| Weak anti-abrasion property of titanium alloys can bring about early fracture of compressor blade tenon made from titanium alloys during working process because of fretting wear,The fretting wear has become one of the main factors which affect the safe application of titanium alloys at room temperature and elevated temperature in nuclear power and aviation engine.It is important to improve fretting wear resistance of titanium alloy in aeronautic industry and other fields. However due to the complexity of fretting wear loading,fretting wear mechanism is still not quite clear.In addition,investigations of fretting wear tests have different methods.There is important theory significance to study the elevated temperature for the investigation of fretting wear mechanism and operating mechanism.Elevated temperature fretting wear behavior of TiAlZr titanium alloy substrate and its Chemical Vapor Deposition(PCVD) TiN/TiN+Si/TiN multi-layer coatings had been studied systematically using the elevated precision fretting wear apparatus.Their structure and element concentration were analyzed by X-ray Diffraction(XRD) and Energy Dispersion Spectrometer(EDS)respectively.The wear loss had been determined by means of Laser Confocal Scanning Microscopy (LCSM),Ambios XP-2 steps instrument,and the wear scar were observed by Optical Microscope(OM)and Scanning Electron Microscope(SEM).The fretting map on PCVD TiN/TiN+Si/TiN multi-layer coatings at different temperature had been built up. Furthermore,the effects of displacement,normal load and temperature on fretting wear had been focused on,and the mechanism of elevated temperature fretting wear was explored.Main conclusions were drawn as follows:(1)Fretting running rule of PCVD TiN/TiN+Si/TiN multi-layer coatings obey the fretting maps theory under different temperatures. Fretting running regimes of PCVD TiN/TiN+Si/TiN multi-layer coatings are made up of partial slip regime,mixed regime and slip regime.In the partial slip regime temperature has little influence on the friction coefficient,and in the slip regime the friction coefficient at 200℃is at the most.The trend of friction coefficient in different temperature is different.The wear volume became bigger follow the high of the temperature.The wear mechanisms of TiN/TiN+Si/TiN multi-layer coatings are abrasive wear and delamination at room temperature and 200℃,while at 400℃the mechanisms transform to delamination and oxidation wear.(2)Temperature has a special influence on the fretting wear behavior.When the fretting of TiAlZr titanium alloy is running in the partial slip regime,the wear is slight.When the fretting of TiAlZr titanium alloy is running in the mixed regime,the mechanism at 25℃or at 400℃is the combination of adhesive and abrasive wear,and at 200℃the mechanism is dominant adhesive wear.When the fretting of TiAlZr titanium alloy is running in the slip regime,the mechanism at 25℃is the combination of abrasive wear and delamination,the mechanism at 200℃is dominant oxidize wear with delamination and abrasive wear existing at the same time,and the mechanism at 400℃is dominant delamination.During room temperature to 400℃,the friction coefficient of TiN/TiN+Si/TiN multi-layer coatings is lower than that of substrate at fretting initial stage and steady stage,Besides the wear volume is obviously lower than which of substrate;The wear volume of TiN/TiN+Si/TiN multi-layer coatings increases with the increase of temperature.(3)From room temperature to 400℃,the friction coefficient of TiN/TiN+Si/TiN multi-layer coatings is lower than that of TiN/Ti composite coatings at steady stage;The wear volume of TiN/TiN+Si/TiN multi-layer coatings is lower than TiN/Ti composite coatings and the surface damage is smaller than TiN/Ti composite coatings.With the temperature changes from 25℃to 200℃,the wear mechanism of composite coatings firstly is delamination,and then is abrasive wear.When temperature increases to 400℃,the wear mechanism is again to be delamination.At the aspect of resisting elevated temperature fretting wear,TiN/TiN+Si/TiN multi-layer coatings is better than TiN/Ti composite coatings.
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