Simulated Deep-sea Environment In Titanium Stress Corrosion

Titanium and titanium alloys in the marine environment has excellent corrosion resistance,which is widely used in shipbuilding, marine engineering and water work building.However, it is only superficial titanium alloy corrosion data of sea water that deep submergence vehicle and other structure design based on superficial seawater are lack of reliability data only. Therefore examining the deep sea environment titanium corrosion is very urgent, and titanium and titanium alloys as structural parts inevitably bear some stress, so that studing stress corrosion under conditions of deep sea is particularly important.In this paper, the corrosion sensitivity changes in seawater and 25MPa pressure of TA2,TC4 and Ti80 were studied through the slow strain rate experiments using elongation,reduction of area, stress corrosion sensitivity index as evaluation criteria , in addition fracture morphology and composition analysis were done through three-dimensional video, SEM and EDS analysis fracture morphology and composition analysis, examine changes in fracture mechanisms under different conditions. In addition, we are open-circuit potential and electrochemical impedance titanium and titanium alloy full immersion in salt water,alternating alternating wet and dry conditions and under pressure were detected, analyzed and evaluated, combined with mechanical properties testing, inspection alternating wet and dry and alternating pressure on stress corrosion susceptibility of titanium.Slow strain experiments under different conditions showed that: in atmospheric pressure or 25MPa pressure seawater environment, strain rate had no significant effect on the stress corrosion susceptibility. Under the same strain rate, TA2, TC4 and Ti80 stress corrosion sensitivity index increases in sequence, but all were less than 25%. It can be considered that there is no significant stress corrosion susceptibility.Immersion under different conditions showed that: in the first few days, the titanium was oxidized on the surface and the passivation film formed quickly with the film thickness increasing and denser. Stabilization of Three titanium passivation layer is as follows: Ti80>TC4> TA2. R (QR) Can be used to simulate the titanium surface after the passivation film was formed. The results showed that the fastest and the most stable film formation isunder the conditions of wet and dry alternating environment, ;and then is the condition of full immersion;the film is the thinnest and the most unstable under a constant strain rate . Slow strain test data indicated that stress corrosion sensitivity index was less than 25%, no stress corrosion tendencies existed.The Ti80 in seawater pressure alternating environment, there is no stress corrosion susceptibility. When strain is large, Ti80 surface passivation film forms slower, the trend of stress corrosion is larger. The form of tensile fracture is toughness cracking.