Effect Of Combined Treatment With Plasma Nitriding And Laser Surface Texturing On Microstructure And Vacuum Tribological Properties Of Titanium Alloy

With the continuous development of China's space industry such as “manned space flight” and “moon exploration project” and the continuous progress of space science and technology,higher requirements are put forward on the performance of spacecraft and aerospace materials.Due to the excellent properties such as low density,high strength,corrosion resistance,and low magnetic permeability,titanium alloy are increasingly used in aerospace equipment.However,the poor wear resistance of titanium alloys limits the wider application of titanium alloy fasteners.Therefore,aiming at the problem of poor wear resistance of titanium alloys,the purpose of this paper is to enhance the tribological properties of titanium alloys by surface-strengthening the titanium alloys by plasma nitriding techniques and laser surface texturing techniques.The plasma nitriding and laser surface texture combined treatment was carried out in this paper.We chose 5 different temperatures for plasma nitriding.And then the surface textures with different shape parameters were processed on the nitrided layer using laser.The surface morphology,microstructure,hardness,and phase composition of the reinforcement layer were analyzed using the three-dimensional white light appearance instrument,the scanning electron microscope,the microhardness tester,and the friction tester.Then,the tribological properties and the tribological mechanism of the reinforcement layer were investigated.The main result is as follows:(1)After the titanium alloy is treated by plasma nitriding,the nitriding layer formed on the surface obviously improves the microhardness of the titanium alloy surface,thus improving the wear resistance of the titanium alloy.However,nitrided layer will also increase the surface roughness of titanium alloy and increase the friction coefficient.And the hard nitriding layer at high nitriding temperature can produce hard abrasive debris and participate in the process of friction when the friction load is large.It will cause serious abrasive wear,thus affect the tribological properties of titanium alloys.(2)A dimple texture with a depth of about 30 ?m was prepared on the surface of the titanium alloy with laser.In the shape parameters of texture,the area ratio of texture has the greatest influence on the texture,and the wear volume of the titanium alloy after texturing decreases and then increases with the increase of texture area ratio.The texture can play a role in capturing and storing wear debris and reducing abrasive wear during the friction process,thereby providing a wear-reducing and wear-resisting effect.(3)After plasma nitriding and laser texturing,the hardness of the titanium alloy was significantly improved and the adhesive wear was reduced.At the same time,surface texture can store debris,reduce abrasive wear caused by hard debris produced in the process of friction,and reduce friction coefficient.Under the interaction of the nitrided layer and the surface texture,the tribological properties of the titanium alloy in both vacuum and atmospheric conditions have been significantly improved.