Preparation of in situ (Fe,Cr) 7 C 3 /Fe composite coating by centrifugal casting

Abstract

Using chromium wires as starting material, an iron based composite coating reinforced by in situ (Fe,Cr)₇C₃ particles, with a thickness of 4·0 mm, was fabricated on the surface of the ductile cast iron substrate, by means of a centrifugal casting technique. The microstructure and properties of the composite coating were investigated by optical microscope, X-ray diffraction, scanning electron micrograph, energy dispersive spectrum, microhardness tester and pin on disc wear tester. Results show that the composite coating consists of primary (Fe,Cr)₇C₃ carbides as the reinforcing phase and interdendritic (Fe,Cr)₇C₃/γ eutectics accompanied by negligible graphite nodules as the matrix. The composite coating is metallurgically bonded to the ductile cast iron substrate. Under the condition of dry sliding with loads, the composite coating offers virtually a unique wear resistant behaviour compared with that of unreinforced ductile cast iron material.