Effect of impact force on the impact-sliding wear of titanium alloy drill pipes against steel casings

Titanium alloys have been widely used for drill pipes in complex structural wells and ultra-deep wells because they can provide great benefits in cost and operation in drilling systems due to their excellent properties such as high strength, low density, exceptional corrosion resistance and inherent flexibility. However, their wear behaviors during drilling have not been well understood by the communities. In this work, the effect of the impact force on the wear performance of titanium alloy drill pipes against steel casings was investigated through using a modified wet impact-sliding pin-on-disc test system, in which ZSA-3 titanium alloy was used for the pins and J55 steel was for the discs. The tests were conducted under simulated drilling mud conditions. As the impact force increases, the coefficient of friction tends to become stable and fluctuates slightly, and thus the wear rate of the tribo-pairs decreases gradually. The wear mechanism of J55 steel discs presents a transition from plastic deformation to plastic deformation accompanied by adhesive wear, while that of the titanium alloy pins changes from the plowing effect with adhesive wear to plastic deformation and adhesive wear. In addition, complex oxides will be formed on the surfaces of the tribo-pairs due to the oxidation of Ti and Fe during the wear process. The present results could provide as a fundamental guide for the drilling engineers in related industries for reducing casing wear in the drilling environment.