PVD COATINGS FOR DIE-CASTING MOLDS

In the field of non-ferrous diecasting, the tool life of the diecasting mould critically affects the cost effectiveness and quality standard of the foundry. It is therefore desirable to prolong the tool lives of diecasting moulds. The primary stresses to which the surface of the mould is exposed are thermal shock, abrasion and chemical reactions between the liquid aluminium and the iron in the steel mould. Certain regions of the mould are subjected to especially high stresses. In particular, these include ribs and the near-gate sections, where abrasion occurs owing to the high velocity of the melt. In the past a number of practice tests have been made with PVD-coated diecasting moulds. TiN was generally used as the protective coating material. These tests failed to achieve satisfactory results, i.e. the tool life was not significantly improved. The paper presents results obtained with Cr-based PVD coatings, which led to substantially increased tool lives.