Plasma-enhanced, magnetron-sputtered deposition (PMD) of materials

Abstract

PMD combines conventional, balanced magnetron sputtering with an independently generated, arc-discharge plasma to deposit primarily TiN hard coatings for extending the wear life of gear cutting tools as used by General Motors Powertrain (GMPT). The work was begun in 1990 using end-mills coated in an 0.46-m diameter (18-inch diameter) chamber. This showed that the two tool-life controlling processes are deposition temperature and interfacial oxide concentration, control of which resulted in a 2–3× tool life over current commercial coating technologies. In 1994 scaling studies were begun using a 1.22-m diameter×2.44-m long (4-ft diameter×8-ft long) chamber to achieve this same level of performance for gear manufacturing tools such as hobs and shaper/cutters. Analytical modeling was used to correlate quantitatively the target poisoning and system stability with pumping speed, target power, gas throughout and fixture size for both chambers. The modeling was then extended to upscale the process to a 1.37-m diameter×1.52-m high (4.5-ft diameter×5-ft high) production prototype chamber with a 900-kg (2000-lb) capacity. This unit was incorporated into a production prototype facility in Michigan featuring tool degreasing and abrasive blast installations for surface preparation. The operating characteristics of the PMD process and the resulting cutting tool performance are presented.