Fabrication And Performance Of Ni/TiC_x Composites By Pressureless Infiltration

TiCx has the advantages of high hardness,high melting point,good wettability with metals and wear resistance.Nickel has high melting point,strong oxidation resistance and thermal corrosion resistance,and can keep its performance unchanged in high temperature environment.Nickel and TiCx were selected to prepare composite materials with both advantages by pressureless infiltration method for cermet cutting tools.In this paper,TiCx preforms were fabricated firstly,then Ni was infiltrated into the preforms by pressureless infiltration process,and bi-continuous phase Ni/TiCx composites were prepared.The fabrication process of TiCx preform,pressureless infiltration process,reaction mechanism,microstructures and mechanical properties of cermet composites were investigated.The experimental results show:(1)Using Carbon powder and Titanium powder were mixed according to the proportion,and then mixed with a certain proportion of PVB alcohol solution.Preparation of raw material powder and successfully prepared TiCx porous ceramic preforms with controlled porosity by pressureless sintering method.The porosity of the preform prepared by pressureless sintering can be adjusted from 2.9%to 28.5%at 1500℃ and 120 minutes heat preservation.The ceramic skeleton of preform has sufficient strength and pore connectivity,which meets the requirement of pressureless infiltration for preform.(2)The reaction mechanism of Ni/TiCx composites is that molten metal nickel enters into the pore of TiCx preform under capillary action,and some metal nickel reacts with Titanium in TiCx with defect site structure to form Ni-Ti compound.Metallic phase and ceramics interlace in composites are interlaced and connected in three dimensions,showing a bi-continuous phase network structure.(3)The flexural properties of Ni/TiCx composites will be improved significantly with the increase of the porosity of TiCx preform.The bending properties of Ni/TiCx composites prepared by TiC0.5 preform with porosity of 18.8 ± 0.6%have the best flexural properties,with flexural strength of 715.9 MPa and fracture toughness of 19.50± 0.30 MPa.m1/2.However,the Vickers hardness of the composite decreases with the increase of the porosity of TiCx preform.The Vickers hardness decreases from 10.21 ± 0.12 GPa to 8.33±0.11 GPa when the load is 200 N.(4)The flexural properties of Ni/TiCx composites will also increase with the increase of carbon content in the preform.Among them,Ni/TiC0.6 composites have the best bending strength of 825.9 MPa and fracture toughness of 22.55± 0.90 MPa m1/2.The Vickers hardness of the composites increases slightly with the increase of carbon content.From Ni/TiC0.45 to Ni/TiC0.55,the Vickers hardness of the composites increases from 8.16± 0.20 GPa to 9.68±0.16 GPa when the load is 200 N.Most of the metal phases in Ni/TiCo 6 are pure nickel,and only a small amount of alloys.So the Vickers hardness of Ni/TiC0.6 is only 6.52±0.17 GPa and slightly lower than others.