Antifriction And Antiwear Mechanism Of Titanium Alloy By Laser Shock Texturing

Titanium alloy Ti13Nb13 Zr is widely used in medical metal materials,but the wear resistance of titanium alloy itself is poor,Laser shock texturing technology can improve the friction properties of titanium alloy surface.In this paper,taking the titanium alloy Ti13Nb13 Zr as the research object,the friction reducing and antiwear mechanism of titanium alloy Ti13Nb13 Zr by laser shock texturing was systematically studied.The main research works are as follows:(1)The frictional coefficient of the initial stage is divided into stages,The influence of laser shock textured on friction coefficient was studied.The results show that in the three stages of the initial friction process,the main factors affecting the friction coefficient in each stage were different.In stage I,the main factors were the running-in action of the asperities;In stage ?,the main factors were the abrasive particle collecting of micro dimple;In stage ?,the main factors were the �secondary micro dimple action�.These factors may not only play a role in a certain stage,but also accompany the whole process of friction and wear,such as the "secondary micro dimple action" in stage III,with the beginning of the friction experiment until the laser shock strengthened layer is completely worn out.(2)The influence of laser shock process parameters on friction coefficient in each stage of initial friction order process were analyzed systematically.The results show that the laser energy has great influence on the friction coefficient in the ? and ? stages.The different laser energy results in the change of the volume of the micro dimple and volume change of debris collected.The dimple spacing has a great influence on the friction coefficient in the ? stage.Different dimple spacing results in different number of micro dimple in the same textured area,resulting in different " secondary micro dimple action ".The micro dimple dislocation has a great influence on the friction coefficient in the ? stage.The different micro dimple dislocations lead to different ways for debris to enter the micro dimple,and the final friction coefficient changes.(3)In the process of stabilizing friction,the effects of laser shock process parameters and friction and wear conditions on friction coefficient were systematically analyzed.The results show that in the range of experimental parameters,the increase of energy leads to the increase of laser shock affected layer depth and hardness,So the friction coefficient decreases.The increase of dimple spacing leads to the decrease of the number of secondary micro dimple,the increase of wear debris leads to the aggravation of abrasive wear and the increase of friction coefficient.The existence of dislocations makes the �secondary micro dimple� have dislocations as well.The abrasive particles are easy to enter the micro dimple,and the friction coefficient decreases.With the increase of load,the newly formed �secondary micro dimple� is more likely to break down.The increase of temperature between friction pairs results in the softening of surface materials,the decrease of shear stress at interface and the decrease of friction coefficient.The higher the rotational speed,the higher the frequency of the cyclic stress on the friction surface,which will eventually lead to the generation of the friction surface cracks and the increase of the friction coefficient.(4)The distribution of stress and temperature field in the friction and wear process of laser shock textured and untextured specimens was studied.The results show that the micro dimple in the textured sample make the stress distribution uniform and the stress concentration degree alleviated;The micro dimple in the textured sample make the rising temperature smaller than that of the untextured sample,the temperature rising area smaller than that of the untextured sample,and the temperature distribution is improved.(5)The effect of microstructure and mechanical properties of titanium alloy on wear resistance was studied.The results are as follows: After laser shock,the grain size of titanium alloy is refined,the dislocation density is increased,and the total grain interface area is increased,which effectively inhibits the initiation and propagation of cracks.After laser shock hardening,the nano-hardness of titanium alloy surface is improved,and the residual stress is introduced into the laser shock affected area.which improves the wear resistance of laser shock textured titanium alloy surface.