Structure and Performance of Fe-Al Alloy Layer for Twin Wire Surfacing on the Steel Substrate

Abstract

Surfacing of Fe-Al alloy layer is achieved on the surface of Q235 steel plate by using the twin wire consisting of one aluminum welding wire and one steel welding wire in the shielding of pure argon. When the ER1100 aluminum welding wire of Φ1.6mm and ER50-6 steel welding wire of Φ1.2mm are selected as the master wire and slave wire respectively, with preheating and interlayer temperature reaching 350°C by controlling filling volume of aluminum and steel , the Fe-Al alloy layer featured by well-formed welding line is thus gained with no macroscopic defect. As the mechanical performance testing shows, the shear strength of surface combining surfacing layer and steel substrate is higher than 270MPa. The rupture position is located in surfacing layer and it turns out to be brittle fracture; the micro-hardness of surfacing layer ranges from 320HV to 420HV. Abrasion resistance testing indicates that abrasion resistance of surfacing layer is better than that of base material. According to micro-structure observation, the welding line is a coarsening columnar structure with a great deal of precipitated phase. According to EDAX, the aluminum content of precipitated phase in surfacing layer ranges from 24% to 32% (at), and the steel content ranging from 76% to 68% (at) - it is thus considered a Fe3Al structure through XRD.