Study On The Fretting Wear Behavior Of TC4 Titanium Alloy After Shot Peening And Coating Treatment

Titanium alloy was widely used in aerospace and spaceflight structure because of its great comprehensive performance, however, as its resistance of fretting was weak, the life of titanium alloy in aviation structure decreased, hence, it is important to study on surface modification technology to improve its resistance of fretting. This paper manly studied three aspects:(1) the fretting wear behavior of TC4 titanium after shot peening; (2) the fretting wear behavior of TC4 titanium under different shot peening strength; (3) The fretting wear behavior under gross-slip of TC4 titanium alloy samples without shoot peening, single shot peening, and shot peening followed by plasma spraying of CuNiln coating. The results were as follows:Fretting map of operational states of TC4 titanium alloy has been changed when shot peening strength was 0.3 mmA, coverage was 200%. The fretting wear regime accessed to mix slip regime when the displacement amplitude was 50 ?m, two-body contacted and three-body contacted both existed. When the displacement amplitude increased to 100 ?m,150 ?m, The fretting wear regime accessed to slip regime, large number of wear debris was produced, contact manner was three-body contact, local area of wear scar compacted. Normal load and frequency had little influence on fretting wear.With the increasing of displacement amplitude, the fretting wear regime transformed from mix slip regime, wear volume became greater; with increasing of normal load, the area of hertz contact get bigger; the area of wear scar get bigger, leading greater wear volume; with the increasing of frequency, oxidation degree of wear debris was higher, the number of hard oxide particles reduced, wear debris compacted more easily, wear volume decreased.The trends of friction coefficient can be divided in three process when the fretting wear regime accessed slip regime:firstly, at the early stage of fretting wear, oxide film broken, two-body contacted was in a dominant position, the friction coefficient raised rapidly since the adhesive and plastic deformation of the contact surface; secondly, large number of wear debris was produced, two-body contacted transformed into three-body contacted, the friction coefficient fluctuated largely; lastly, wear debris generation balanced with overflowing, fretting wear was in a relatively stable state, the friction coefficient changed little. As Ar/N reduced with the increasing of normal load, and then, the friction coefficient reduced too.With the shot peening strength increased from 0.3 mmA to 0.5 mmA. The roughness and surface brittleness of TC4 titanium increased, the fretting wear regime transformed into slip regime. Oxidation degree of the center of wear scar was higher than the edge of wear scar always under different shot peening strength and fretting state. The wear volume of these specimen whose shot peening strength was 0.5 mmA was always greater than those specimen whose shot peening strength was 0.3 mmA.There was no complete formation of the third body layer of the TC4 titanium alloy which was unpeened, and some area were still two-body contacted. In the process of fretting wear, with the decreasing of the size of wear debris oxidation degree reduced and oxidation degree of the center of wear scar was higher than the edge of wear scar. The wear volume after shot peening increased, however, the combined treatment of shot peening followed by plasma spraying can reduce the wear volume.