Hard coatings to prevent the washout phenomena in high pressure die casting tools

摘要

Hard thin coatings were deposited on a hot working tool steel to enhance its resistance to washout in high pressure die casting application. The washout is a complex phenomenon of degradation where erosion, soldering, corrosion usually occur jointly. All of these phenomena are major sources of limitation to the die service life. The application of hard PVD coatings may result efficiently against these degradation mechanisms when applied on particular parts of the die, e.g. the inlet and the pins. — A CrAlSiN coating system was deposited on the base material and different modulations of the chemical composition were developed to increase either the chromium or the aluminium-silicon content. — A set of coated specimens was directly analysed through optical and electronic microscopy, to assess their overall quality. Another set of specimens was subjected to cyclic immersions in a molten aluminium alloy bath. The washout signs were detected and monitored in function of the increasing number of cycles. The onset of soldering was mainly investigated through periodic electron microscopy inspections.