Fretting Wear Behavior Of Titanium Alloy-TA16

The damage failure of steam generator tube, one of the key equipments of nuclear reactor, has become a leading reason of the power stations'unplanned shutdown and the capacity factors'loss. Therefore, it serves as an essential index on estimating the reliability and economic factors of the reactor. This paper focuses on the fretting wear behavior of steam generator tube, choosing Titanium Alloy-TA16 materials as object of study. Experiments had been taken in different media environment by finite element analysis and simulation. The result can not only reveals the mechanism of Titanium Alloy-TA16 heat transfer tube, but also provides the key part of nuclear reactor with theoretical basis and guiding significance in order to prevent fretting wear. Based on the experiments and analyses, the following conclusions were obtained.1) Under the displacement amplitudes of 80-200μm, the fretting running curve of Titanium Alloy-TA16 steam generator tube materials obeyed the fretting maps theory, which was a parallelogram located in the slip region.2) In the atmospheric environment, there were four stages in the slip region. In the water medium environment, the friction changed gradually, with a relatively dramatic fluctuation in the stage when the grindings began to peel off. Overall, the rise of the displacement and the load was associated with the decline of the friction factor.3) During the wear process, the layer stripped and the tiny and grainy grindings attached to the surface of wear were mainly made up of oxide of titanium and titanium alloys. With the formation of the third body and material transfer, the friction oxidation was obvious. The third body consisted of the layer of plastic deformation and abrasive dust, reflecting the main features of wear mechanism, which could be characterized as adhesive wear, abrasive wear, the peeling off and rolling of abrasive grains, friction oxidation and the accumulation and transfer of grindings.4) Unlike the atmospheric environment, the time of the grindings'formation and peeling off reduced in the water medium environment while the displacement increased, which was accompanied with more damages of the steam generator tube materials. Micro-crack occurred on the surface of wear under long-term cyclic loading.5) The normal load, which caused the deformation of the steam generator tube materials, played a major role at the beginning of the damage by accelerating the whole process.6) During the collision procedure, the plastic flow of impact area material made the tube wall become local thinned and contributed to the later damage. The alternation of the maximum stress region between the internal and external tube wall could led to local fatigue. The damage of bend area was due to stress concentration. Collision was the chief reason of the steam generator tube materials'damage failure.