Dual-rotary Fretting Wear Behavior And Characteristics Of Cocrmo Alloying In Three Different Conditions

While there usually being compounding fretting of two or more modes in industry, dual-rotary fretting, the one that takes place between two contacting surfaces as a torsional and relative movement under alternating loads and mirco amplitudes, is combined by torsional and rotational fretting. The phenomenon of dual-rotary fretting largely shortens the service life time of parts and components as affecting the security of producting, simultaneously, has been generating hugely economic loss. Moreover, the dual-rotary fretting widely exists in joint prosthesis planting, dental implanting, fracture fixating, etc. Nevertheless, it is rare to figure out the researchers that focus on this.This dissertation utilizing CoCrMo alloying ball and its flat specimen as the pair with the normal load of25N, tilt angle of10°and40°, and angular displacement amplitudes of0.25°,0.5°,1°,2°, the research on dual-rotary fretting was carried out under the friction environment of25%serum solution and artificial joint trophic liquid, while comparing with that in dry state. As testing the dynamic movement of the contact area in detail, it has discussed the running behavior and wear mechanism of CoCrMo alloy's dual-rotary fretting with the analysis of the scar in microcosmic with the aid of scanning electron microscope, optical microscopy, energy dispersive X-ray Dectector and profilometer. The results are as followed:1. It was available for the pair of CoCrMo alloying ball and flat specimen in serum solution, dry state and joint liquid to gain three basic types of friction-angular displacement amplitude curve, which appeared to be linear, elliptical and parallelogram-shaped.2. To found the Running Condition Fretting Map of CoCrMo alloy's dual-rotary fretting with the variable of tilt angle and angular displacement amplitude, we discovered it was prone for the contact pair to slip in serum solution and joint liquid rather than that in dry state.3. The frictional coefficients and dissipation energy of the CoCrMo alloy's fretting largely depended on the parameters of tilt angle, angular displacement amplitude and cycle numbers.4. The research showed that the wear behavior of CoCrMo alloying's dual-rotary fretting was strongly dependant on tilt angle, angular displacement amplitude and cycle numbers. As in serum solution,(1) While the fretting running in partial slip regime, the wear scar showed as annularity-shaped with center adhering and fringe micro-slipping, and there was little damage within contact center. The morphology of the scar appeared dissymmetrical, while the wear mechanisms in this case were mainly abrasive wear and slight oxidation wear.(2) In mixed regime, the adhesive state in scar's center has weakened that dedicated to the wear's intensification. Meanwhile, the relative movement between the contact surface transformed from the status of partial slip to that of gross slip with the increase of cycles, and at this moment, the wear mechanisms were still abrasive and oxidation.(3) As in slip regime, there happened severely plastic deformation among the whole contact area, and the wear was fierce while a large number of debris formed. In addition, the tilt angle obtained significant influence on debris'distribution, while the scar began to possess the characteristics of rotational fretting with the tilt angle's rising, and meanwhile the wear mechanisms were primarily oxidation, abrasive and a certain amount of stripping. While in artificial joint trophic liquid,(1) To run in partial slip regime, the wear scar showed as annularity-shaped with center adhering and fringe micro-slipping, and there was little damage within contact center, while the wear mechanisms in this case were mainly abrasive wear and slight oxidation wear.(2) In mixed regime, the wear became severer within the center, and the relative movement between the contact surface would have transformed from the status of partial slip to that of gross slip with the increase of cycles, and at this moment, the wear mechanisms were abrasive, oxidation and stripping.(3) As in slip regime, there happened severely plastic deformation with the formation of a large number of debris, while the wear debris particles have caused ploughing showed on the contacting surface. Furthermore, the tilt angle obtained significant influence on debris' distribution, while the scar began to possess the characteristics of rotational fretting with the tilt angle's rising, and meanwhile the wear mechanisms were the same as that in mixed regime.