Research On High Temperature Friction And Wear Behavior Of TC11 Alloy By Laser Shock Peening

Laser shock peening(LSP)uses the laser induced high pressure and transient plasma shock wave to achieve material modification,which can effectively improve the wear resistance of metal materials.The tribological properties of laser shocked TC11 titanium alloy at different laser shock process parameters and environmental conditions were investigated.The morphologies,compositions and structures of worn surfaces and cross-section subfaces were observed and measured by using SEM and EDS,and the wear forms of TC11 alloys with LSP and without LSP was studied.The mechanism of LSP-improving the wear resistance of TC11 alloy under high temperatures was analyzed,which provides a theoretical foundation for the study of high temperature friction and wear properties of titanium alloys.The main conclusions are summarized as follows:(1)The laser shock processing parameters has a great influence on the friction performance of TC11 titanium alloy.The time of the friction coefficient achieving stable is shortened with the increase of laser impact pile numbers,and the friction coefficient of 50% overlap is bigger than 29.3%.The friction coefficient and its fluctuation of the LSP specimens decrease gradually with the increase of temperature.The friction coefficients of the laser shocked specimen and the non-laser shocked specimens increase gradually with the increase of the indenter loads.(2)LSP technology can significantly improve the wear resistance of TC11 titanium alloy.The wear resistance of titanium alloy improves with the increase of laser impact times.The wear resistance of the titanium alloy after LSP improves with the increase of the temperatures,while the wear resistance of the non-laser shock specimen increases at first and then decreases with the temperature increasing below 600°C.The wear rates of the TC11 titanium alloy specimens with LSP and without LSP increases with the increase of the loads,while the wear rate without LSP is larger below 25 N.(3)There are many cracks on the friction surface of the non-laser shocked specimen and the abrasive dust exhibits bulk spalling.The main wear mechanism of non-laser shocked is stripping wear,abrasive wear and oxidation wear,while the main wear mechanism after LSP is abrasive wear and oxidation wear under high temperatures.With the temperature increasing,the oxidation wear becomes more serious,but the material loss caused by the oxidation wear is much smaller than that caused by delamination wear.(4)The main mechanisms for the improvement of the wear resistance of TC11 after LSP are summarized as follows: a.The microstructure and hardness of the titanium alloy after LSP are in the gradient distribution.These layers have a good combination and uniform transition.b.After LSP,the surface layer of the titanium alloy is compressed,and the mechanical composite layer formed during the friction process is relatively dense.c.The LSP induced deep and high residual compressive stress in the titanium alloy can effective reduce the stripping wear by inhibiting the initiation and expansion of the cracks.