| ZrO2?Y2O3?-Al2O3 composite ceramics have excellent mechanical properties and stable chemical properties,but poor tribological properties of ZrO2?Y2O3?-Al2O3composite ceramics greatly limits its application in the field of friction.In order to improve the tribological properties of ZrO2?Y2O3?-Al2O3-graphite composite ceramics,the uniformly dispersed fine graphite flakes were introduced into ZrO2?Y2O3?-Al2O3composite ceramics by a mechanical milling method.At the same time,ZrO2?Y2O3?based self-lubricating composite ceramics with better properties are expected to be prepared by this method.In this experiment,the ZrO2?Y2O3?-Al2O3-graphite composite powders were prepared by a mechanical milling method and a direct powder doping milling method,the composites were prepared by microwave sintering.The relative density,Vickers hardness,fracture toughness,flexural strength,friction coefficient and wear rate of the sintered body were measured;the evolution of phase and structure was analyzed,the friction and wear behavior and wear mechanism of ZrO2?Y2O3?matrix self-lubricating composite ceramics were discussed.The results show that 1)the annealing treatment before microwave sintering?1500?C,holding for 30 min?is conducive to avoid the formation of cracks and bubbles.The annealing process is sintering at 420?C and holding for 4 h;2)ZrC phase was generated in the ZrO2?Y2O3?-Al2O3-graphite composites after microwave sintering at 1500?C for 30 min,high hardness ZrC ceramic is conducive to improve the wear resistance of the composites;3)Without any dispersant or surfactant,the tribological properties of ZrO2?Y2O3?-Al2O3-4wt.%graphite composites prepared by the mechanical milling method are better than those of ZrO2?Y2O3?-Al2O3-4wt.%graphite composites prepared by the direct powder doping milling method.The friction coefficients and specific wear rate of ZrO2?Y2O3?-Al2O3-4wt.%graphite composites are 0.147 and 6.2 x 10-66 mm3/?N m?respectively;4)Reasonable ball milling time can improves the relative density and mechanical properties of ZrO2?Y2O3?-based self-lubricating composite ceramics prepared by the mechanical milling method.When the ball milling time is 24h,the comprehensive performance of the composite is relatively better;5)From the perspective of wear resistance,when thegraphitecontentisx=3.2wt.%,thecomprehensivepropertiesof ZrO2?Y2O3?-Al2O3-3.2wt.%graphite composites are superior,its relative density,Vickers hardness,fracture toughness,the flexural strength,friction coefficient and wear rate were 93.14%,967 HV,6.39 MPa·m1/2,413.21 MPa,0.159 and 3.4×10-6mm3/N m,respectively.the wear rate of the composite ceramic was reduced by approximately 48.14%compared with the wear rate of the 92.5Z7.5A composite ceramic;6)The wear mechanism of the ZrO2?Y2O3?-Al2O3 composite ceramics was dominated by plough groove and brittle fracture.The wear mechanism of ZrO2?Y2O3?-Al2O3-4wt.%graphite composite ceramics with ball milling time of 0h and 48h was dominated by abrasive wear.The wear mechanism of ZrO2?Y2O3?-Al2O3-4wt.%graphite composite ceramics with ball milling time of 2h was dominated by microcracks and abrasive wear.When the graphite content x=0.8,1.6,2.4 and3.2wt.%,the wear surface of ZrO2?Y2O3?-Al2O3-xwt.%graphite composite ceramics had wear debris and different degrees of delamination.When the content of graphite is 4 wt.%,the wear surface of ZrO2?Y2O3?-Al2O3-4wt.%graphite composite ceramics has continuous and compact graphite transfer film,which achieves self-lubrication effect. |
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