The effect of friction welding on the mechanical properties and corrosion fatigue resistance of titanium alloy drill pipe

Titanium alloys are the best candidates to replace steels for drill pipes in horizontal wells. However, friction welding (FW) may significantly change the properties of titanium alloy drill pipes. In this work, the microstructure, tensile and impact mechanical properties, and corrosion fatigue performance of the FW zone were compared with those of the base alloy. The results show that the base material is mainly composed of equiaxed globular α (hcp)-Ti, while the acicular α + β (bcc)-Ti is dominant in the FW zone. Due to these differences in microstructure, the FW zone has higher strength but lower stiffness and toughness than the base alloy. In addition, the fatigue performance and corrosion resistance of the material decrease in drilling fluid. These results indicate that FW zones in titanium alloy drill pipes might be the weakest region where crack, fracture, and corrosion are more likely to occur.