Evaluation of Mechanical Properties of TC4 Titanium Alloy Drill Pipe in Corrosive Environment

In order to study the adaptability of titanium alloy drill pipe materials to corrosive environments, according to corrosion requirements and test standards in NACE and GB, several processes were carried out. Firstly, some TC4 titanium alloy specimens were corroded and a comparison group without corrosion treatment was set. And then a series of tensile, impact and hardness tests were carried out to study its comprehensive mechanical properties under corrosive conditions. The results show that under the corrosion conditions of NaCl, H₂S, CO₂ and 205 ℃, the tensile properties of TC4 titanium alloy decrease by no more than 10%, the impact performance changes by only 0.33%，and the hardness decreases by 3.21%, indicating that TC4 titanium alloy possesses high corrosive resistance, can maintain better comprehensive mechanical properties under corrosive conditions. Taking the requirements of steel drill pipe materials in the API as an index, the mechanical properties of TC4 after corrosion treatment are shown as follows, yield strength, tensile strength and elongation are not lower than that of X grade steel, impact absorption energy is 62% higher than that of API requirement (20 ℃), the hardness exceeds that of G grade steel by about 37%, close to that of S grade steel. Therefore, TC4 titanium alloy can be used in corrosive well drill pipes to avoid or reduce the corrosion failure of the drill pipes.