The development of coating selection criteria to minimize die failure by soldering and erosion during aluminum high pressure die casting

NDC Neto, AL Korenyi-Both, C Vian, SP Midson… - Journal of Materials …, 2023 - Elsevier
NDC Neto, AL Korenyi-Both, C Vian, SP Midson, MJ Kaufman
Journal of Materials Processing Technology, 2023Elsevier
The steel dies used in aluminum high pressure die casting (HPDC) typically degrade and
fail due to the occurrence of different soldering mechanisms or to heat checking. Core pins
located directly in front of the gate are especially vulnerable to soldering and premature
failure. In this study, four sets of core pins were coated with different PVD/CVD coatings and
tested in a die used to produce a large automotive die casting. After production of thousands
of castings, the failure mechanisms of these core pins were identified as: mechanical …
Abstract
The steel dies used in aluminum high pressure die casting (HPDC) typically degrade and fail due to the occurrence of different soldering mechanisms or to heat checking. Core pins located directly in front of the gate are especially vulnerable to soldering and premature failure. In this study, four sets of core pins were coated with different PVD/CVD coatings and tested in a die used to produce a large automotive die casting. After production of thousands of castings, the failure mechanisms of these core pins were identified as: mechanical erosion, chemical soldering, gross chemical soldering, aluminum build-up on intact coatings, and coating spallation. The fraction of the core pin surface that suffered soldering was measured and correlated with coating wear resistance and coating wettability by liquid aluminum. These observations were used to establish criteria for coating selection aimed at minimizing failure of the die components by any of the observed mechanisms. These include: a maximum coefficient of friction (COF) of 0.40, a wear rate below 10−8 mm3N−1m−1, and a pin scar diameter ratio (Δd/D) below 0.22. Moreover, coatings that exhibit the lowest wetting angles (low cos(ϴ)) by liquid aluminum tended to minimize the chemical and mechanical degradation that led to soldering. This is the first time that numerical criterion have been developed in an attempt to guide coating selection for aluminum HPDC dies and the results sheds light on possible approaches for extending die component life in aluminum die casting.
Elsevier
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