Hard coatings produced by PACVD applied to aluminium die casting

The advantages of using different types of hard coatings in the field of aluminium die casting have been demonstrated in several publications. Hard coatings can protect the steel surface of casting tools from erosion of liquid aluminium and improve the resistance against thermal cracking. The coatings are also expected to prevent the aluminium from soldering onto the tool surface. Lifetime increases in cores and moulds are reported with coatings deposited by CVD, PVD and PACVD. PACVD offers the possibility to coat the tools at temperatures below their tempering temperature (in contrast to CVD), and there is no need to move the tools during the process or to adjust the target arrangement of the tools to coat uniformly as in PVD. Therefore, PACVD also seems to be a very promising method to coat larger moulds and offers new possibilities for the application of hard coatings in the aluminium die casting field. Within this work, different types of hard coatings produced by PACVD were tested in aluminium die casting applications: TiN, Ti(C,N), Ti(B,N) and (Ti,Al)(C,N). The films have been characterized with respect to their thickness, microhardness, adhesion, chemical composition, morphology and microstructure. The application of PACVD-coated cores showed a significant increase in lifetime, and for all coatings types, no tendency of soldering was found. Moulds with dimensions of 520 x 520 x 300 mm and a weight of approximately 200 kg were coated by PACVD and tested in applications.