Dry Wear Characteristics Of TC21 Titanium Alloy At High Temperature

Titanium alloys have a wide range of applications in both military and civil applications due to their high strength,light weight,excellent corrosion resistance and high temperature resistance.At present,most of the research has focused on the friction oxides generated by the dry sliding wear line of titanium alloys,and relatively little research has been done on the alloy material itself.Therefore,this paper will focus on the microstructure and property changes of the wear surface and subsurface layers of TC21 alloy during dry sliding wear.In this paper,a pin-disk wear tester was used to perform dry sliding wear experiments on TC21 alloy with sliding speeds of 0.5 m/s and 1.0 m/s,temperatures ranging from 20 to 300℃,and loads ranging from 10 to 180 N.Under the condition of 1.0 m/s,the variation curves of volumetric wear rate versus experimental temperature were plotted for different applied loads.The variation curves of the volumetric wear rate versus the applied load were plotted at 0.5m/s for different experimental temperatures.The curves show the trend of the wear rate with experimental conditions and also show the mild-severe wear transition.Scanning electron microscope(SEM)、energy spectrum analyzer(EDS)、 confocal scanning laser microscope、Zeiss microscope and X-ray diffractometer(XRD)were used to observe and measure the wear surface and subsurface microscopic morphology,elemental content,microhardness and physical phase composition.It is observed that the TC21 alloy is divided into two stages during the wear process: mild wear and severe wear.When the sliding speed is 1.0m/s,the main wear mechanism in the minor wear stage contains adhesive wear and minor plastic deformation,and the main wear mechanism in the severe wear stage contains adhesive wear and severe plastic deformation.When the sliding speed is 0.5m/s,the main wear mechanisms in the minor wear stage include abrasive wear,oxidation wear,peeling wear and mild plastic deformation,and the main wear mechanisms in the severe wear stage include adhesive wear and severe plastic deformation.It was found that the mild-severe wear transition is accompanied by a process of strain hardening to softening of the subsurface layer,and that the surface softening in the severe wear condition is caused by dynamic recrystallization of the substrate.Using an approximately linear relationship between the applied load and the critical experimental temperature of the mild-severe wear transition,the critical dynamic recrystallization temperature at which the severe wear transition is reached can be calculated.It was also found that oxidation does not occur on the wear surface at a medium sliding speed of 1.0 m/s,and oxides are generated on the wear surface at a low sliding speed of 0.5 m/s.