Wear resistance of hard coatings in plastics processing

The degree of machine wear decisively determines the economic feasibility of plastics processing. The high temperature of plasticized material, high abrasion by fillers and corrosion attack will remain a problem. In addition, duality loss caused by wear products frequently becomes unacceptable and makes it necessary to shorten maintenance periods for replacing the worn components. The potential of hard coatings For wear protection in plastic 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 moulding machines. The test methods covered the solid and the molten stale of various moulding compounds. In comparison with standard metals used fur screws and barrels. the results show that. in general. hard coatings prepared by physical vapour deposition (PVD) and chemical vapour deposition (CVD) offer a good opportunity for wear protection: nut so much in the solids conveying zone bur more so in the melting zone. Furthermore. the results depict a dependence on the plasticized moulding compounds. (C) 1998 Elsevier Science S.A.