by ion nitriding and (2) a thin hard coating deposited by the plasma vapour deposition (PVD) method (CAPDP, cathode arc plasma deposition process). The best practical effect is achieved only with the optimal coating structure which is determined by the predominant tool wear mechanism. The optimization of the coating structure can be achieved by varying the technological parameters during the hardening process. As a result coatings for tools were obtained with (1) tool life prolonged up to five or ten times and (2) metal cutting productivity increased two to four times. Thus, steel tools with complex coatings can be used instead of carbides (under certain cutting conditions).