Alumina-mild steel friction welded at lower rotational speed

Abstract

The joining of ceramic-metal can be done using different techniques such as brazing, diffusion bonding, and friction welding. However, the mechanism of ceramic-metal joining has still not been fully understood. In this study, an alumina rod was bonded to a mild steel rod via the friction welding technique by using an Al 1100 sheet as an interlayer. The diameters of the rods were both 10 mm, respectively. A friction pressure of 20 MPa and a forging pressure of 40 MPa were used. Rotational speed was maintained at 900 rpm and friction times from 2 to 20 s were applied. The joining strength was determined through a four point bending test. The maximum bending strength, 240 MPa was obtained when the friction time of 20 s was used. Under optical microscope and scanning electron microscope observation, the bonding aluminum interface was clearly obtained. Mechanical interlocking and close contact between the alumina-aluminum and aluminum-mild steel were observed at magnifications of 3000×. The strength of alumina-steel bonding is much dependent on the wettability of the alumina surface by the partially molten aluminum interlayer and the existence of mechanical interlocking between the interlayer and mild steel.