Centrifugally Cast Metallurgical Coatings for Wear Resistance in Plastics Molding Machines

In extrusion and injection molding, centrifugally cast metallurgical coatings are often utilized to provide wear resistance in the barrel of the molding machine. The need for wear resistance is a result of two potential sources of wear, a screw or plunger that operates within the barrel, and the plastic being processed. Adhesive wear occurs under abnormal operating conditions when the screw bears against the barrel bore. Abrasive wear may result from certain additives used to modify the properties of the plastics. An in situ centrifugal casting process used for production of wear resistant coatings metallurgically bonded to the bores of heavy wall metal tubes is described. Characteristics of industry standard metallurgical coating alloys, a martensitic white iron, a Co-Ni-Cr-B alloy and a composite with tungsten carbide dispersed in a Ni-base alloy matrix are given. Metal-to-metal wear-compatibility tests are discussed.