Fabrication Of ZTA-TiC-Fe Composites By Combustion Synthesis Under High Gravity And Study Of Their Wear Mechanism

Advances in tool materials determine the development and application of high-end manufacturing technology.Ceramic cutting tools for high speed cutting is one of the most important tool materials,which is used to many fields.However,in the process of using ceramic tools,the blade may become fractured due to low toughness.This largely restricts the working efficiency of high-end CNC machine tools.Therefore,the study of toughening ceramic tool materials and extending their service life has important economic and social benefits.The ZTA-TiC-Fe?ZrO₂ toughened Al₂O₃,ZTA?composites with high toughness and high wear resistance were fabricated by high-gravity combustion synthesis,which combined the metal toughening and ZrO₂transformation toughening for toughening the widely used Al₂O₃-TiC ceramic tools.The relationship of process,structure and wear resistance was studied.The results for the process show that the ZTA-TiC-Fe composites produced by casting method under high gravity 800g¹600g.which used the raw materials of Al/Fe₂O₃/ZrO₂/Ti/C system.It is the best component that ZTA is 60 vol%,TiC and Fe is20 vol%respectively.The results of the microstructure show that tetragonal Zr O₂ is distributed in Al₂O₃ matrix with submicron fiber rods and fibrous laminates,and the ZTA eutectic ceramics formed in the three-dimensional network structure form the ceramic skeleton of composite materials.The metal Fe is distributed evenly in the three-dimensional ZTA ceramic skeleton.The TiC micron particles are distributed in the interface of ZTA ceramics and metal Fe,forming a dense shell structure with spherical Fe,which is a honeycomb interlaced with ZTA ceramics.This microstructure toughened Al₂O₃-TiC ceramic material for combining many toughening mechanism,such as crack deflection,crack bridging,crack nail pierced,fiber pull out and micro crack growth.The results of the performance show that hardness is 13GPa,bend strength is485±15MPa,compress strength is 1900MPa,fracture toughness is 11.2 MPa·m^1/2,which is three times to Al₂O₃-TiC duplex ceramic.The average thermal expansion coefficient of ZTA-TiC-Fe composite materials is 4.5×10^-6/?at room temperature to600?,which is closed to that of sapphire(5×10^-6/?).The conductivity of ZTA-TiC-Fe composite materials is 0.5 MS/m,which is equivalent to 5%of pure iron.These composites materials can be machined by spark wire cutting,which alleviate the difficulty of machining ceramic composite materials.ZTA-TiC-Fe composite materials have three times higher abrasion resistance than alloy steels under Al₂O₃ grinding media.When the grinding medium is the electroplated diamond disc,ZTA-TiC-Fe composite materials have ten times higher abrasion resistance than sintered alumina and is equivalent to the hard alloy YT15.The friction and wear mechanism of ZTA-TiC-Fe composites is micro-plough and micro-strip,respectively.This paper presents an new method named high-gravity combustion synthesis,which yields high temperature over 2000?without heating.The composites were fabricated and densificated quickly.A series of good performance composites will be developed for the detail research to the relationship of process,structure and performance.