Properties of Friction Welding Titanium-stainless Steel Joints with a Nickel Interlayer

Abstract

The probability and appropriate processing parameters of friction welding method of commercially pure titanium to a 304L stainless steel with an electroplated nickel interlayer have been investigated. The microstructure of the welded joints has been observed by optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy, and the main factors affecting friction welding process were analysed. Metallographic analysis revealed that a good bonding was obtained at both the titanium/nickel and nickel/stainless steel interfaces, and the diffusion products were identified in the weld zone. The effect of friction time and forging pressure on metallurgical and mechanical properties were evaluated. The results showed that atom diffused well and no presence of Fe–Ti intermetallic compounds appeared at optimum parameters. With the increment of friction time, the thermal degradation region increasing hence the thickness of interlayer material is decreasing. Microhardness test across the joining interfaces demonstrated the effect of solid solution hardening in the weld zone. The tensile strength increased with increasing forging pressure at constant friction time. Tensile test showed that the maximum average tensile strength of ∼289MPa was obtained for the joint welded at forging pressure of 320MPa. The tensile fracture surfaces are indicating river patterns of brittle mode of failure of the joints. The tensile fracture of the welded joint occurred in titanium side near the interface.