Effect Of Laser Shock Peening On Fretting Wear Properties Of Titanium Alloy

Titanium alloy is often used in the preparation of structural parts in aerospace field because of its excellent properties such as low density and high specific strength.The fretting wear of fastening parts,such as screw and tenon structure,leads to fatigue fracture,which seriously affects the safety performance of titanium alloy components.Surface modification and protection of titanium alloy has always been an important research direction.At present,laser shock strengthening technology as a new surface strengthening technology has been used to improve the fretting performance of titanium alloy in recent years.Previous studies mainly focused on the effect of laser shock peening(LSP)on fatigue properties,but rarely on the friction and wear of contact area.The wear of fretting contact interface has an important impact on fatigue properties.In this paper,the fretting wear behavior of titanium alloy under laser shock peening is studied,and the influence of laser shock peening technology on the surface integrity of titanium alloy is explored.The influence of laser shock peening on the fretting wear performance of titanium alloy under different displacement amplitudes is mainly analyzed,and the influence of laser shock parameters on the fretting wear characteristics is deeply analyzed.The surface integrity of titanium alloy is obviously changed by laser shock processing.The factors such as surface roughness,surface hardening layer,surface residual stress and grain refinement are introduced.With the increase of impact times,the surface hardness of titanium alloy increases from 324 HV to 403.6 HV and 440.2 HV,the surface residual stress increases to – 510 MPa and – 604 MPa,the depth of stress layer increases from 1.1 mm to 1.3 mm,the grain size is refined to a certain extent,and the surface roughness decreases from 0.165?m of the original material to 0.220 ?m and 0.344 ?m.With the increase of lap ratio,the roughness of titanium alloy is 0.367 ?m,0.344 ?m,0.283 ?m.The roughness decreases gradually.The effect of laser shock peening on wear properties is closely related to the displacement amplitude.When the displacement amplitude is small(25 ?m and 50 ?m),compared with the original sample,the friction coefficient of LSP titanium alloy increases obviously,the surface adhesion phenomenon intensifies,the adhesion layer is well preserved,the subsurface crack is not easy to expand,and the adhesion wear is serious.When the displacement amplitude is large,LSP treatment can reduce the friction coefficient,reduce the wear volume,reduce the slope of the spalling pit,inhibit the tendency of crack propagation,refine the abrasive particles at the edge of the wear scar,reduce the abrasive wear.The fretting wear properties of titanium alloy are greatly improved.Laser shock peening parameters(lap ratio,impact times)affect the fretting wear resistance.With the increase of impact times and lap ratio,the wear volume decreases and the fretting wear resistance improves.With the increase of laser shock peening impact times to two times,the delamination wear phenomenon in the central area of the wear scar is weakened or even disappeared,the debris size in the edge area is reduced,and the oxidation wear degree is aggravated,forming a dense third body layer to further protect the matrix,and the abrasive wear is weakened.With the increase of lap ratio,the delamination phenomenon of the material surface is slightly alleviated,and the fragmentation phenomenon of the surface compaction area is intensified.The difference of wear properties is closely related to the difference of surface integrity...