Correlation of microstructure with the wear resistance and fracture toughness of hardfacing alloys reinforced with complex carbides

A correlation was made of the microstructure, wear resistance, and fracture toughness of hardfacing alloys reinforced with complex carbides. The hardf acing alloys were deposited twice on a low-carbon steel substrate by a subm erged are welding (SAW) method. In order to investigate the effect of compl ex carbides, different fractions of complex carbide powders included inside hardfacing electrodes were employed. Microstructural analysis of the hardf aced layer showed that cuboidal carbides, in which a TIC carbide core was e ncircled by a WC carbide, and rod-type carbides, in which W and Ti were mix ed, were homogeneously distributed in the bainitic matrix. In the surface l ayer hardfaced with FeWTiC powders, more complex carbides were formed, beca use of the efficient melting and solidification during hardfacing, than in the case of hardfacing with WTiC powders. As the volume fraction of complex carbides, particularly that of cuboidal carbides, increased, the hardness and wear resistance increased. In-situ observation of the fracture process showed that microcracks were initiated at complex carbides and that shear b ands were formed between them. leading to ductile fracture. The hardness, w ear resistance, and fracture toughness of the hardfacing alloys reinforced with complex carbides were improved in comparison with high-chromium white- iron hardfacing alloys, because of the homogeneous distribution of hard and fine complex carbides in the bainitic matrix.