How the sub−surface microstructure of a Ti6Al4V tribopair evolves due to dry friction at high sliding velocity
Abstract
As part of aeronautical applications, friction experiments were performed between Ti6Al4V tribopair with a-equiaxed microstructure. Severe conditions were applied: less than 2 ms sliding at 40 m/s (apparent normal pressure of 110 MPa). Measurements and simulations indicated that the 25 μm of the top surface was heated in β for less than 1 ms and fast cooled. The microstructure in this thermally and mechanically affected zone was characterized by SEM, EDS and EBSD. Further Crossbeam microscopy was used to visualize the microstructure evolution through the affected layer. Far from the sliding surface, the microstructure showed prior equiaxed β grains fully transformed to martensite but also untransformed β phase. Closer to the contact surface, the grains were severely elongated along the sliding direction. Also 3D imaging emphasized non-expected recrystallized α grains near the contact interface. These observations were analyzed in detail to get new insight in the thermomechanical path undergone by the material top surface.