Study On Preparation And Wear Resistance Of ZTA/High Chromium Cast Iron Macro-composite

In view of the difficulty of uniform distribution of ceramic particles in the metal matrix and the weak interface bonding between ceramic and metal in the preparation of ceramic/metal composite.A method named rapid-flow mixing followed by high-pressure compositing（FM-PC）was proposed,which required neither the preparation of preforms nor the modification of particles by coating them.Firstly,the Zr O₂ toughened Al₂O₃particles（ZTAp）reinforced high chromium cast iron（HCCI）composite（ZTAp/HCCI）was prepared by the FM-PC process,the thermodynamic conditions for the achievement of tightly mechanical bonding interface under pressure were discussed,and the formation mechanism of such interface was revealed.Then the microstructure,mechanical properties and thermal expansion property of the ZTAp/HCCI composite were studied.Meanwhile,the evolution of the mechanical bonding interface between ZTA and HCCI in the heating-holding-cooling process were also discussed.After that,the ZTA block reinforced HCCI composite（ZTAb/HCCI）was prepared using liquid forging process,the influence of preparation pressure and ceramic surface morphology on the interface bonding behavior was studied,and the interface bonding strength model between the bonding strength and process parameters was established.Finally,the wear behavior of the composite under dry sliding and impact abrasive wear conditions was studied.And the quantitative correlation between the impact abrasive wear loss of the composite and wear parameters was determined and the wear prediction model was established.The main results obtained are as follows:The conditions for the achievement of closed mechanical meshing interface for the ceramic/metal system with poor wettability under pressure were studied,including the required minimum work and the minimum applied pressure.The formation mechanism of the tightly mechanical meshing interface was revealed,including four stages of the contact of the ceramic and metal,the preliminary bonding,strengthening bonding and complete bonding.The ZTAp/HCCI composite material was prepared through FM-PC technique.The integrity of the composite without obvious defects was demonstrated,and the ZTA particles with a volume fraction of 54 vol%were distributed homogeneously in the HCCI matrix.A tightly bonded interface was obtained between the ZTA and HCCI,which was formed by mechanical bonding.The fracture surface morphology of the composite showed that the fracture occurred inside the particle rather than the interface debonding,indicating a relatively strong bonding between the matrix and particles.The ZTAb/HCCI composite sample was prepared under high pressure,the influence of preparation pressure and ceramic surface morphology on the bonding strength was studied.For the rough ceramic（Sa=2.046μm）,the shear strength rised from 16.73 MPa to 24.91 MPa（an increasing of 48.9%）when the preparation pressure varied from 40 MPa to 100 MPa,indicating that the increase of pressure can significantly increase the bonding strength.Under the preparation pressure of 100 MPa,the interfacial shear strength rised from 20.87 MPa to 24.91 MPa（an increase of19.4%）when the ceramic surface roughness varied from Sa=0.616μm to Sa=2.046μm,indicating that the increase of ceramic roughness can increase the strength.The response surface methodology was used to establish the quantitative correlation between the bonding strength of mechanical interface for the ZTAb/HCCI sample and the preparation pressure,ceramic morphology and ceramic temperature.The interface bonding strength model was obtained,and the influence of process parameters and their interactions on the bonding strength was analyzed.Under the dry sliding wear condition,the wear resistance of the ZTAp/HCCI composite was obviously higher than that of the unreinforced HCCI material,and the relative wear resistance of the composite to HCCI increased from 1.84 to 2.95 times when the applied load varied from 300 N to 900 N,which indicated the wear resistance of the composite was much better at higher load.Under the condition of impact abrasive wear,the wear volume loss of the ZTAp/HCCI composite increased with the increase of impact energy,and its relative wear resistance to HCCI varied from 2.35 to1.74 when the energy increased from 1.5 J to 4.5 J,which indicated that the wear resistance of the composite decreased with the increase of impact energy.Using response surface methodology,the quantitative correlation between the impact abrasive wear loss of the ZTAp/HCCI composite and the wear parameters（impact energy,impact frequency and wear time）was determined.The wear prediction model of the composite was established,and the influence of wear parameters on the wear performance was analyzed.