An extruder barrel for twin screw extruders. The barrel body has a removable insert firmly seated in an insert receiving opening extending centrally and longitudinally therethrough. The insert has two circular bores with parallel axes extending centrally and longitudinally therethrough, the bores being in communication along a common chord. The walls of the bores have a wear and corrosion resistant layer that is a powder metallurgical material that is preferably applied by hot isotactic pressing. The preferred powder metallurgical material forming the wear resistant layer is a composition containing at least 50% by weight tungsten carbide with the remainder being nickel. The outer surface of the insert has a thin layer of a heat conductive, malleable material, such as copper, adhered thereto.