Study On Torsional Fretting Corrosion Behaviors Of TI6AL4V And Cocrmo Alloys In The Serum Solution

Torsional fretting can be defined as a relative angular motion which is induced by reciprocating torsion in an oscillatory vibratory environment. As one of four basic motion modes of fretting wear, torsional fretting wear has been rarely studied up to now, especially under the condition of fretting corrosion. Therefore, this research has scientific significance to explore the unknown. At the same time, it will not only enrich and develop the basic theory of fretting tribology, but also has some practical reference values for understanding the failure mechanism of the artificial joints.In this paper, the counter-pairs of Ti6A14V flats verus ZrO2ball and CoCrMo flats verus CoCrMo ball were selected as the objects of study, and the torsional fretting corrosion tests were carried out in the serum solution. Based on the analyses of torsional dynamics and electrochemical corrosion behaviors and combined with surface profile-meter,3D surface profilometry, optical microscope (OM), scanning electron microscopy (SEM) and electron energy dispersive X-ray spectroscopy (EDX), and so on, the torsional fretting corrosion running and damage behaviors were investigated systematically. The main conclusions were obtained as follows:1. T-θ curves of Ti6A14V alloy in the pure water, serum solution and CoCrMo alloy in the serum solution appeared three basic shapes:linear, elliptical and parallelogram as the function of the increase of torsional angle displacement amplitude, corresponding to the partical slip regime, mixed regime and slip regime. Combining with OM morphology analyses of wear scars, the running condition fretting maps of Ti6A14V and CoCrMo alloys in the serum solution have been set up. Under the same normal load and tortional angle displacement amplitude, the extend of plastic deformation and damage for the Ti6A14V alloy in pure water were the most serious, and the CoCrMo alloy in the serum solution presented the slightest damage.2. Under the same normal load and tortional angluar displacement amplitude, the friction torque of Ti6A14V alloy in the pure water was topest, the next was Ti6A14V alloy in the serum solution, and the friction torque of CoCrMo alloy in the serum solution was the lowest.3. Under the same normal load and tortional angluar displacement amplitude, the corrosion potential negative shift and corrosion current of Ti6A14V alloy were higher than that of the CoCrMo alloy in the serum solution during the tortional fretting tests. As a result the electrochemical corrosion of Ti6A14V alloy was more serious relatively.4. In the partical slip regime, the damage mechanisms of Ti6A14V alloy in the pure water, serum solution and CoCrMo alloy in the serum solution were slight abrasive wear. In the mixed regime, the wear mechanisms of Ti6A14V alloy in the pure water were abrasive wear, delamiantion and slight oxidation wear; the wear mechanisms of Ti6A14V alloy in the serum solution were abrasive wear, delamiantion, certain oxidation wear accompanied with a little material transfer at the contact zone and electrochemical corrosion; the wear mechanisms of CoCrMo alloy in the serum solution were abrasive wear, delamiantion, certain oxidation wear zone, accompanied with a little material transfer at the contact and slight electrochemical corrosion at the same time. In the slip regime, the damage mechanisms of Ti6A14V alloy in the pure water were serious abrasive wear, oxidation wear and delamiantion, accompanied with some material transfer; the damage mechanisms of Ti6A14V alloy in the serum solution were serious abrasive wear, oxidation wear and delamiantion combined with some material transfer and serious electrochemical corrosion; the damage mechanisms of CoCrMo alloy in the serum solution were serious abrasive wear, oxidation wear and delamiantion accompanied with some material transfer and electrochemical corrosion.