Abstract
Die casting dies are exposed to an extreme erosive–corrosive environment during a typical die casting operation using aluminium alloys. The erosive actions are primarily due to the high velocity injection of the liquid melt through narrow gates. This molten spray of liquid droplets attacks surfaces in front of the gates and normal to the flow front and is called ‘washout’ by die casters. The corrosive action on the other hand is governed by the solubility of the die material (often H13) in the molten aluminium alloy and is controlled by the composition of the cast metal and the die steel, and causes ‘soldering’ in die casting. To protect die surfaces from these erosive–corrosive actions, surface treatments and thin film ceramic coatings applied by PVD and CVD techniques have been evaluated using both laboratory tests and production evaluation. This paper provides details of the coating candidates, the tests, and the analysis of coating failure. It presents the results of these tests and explains the mechanisms for erosive–corrosive failure of H13, and the PVD and CVD coatings in the die casting environment.
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