Microstructure And Properties Of Fe-Cr-C Surfacing Alloys Reinforced With TiB₂and Nb

Fe-Cr-C surfacing alloy is an important kind of wear resistant material, which is widely used in metallurgy, mining, cement, construction machinery and other fields. By use of the Flux-cored wire, the chemical composition and microstructure of the surfacing alloys are easy to adjust. Hardfacing flux-core wire of Fe-Cr-C is widely used in welding repairment of such wear-resistant materials. In this experiment, self-made flux-cored wires of Fe-Cr-C have been used. By adding different amounts of TiB2, Nb, and adjusting the Cr/C radio, a variety of flux-cored wires were prepared. The hardfacing alloys were prepared by using arc welding on the surface of carbon steel Q235. The microstructures of Fe-Cr-C surfacing alloy were investigated by using optical microscopy, scanning electron microscopy and X-ray diffraction. The microhardness and resistance to abrasive wear of Fe-Cr-C surfacing alloys were tested by using Rockwell hardness tester, microhardness tester and abrasive wear tester. The influence of TiB2, Nb and Cr/C on the hardfacing alloys was investigated. In this way, the wear resistance of hardfacing alloys would be improved, and the most important guiding theory would be provided for the production of the flux-cored wire.The results showed that the microstructure of surfacing alloys was mainly composed of primary carbides, eutectic carbides, matrix and alloy carbides. The main phases of the hardfacing alloys are α-Fe, γ-Fe, TiC, NbC, Fe3C, M7C3, M6C23. With the addition of TiB2, a new hard-phase TiC can be abserved in the surfacing alloys, leading to the refinement of primary carbides. The carbides TiC lead to an increase in hardness and wear resistance.The grains were refined and residual austenitese were increased with the addition of TiB2and Nb. The effect of Nb on the hardness of hardfacing alloys was insignificant. The wear resistance has been improved by addition of Nb and TiB2. The wear resistance of the sample surfacing alloy with2%TiB2and5%Nb added is the highest.The higher the radio of Cr/C, the finer the primary carbides in the surfacing alloys are. The hardness and wear resistance of surfacing alloys with higher Cr/C radio is higher. In addition, the depleted zone of Cr is appeared in the microstructure of surfacing alloys with lower Cr/C ratio.