Effect of Ti-Si-Fe alloy addition on structure and properties of Si3N4 bonded SiC refractories
In order to improve the densification of Si3N4 bonded SiC refractories and reduce the nitriding temperature of Si powder,Si3 N4-bonded SiC refractories were produced by reaction sintering at 1 350 ℃ for 5 h under an carbon embedded atmosphere,using SiC particles and fine powder,and Si power as the main raw materials,and introducing Ti-Si-Fe alloy extracted from high-titanium blast furnace slag to partial-ly replace the Si powder.The effects of the Ti-Si-Fe alloy addition(0,1.8％,3.6％,5.4％and 7.2％,by mass)on the nitriding behavior of Si powder,as well as the mechanical properties and microstructure of the material were investigated,and the nitriding reaction sintering mechanism was also explored.The re-sults show that:(1)with the increase of the Ti-Si-Fe alloy addition,the cold mechanical properties and the hot modulus of rupture of the refractories are obviously improved,and the refractoriness under load ex-ceeds 1 700 ℃;the property enhancement is slowed down with Ti-Si-Fe alloys addition above 3.6％;(2)Ti-Si-Fe alloy promotes the complete nitridation of Si powder and the reaction sintering of the material at a lower temperature;the volume growth during the nitridation process of the Ti-Si-Fe alloys and Si powder can effectively fill pores,nitriding products improve the bonding state between aggregates and matrix,and that inside matrix,thereby increasing the densification and improving the mechanical properties of the ma-terial;(3)after the introduction of Ti-Si-Fe alloys,the liquid phase rich in Ti,Si,N,and Fe components is formed in the reaction system;besides the traditional VS and VLS mechanisms,the dissolution-precipitati-on mechanism plays a leading role in the formation of short columnar β-Si3 N4 and granular TiN;the cross-linked α-Si3N4 whiskers,short columnar β-Si3N4 and granular TiN enhance the mechanical properties of the material.
Ti-Si-Fe alloyreaction sinteringSi3N4 bonded SiC refractoriesdensificationdissolution-pre-cipitation
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