Cailiao Baohu (May 2023)
Effect of Hydrofluoric Acid Concentration on Fatigue Behavior of Titanium Alloy Tubing
Abstract
In terms of the fatigue fracture problems of Zr-Mo titanium alloy (0.6Zr3Mo) oil well pipe caused by working environment during service, the fatigue properties of titanium alloy under different concentrations of hydrofluoric acid and laboratory conditions were investigated and compared by stress loading. Results showed that under the action of 70%σs stress amplitude, titanium alloys exhibited cyclic softening characteristics in both corrosive and non-corrosive environments. The hydrofluoric acid solution promoted the nucleation of fatigue cracks in titanium alloys and accelerated the propagation rate of fatigue cracks, which shortened the fatigue life of titanium alloys, and the fatigue life showed a decreasing trend with the increase of corrosion solution concentration. Meanwhile, the concentration of hydrofluoric acid had a certain impact on the crack propagation mode of titanium alloys, and in laboratory environments, the crack propagation of titanium alloys was mainly characterized by periodic cleavage. In low concentration hydrofluoric acid environments, secondary cracks formed by hydrofluoric acid corrosion could easily induce the formation of cleavage surfaces, and the crack propagation still propagated in a cleavage manner. In high concentration hydrofluoric acid environments, the propagation mode of cracks had changed with an increase in the degree of crack propagation in the ductile zone and a decrease in the degree of crack propagation in the form of cleavage.
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