Correlation of microstructure with the wear resistance and fracture toughness of hardfacing alloys reinforced with compl
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I. INTRODUCTION
HARDFACING is a surface treatment method to improve the surface properties of metals, in which a welding metal that has excellent resistance to wear and oxidation is homogeneously deposited onto the surface of a substrate.[1,2] It is mainly applied to parts exposed to various wear environments, in order to protect them and extend their life. For example, when rolls need to be repaired due to damage during hot rolling of steels, hardfacing the roll surface makes considerable contributions in terms of lower material cost, higher productivity, improved product quality, and longer roll life. Alloys used for hardfacing are those of iron, nickel, copper, and cobalt. Among them, hypereutectic high-chromium white irons are most widely used in rolls, dies, and pressure containers as wear-resistant hardfacing alloys because of their excellent wear resistance and low cost.[1,5] Excellent wear resistance is associated with the presence of (Cr,Fe)7C3 carbides of 40 to 50 vol pct.[6] However, the application of these high-chromium white irons to wear-resistant parts exposed to heavy impact is limited, since they contain large and brittle chromium carbides. As carbides are separated or fall off from a matrix during the wear process, the resulting SEONG-HUN CHOO, formerly Research Assistant, Center for Advanced Aerospace Materials, Pohang University of Science and Technology, is Senior Researcher, Product Design Team, Samsung SDI Co., Ltd., Suwon, 442-743 Korea. CHANG KYU KIM and KWANGJUN EUH, Research Assistants, and SUNGHAK LEE, Professor, are with the Center for Advanced Aerospace Materials, Pohang University of Science and Technology, Pohang, 790-784 Korea. JAE-YOUNG JUNG, Senior Research Engineer, and SANGHO AHN, General Manager, are with the Materials and Processes Research Center, Research Institute of Industrial Science and Technology, Pohang, 790-330 Korea. Manuscript submitted February 28, 2000. METALLURGICAL AND MATERIALS TRANSACTIONS A
wear resistance can often be less satisfactory. Thus, another way to improve the wear resistance, together with fracture toughness, over that of high-chromium white-iron hardfacing alloys is to uniformly distribute carbides such as WC, TiC, VC, and Mo2C, which are harder but finer than chromium carbides, in a strong matrix. New hardfacing alloys reinforced with complex carbides, where hard and fine WC and TiC carbides are formed in a composite pattern, were fabricated in the present study. Electrodes made of FeWTiC and WTiC complex carbide powders, which have a much higher hardness than chromium carbides, were fabricated, and then hardfacing was conducted by submerged arc welding (SAW).[7,8] The microstructures of the hardfacing alloys were analyzed, and their hardness, wear resistance, and fracture toughness were evaluated. The evaluation data were compared with those of conventional high-chromium white-iron hardfacing alloys to define the mechanisms involved in the property improvement. II. EXPERIMENTAL A. Fabrication of Hardfacing Electrode The complex carbide powder
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