A Series of Test Shows the Impact of Carbon-Based Coatings in Aluminum Diecasting Operations.
Die castings produced with as-cast or nearly as-cast surfaces are becoming more common, where near-surface layers of the castings are machined. As a result, various problems related to the boundary between chill layers and general internal structures are more apparent. Controlling heat insulation during molten metal infusion, heat transfer during pressurization and thermal diffusion to the mold are critical to diecasting quality. Proper control of these variables will lead to dense cast structures free of chill boundaries.
In the paper “Key Issues for Quality Stabilization of Aluminum Die Castings,” Yuichi Furukawa, Toyota Motor Corp., Toyota, Japan, and Yoshiki Tsunekawa, Toyota Technical Institute, Nagoya, Japan, investigated aluminum diecasting processes. The report includes the results of a durability test of various carbon-based coatings, the effects on solidification structure and a coating’s ability to stabilize diecasting quality.
The typical microstructures of a diecast oil control valve (a) without carbon-fullerene coating and (b) with carbon-fullerene coating are shown.