Performance evaluation of PVD coatings for high pressure die casting

During high-pressure die-casting (HPDC) of aluminium alloys, there is a ten dency for the molten alloy to react with the tool steel die, core pins and inserts. This occurrence within the high pressure die casting (HPDC) indust ry is referred to as 'soldering', It is of concern to high-pressure die cas ters because of crown-time due to the regular removal of the soldered layer and its detrimental affect on die life and casting quality. in this invest igation, several physical vapour deposited (PVD) coatings, namely, TiN, CrN and TiCN, were evaluated for their ability to eliminate soldering during H PDC of aluminium alloys. Accelerated semi-industrial trials were carried ou t in a 250-t Toshiba HPDC machine using a specially designed die made of P2 0 tool steel with removable core pins. The results from these trials showed that PVD coatings can act as a physical barrier coating preventing any rea ction between the molten aluminium alloy and the tool steel. Thus the probl em of soldering on such tools as core pins can be eliminated in high HPDC o f aluminium alloys. In the accelerated trials, it was found that soldering was replaced by a built-up layer of cast aluminium alloy, which was less de trimental to tool life and reduced machine down-time due to the reduced nee d for tool polishing. The experimental results were confirmed by conducting in-plant HPDC trials. (C) 2001 Elsevier Science B.V. All rights reserved.