Research Of The Dry Sliding Friction And Wear Properties Of In Situ (TiC+TiB)/Ti6Al4V Composites

(TiC+TiB)/TC4 composites with different TiC and TiB contents were prepared by in situ synthesis and enhanced phase particles were TiC and TiB.The influence of reinforced phase content,load and sliding speed on dry sliding friction and wear performance was studied by HT-1000 friction and wear testing machine.The volume fraction of the enhanced phase were 0,2.5%and 5%respectively,and the applied loads were 5N,10N,15N and 20N respectively.The sliding velocities were0.419m/s,0.628m/s and 0.837 m/s respectively.The microstructure and wear behavior of the materials were analyzed by means of optical microscopy,scanning electron microscope and Rockwell hardness tester.The hardness of the TC4 matrix alloy was 31.5HRC,and the hardness of the TMC2composite material was 34.2HRC,an increase of 8.6%,with little change in hardness.With a sliding speed of 0.419m/s and an applied load of 5N,the wear rate of TC4 was2.11×10^-6mm³/mm.The wear rate of TMC2 reached 1.03×10^-6mm³/mm,a decrease of51.2%,and the wear rate changed significantly.Composites exhibit excellent wear resistance.The TC4 matrix alloy was mainly ploughed wear and peel wear,and the composites were mainly abrasive wear and peeling wear,accompanied by oxidation wear.The debris of the TC4 matrix alloy was lumpy and chip.With the increase of the content of the reinforced phase,the size of the debris decreased and the particle size was smaller.Compared with TC4,the thickness of the friction layer of TMC1 and TMC2 decreased obviously,and the subsurface basically did not exist the deformation region.When the sliding speed was 0.419m/s and the applied load was 5N,the wear surface hardness of TC4,TMC1,and TMC2 composites was significantly higher than that of the substrate,which was 915.8HV,1076.8HV and 1103.2HV,respectively.The sub-surface hardness was slightly higher than the hardness of the substrate,from the grinding surface to the heart,the hardness decreased continuously and tended to a stable level,and the hardness of the composite material was greater than the hardness of the TC4 alloy.As the load increased,the wear rate of the base alloy and composite increased,and the average friction coefficient decreased.When the load changed,the friction coefficients of TC4,TMC1,and TMC2 composite materials fluctuated in the ranges of 0.48-0.55,0.42-0.52,and 0.39-0.47,respectively.The fluctuation range was small and the friction coefficient was relatively stable.The wear of the material was mild under low load.Fatigue wear and abrasive wear were the main wear as the load increased.As the load increased,the size of the debris increased and the wear increased.At low load,the friction layer of the material was thinner and loose,the thickness of the friction layer and the deformable layer increased at high load,and the friction layer became compact and uniform.The surface hardness of the material section increased with the increase of load.The wear rate and friction coefficient of the matrix alloy and composite decreased with the increased of the sliding velocity.Under the sliding speed of 0.419 m/s-0.628m/s,the wear rate decreased a lot,and the wear rate decreased less at 0.628m/s-0.837 m/s sliding speed.With the increase of the sliding speed,the groove depth of the TC4 grinding surface decreased,the scratch of the composite surface became lighter,and the exfoliation area became smaller and the wear degree decreased.As the sliding velocity increased,the wear debris increased obviously,and the friction layer of the cross section became homogeneous and compact,and the number of cracks in the friction layer decreased.With the increase of the sliding speed,the friction layer contained a large number of oxides,and its hardness was very high.It can protect the wear surface and reduce the wear rate.