Influence Of Surface Nanocrystallization/Nitriding Treatment On The Mechanism Fretting Wear Of TC4 Titanium Alloy

Due to its excellent performance,TC4 titanium alloys are widely used in the aerospace and biological fields of aviation.However,the lower hardness,poor wear resistance and higher fretting sensitivity of TC4 titanium alloy restrict its further application.In order to improve its resistance to fretting wear,some surface treatment technologies have received extensive attention,and the application of ultrasonic cold forging technology and plasma nitriding technology is the most widely.In this study,surface nanocrystallization?ultrasonic cold forging UCFT?/plasma nitriding compound technology was applied to strengthen TC4 titanium alloy:850?nitrided and UCFT+850?nitrided.Testing equipment were used to characterize the strengthened TC4 titanium alloy.The fretting wear properties and wear mechanism of TC4 titanium alloy by composite treatment were investigated by using the SRV-4fretting wear tester.The results are as follows:?1?The optimal nitriding temperature for nitridation of TC4 titanium alloy is850°C.At this temperature,the wear resistance of TC4 titanium alloy is optimal.After plasma nitriding,the hard nitride phase??-TiN and?-Ti₂N?formed on the surface of TC4 made the surface hardness increase obviously.With the increase of nitriding temperature,the content of nitrides increases,so the hardness increases and the thickness of the nitriding layer increases.The average friction coefficient and wear volume of the sample are the smallest and the wear resistance is optimal under 850°C.After the plasma nitriding,the formation of nitrided layer can effectively prevent the direct contact of metal and inhibit adhesive wear.?2?Different pairs of grinding balls have important influence on the tribological properties of composite treated specimens.The wear resistance of TC4 titanium alloy with nitriding and UCFT/plasma nitrided is better than that of the untreated sample?Different pairs of grinding pairs of Si₃N₄,6061Al,TC4?.The wear resistance of the UCFT+PN was the best,and the wear volume was about 1/8?Si₃N₄?,1/5?TC4?and1/4?6061Al?of the untreated sample.Comparing 3 different kinds of grinding balls?Si₃N₄,TC4 and 6061Al balls?,it is found that the higher the hardness of the grinding ball is,the greater the wear volume is,the more serious the wear is.?3?UCFT/plasma nitrided Compound Treatment Has Important Influence on Fretting Wear Performance of TC4 Titanium Alloy.The TC4 titanium alloy treated with UCFT/plasma nitrided was analyzed for its fretting wear performance.It was found that the anti-friction properties of the TC4 titanium alloy were superior to those of the untreated sample against the ball?Si₃N₄?.However,when the ball is TC4titanium alloy,the coefficient of friction of the nitrided and composite treated specimens is higher than that of the untreated specimen,and there is no effect of friction reduction.Tribological Wear Mechanism of TC4 Titanium Alloy under Different Treatments for Grinding of Ball Si₃N₄ and TC4 Titanium Alloys is taht:Under the low frictional load,the center of the wear marks of the sample is in an adhesive state,and the edge of the wear scar is in a part of the slip region.The slight abrasive wear and wear debris accumulation on the edge of the wear scar occur.