Preparation Of Porous Ceramic/Fe Matrix Composites By Lost Foam Casting

As the "Made in China 2025" being puting forward,the development of China mechincal and manufacturing industry has increased rapidly,and the demand for new-type and high-performance composite materials is increasing day by day.Ceramic/metal matrix composites have become an outstanding one among the numerous emerging materials because of their excellent wear resistance,high temperature resistance,and corrosion resistance.In this thesis,the Ni-P layer on ceramic by electroless plating technology was first proposed to improve the wettability between ceramic and iron.Porous ceramic/Fe matrix composites were also firstly produced by lost foam casting technology.Large-scale production and application can be realized by this production because of the simple process,short production and low cost.Microstructure,interface formation mechanism and wear morphology of composite were investigated by using scanning electron microscopy(SEM),X-ray diffractometer(XRD),energy dispersive spectroscopy(EDS)and Vickers hardness tester.The results showed that the plating speed of plating solution is stable and the plating effect is uniform after the electroless plating solution was optimized.At high temperature of 1420°C,the crystallization reaction of the Ni-P layer forms a cell structure,which is more conducive to the interface bonding.At high temperatures,the Ni-P layer on the ceramic surface dissolves in the Fe solution,therefore a high nickel solid solution formed.Due to the influence of temperature and element content at the interface,interfacial three-zone was created.Metel permeation zone(MPZ)which close to ceramic phase;excessive ? zone:flake graphite aggregation zone(FAZ);excessive ? zone:graphite nodules aggregation zone(NAZ).Composite with average apertures of 1-2mm,3-4mm,and 4-5mm accounted for 20.4%,17.2%,and 16.1%of the total volume of the castings,respectively.The average densities were 6.40 g/cm3,6.54 g/cm3,and 6.57 g/cm3,respectively.The average hardnesses were 361.2 HV,348.6 HV,and 345.7 HV,respectively.Among the three apertures of composites,the larger of ceramic volume,the lower density and the greater hardness they are.Under the same load,the coefficient of friction and abrasion loss of the composites are all less than ductile iron matrix.The abrasion curve of composite on the wear surface is smoother than ductile iron matrix,and the roughness is lower.The friction coefficient of composites remain stable with the increased wear load.In the friction and wear process,the main wear mechanisms of porous ceramic/Fe matrix composites are oxidative wear,adhesive wear and abrasive wear.Ceramics as the reinforcing phase in the composite formed hard bumps on the wear surface to support the load,which could prevent metal from plastic deformation.