Preparation And Wear Properties Of Self Nanocrystallined Abrasion Resistant Layer On Rotary Cutter

Wear is common in industrial production,and huge economic and energy losses are caused each year due to wear.A large number of Scholars in materials at home and abroad are conducting research on wear resistance of metal materials.In the field of agricultural machinery,the parts in agricultural machinery which work in the soil are worn rapidly,which brings great loss to the mechanized production of agriculture.In this study,the surface self-nanocrystallization technology was applied to the agricultural machine parts which works in the soil,such as the rotary cutter.The purpose of this paper is to improve the wear resistance of the blades,and explore the corresponding performance change mechanism to obtain the friction and wear mechanism..In this paper,the rotary cultivator was used as the research object.The surface nanocrystallization technology was selected,and the ultrasonic impact technology was used as the technical means.Analysised by three aspects: friction and wear test,hardness test and microstructure inspection.With the vertical universal wear test bench,soil wear test bench,micro hardness tester,metallographic microscope,X-ray diffractometer and other equipments,The effects of different ultrasonic impact times and different annealing temperatures on the properties of the substrate were investigated,and the corresponding friction and wear mechanism was obtained.Through the research,the results obtained in this paper are as follows:1)When the time for ultrasonic impact does not exceed 5 min,the wear loss and friction coefficient decreased with the increase of the time for ultrasonic impact.With the further extension of impact time,the wear loss and friction coefficient both increased.However,in the environment of soil,the weight loss of the material increased with the increase of the impact time.2)After the ultrasonic shock treatment,the hardness of the surface of the material had been significantly improved.The longer the impact time continued,the greater increase generated in surface hardness.The biggest value is 301.02 HV0.1,which is equivalent to 1.79 times than that of the substrate.The hardness value from the surface layer to the core portion gradually became smaller.When it is about 150 ?m from the surface,it tends to coincide with the hardness of thesubstrate.3)After the ultrasonic shock treatment,the grains on the surface of the material showed a gradient change from small to large.When the ultrasonic impact time was 5 min,the thickness of the severely deformed layer and the transition layer reacheed the extreme value.When the impact time continued to increase,the thickness of the severely deformed layer and the transition layer didn't continue to increase,but the refinement phenomenon of grain in the surface layer was more obvious.4)The wear resistance of the samples annealed at 200 ° C and 300 ° C had improved than those which has not been annealed,but the wear resistance decreased after annealing at 400 ° C.5)After the annealing treatment,the nanocrystallines generated by ultrasonic impact appeard to grow.The microhardness value of the surface of the samples decreased with the increase of temperature,and the grain size increased with the increase of annealing temperature.According to the research results in this paper,the ultrasonic impact technology can improve the wear resistance and hardness of the rotary cutters.The longer the impact time continues,the smaller grain size on the surface is,and the greater increase generated in hardness and wear resistance.However,if the impact time is too long,the plasticity will be insufficient,and performance of the wear resistance will be degraded under the dry friction test environment.The annealing treatment can release the residual stress generated by the ultrasonic impact,but if the annealing temperature is too high,the growth of the grain size weakens the grain refining effect caused by the ultrasonic impact,resulting in a decrease in performance.Through the experimental investigation,it can be concluded that the optimum processing parameters are impacting 5 min,annealing at 300 ° C,and preserving 30 min.Under the environment of the universal wear test machine,the wear resistance increased by 3 times,the friction coefficient increased by 2.29 times,and the surface hardness improved by 1.68 times.The grain size on the surface was refined to 32.53 nm.