Wear on the screw and barrel surface accompany polymer single screw plasticizing technology from the beginning. In general, the wear on the screws can be reduced by using nitrided steel surfaces, fused armour alloys on the screw flights and coatings. However, DLC-coatings (Diamond Like Carbon) combine a number of interesting properties such as a high hardness, a low coefficient of friction and an excellent corrosion resistance due to their amorphous structure. In this paper the wear resistance of about 50 µm thick DLC-coatings against polyamide 6.6, polybutylene terephthalate and polypropylene is investigated. The tribological situation in the solids conveying zone of a single screw extruder until the first point of melting is evaluated using a pin on disc tribometer and a so called screw tribometer. The polymeric pins are pressed against coated metal samples using the pin on disc tribometer and the tests are carried out at a defined normal force and sliding velocity. The screw tribometer is used to perform tribological experiments between polymer pellets and rotating coated metal shafts simulating the extruder screw even at higher pressure and temperature. Long term experiments were performed to evaluate the wear resistance of the DLC-coating. A reduction of the coefficient of friction can be observed after a frictional distance of about 20 kilometres using glass fibre reinforced polymeric materials. This reduction is independent on the polymer and accompanied by a black deposit layer on the wear surface of the polymeric pins. The DLC-coated metal samples show a 15 µm deep wear trace after the 100 kilometre test period against the glass fibre reinforced materials only. A tribological mechanism removing the interfacial layer between the DLC-coating and the polymeric material can be pointed out.