Preparation And Properties Of Gradient Bi-Continuous TiC/Fe Composites By Template Stacking

In this paper,gradient Ti C porous ceramics were prepared based on the demand of high-performance wear-resistant materials in the field of brake,and then bi-continuous Ti C/Fe composites were prepared with gradient Ti C porous ceramics as reinforcement phase,and their structures and properties were studied.Gradient Ti C porous ceramic reinforcement was successfully prepared by the template laminated impregnation pressureless sintering process.In the experiment,polyurethane sponge was used as template,Ti C as major raw material powder and a small amount of Ti powder and Mo powder were added as sintering aids.The gradient tic porous ceramics with continuous interface transition were prepared by the method of precursor impregnation and pressureless sintering.The effects of the pore size of sponge template and the coating times of slurry on the gradient structure were studied.The results showed that the Ti C porous ceramic gradient structure could be controlled by template aperture and coating times.The strength of porous ceramic preforms had an important relationship with the amount of slurry.The strength of porous ceramic preforms could be greatly improved by increasing the number of slurry hanging and changing the slurry hanging process.The porosity and compressive strength of the Ti C porous ceramics prepared by 5 times of slurry suspension were 82.95%and 3.52 MPa respectively.The gradient bi-continuous Ti C/Fe composite was prepared by pressureless infiltration with gradient Ti C porous ceramics as the continuous reinforcing phase.The influence of matrix composition and processing parameters on the infiltration effect was studied.The results showed that 45#steel had a good wettability with Ti C.After infiltration,it completely entered into the pores of Ti C porous ceramics.The ceramic skeleton maintained a three-dimensional network structure and formed a bi-continuous structure with the metal matrix.The micro analysis showed that the composite layers on both sides of the gradient interface of the composite had obvious differences,and the skeleton was in continuous transition at the gradient interface.The gradient bi-continuous composite had good mechanical properties.The25-40PPI?pores per inch?gradient composite prepared by 5 times of immersion had14.4%Ti C ceramic content.Its tensile,compressive and bending properties were obviously better than those of homogeneous composite.Ti C ceramic framework and iron matrix played a cooperative role in hardness strengthening.The average Vickers hardness of 25PPI composite layer was 3.51 GPa,and that of 40PPI composite layer was 4.09 GPa.The bi-continuous composite showed high wear resistance.With the increase of impregnation times of sponge template,the content of Ti C ceramic in the gradient composite increaseed,which made the wear resistance of the composite improve;while the friction coefficient of the composite decreased with the increase of the content of ceramic reinforcement phase,but it was both higher than 0.5,which showed a high level,so it was suitable for braking materials.In the experimental range,the wear rate and wear depth of the composite prepared by 5 times of immersion template were the lowest,which were 0.15×10^-9 mm³/N·m and 2.96?m,respectively.The friction coefficient was0.52,and the friction and wear performance was the best.Composite layers with different ceramic contents had different hardness and friction wear properties,which could meet the requirements of different wear conditions.