WEAR-RESISTANCE OF HARD COATINGS IN PLASTICS PROCESSING

The degree of machine wear decisively determines the economic feasibil ity of plastics processing. The high temperature of plasticized materi al, high abrasion by fillers and corrosion attack will remain a proble m. In addition, duality loss caused by wear products frequently become s unacceptable and makes it necessary to shorten maintenance periods f or replacing the worn components. The potential of hard coatings For w ear protection in plastic processing units is investigated in the pres ent study. Model wear tests were carried out to demonstrate the tribol ogical situation inside the screw!barrel system of extruders and injec tion moulding machines. The test methods covered the solid and the mol ten stale of various moulding compounds. In comparison with standard m etals used fur screws and barrels. the results show that. in general. hard coatings prepared by physical vapour deposition (PVD) and chemica l 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.