This is a common concern among processors. We commissioned an ASTM G-77 test procedure to address this issue. In brief, tungsten carbide spinning against a bimetallic (FeB) liner shows no difference in liner wear than standard alloy materials such as Stellite and Colmonoy. Follow this link for more details (Adhesive Wear Test ASTM G77). A hard coated feedscrew contacting a less hard barrel liner is not a source of wear. In extrusion, system alignment, auxiliary die and barrel support, temperature profile, and proper screw design are much more critical to reducing wear.