Industrial evaluation of duplex PVD hard coatings for HPDC

Abstract

© 2018, The Brazilian Society of Mechanical Sciences and Engineering. During high pressure die casting (HPDC), molten metal is injected into the tool cavity where it reaches high velocities that cause substantial wear of the tool components. In order to mitigate this problem, different surface treatments are sometimes employed for high production tools. The most common treatments are nitriding and physical vapor deposition (PVD) of hard coatings. Within this study, effectiveness of two duplex PVD hard coatings, CrN and TiAlN, was tested on core pins, which are the most endangered elements of high pressure die casting tools. Core pins were tested in four industrial production runs of an automotive component. In every run, the tool was mounted with one pin that was PVD-coated, and one that was gas-nitrided. Nitrided core pins were used as a base standard since the nitriding is the most commonly used surface treatment. TiAlN-coated pins were able to complete a full production run of 22,000 shots without significant damage. CrN coating showed somewhat higher soldering tendency and erosion rates. Considering that the untreated core pins were able to withstand only 5500 shots, it can be concluded that duplex PVD coatings can significantly improve tool lifetime. Additionally, results indicate that often disregarded variances in casting temperature or in cleanliness of ingots used in production can significantly influence wear performance of HPDC tools. Analysis of the production costs has shown that the application of duplex TiAlN coating on the core pins can lead to significant savings for tested automotive components.