WEAR RESISTANCE OF HARD COATINGS IN POWDER INJECTION MOLDING (PIM)

The degree of machine wear decisively determines the economic feasibility of powder injection molding. According to higher hardness of alumina powders (ca. 2000HV), manufacturing of ceramic components via PIM requires hard wear resistance equipments to overcome the wear phenomena. The wear test is based on the ASTM rubber wheel but the rubber wheel is replaced by a steel wheel of the same grade used in the barrel of an injection molding machine. The potential of hard coatings for wear protection in feedstock processing units is investigated in the present study. Model wear tests were carried out to demonstrate the tribological situation inside the screw/barrel system of extruders and injection molding machines. The substrate material was AISI 4140 steel which is used for PIM machine components. Hard coatings prepared by physical vapor deposition (PVD) and chemical vapour deposition (CVD) offer a good opportunity for wear protection. Due to higher temperature of feedstock and compression, the amount of wear in the metering zone is higher in comparison with other zones. The wear behavior also was strongly influenced by the characteristics of the feedstock (e.g. amount, size, shape and hardness of ceramic particles).