Wear resistant extruder screw

A wear resistant extruder screw for delivering polyvinyl chloride resinous material to an extruder, comprising:

• a nickel-based or iron-based alloy extruder screw body having a plurality of flights, a major outer diameter and an minor inner diameter, each of said flights having a pair of flight sides disposed between said major outer diameter and said minor inner diameter, said flight sides and said minor inner diameter defining a root area proximate to their juncture, said root area having a high propensity to undergo abrasive wear by said polyvinyl chloride resinous material;
• a metallic undercoating layer having a thickness of greater than 1 mil disposed over at least said root area, said undercoating layer having a coefficient of thermal expansion which is less than the coefficient of thermal expansion of said nickel-based or iron-based alloy extruder screw body;
• and
• a wear resistant coating layer having a thickness of at least about 10 mils disposed over said undercoating layer, said wear resistant coating layer having an ASTM G65 dry abrasion wear rating of less than 10 mm3/kilometer.