Effects of RE oxide on the microstructure of hardfacing metal of the large gear

The Rare Earth (RE) oxide was added into the electrode coating for hardfacing large gear and the microstructures of the hardfacing specimens with and without RE oxide were observed by using optical microscopy (OM). Meanwhile, the matrix phase of the hardfacing metals was determined by using X-ray diffraction (XRD) and the fractographs as well as inclusions were observed and analyzed by using scanning electron microscopy (SEM) with energy dispersive spectrum (EDS). The results show that, the microstructure of the hardfacing metal is mainly composed of the fine acicular ferrite, and the fracture surface is uniform and fine dimple exists on the fractograph of the specimen with RE oxide. The inclusions become spherical ones, which are distributed in hardfacing metal dispersively. However, the microstructure of the hardfacing metal is composed of coarse acicular ferrite and pearlite, and the fractograph is composed with dimple and quasi-cleavage in the specimen without RE oxide.