Influence of nitrogen Gas pressure on the miscibility Gap in the Ti-Zr carbonitride system

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• 作者：Ida Borgh^a ; Susanne Norgren^b ; Annika Borgenstam^a ; John Å ; gren^a ; ^john@kth.se
• 关键词：Cemented carbides ; TiC ; ZrC ; Miscibility gap
• 刊名：International Journal of Refractory Metals and Hard Materials
• 出版年：2012
• 期刊代码：91_02634368
• 类别：et
• 出版时间：May, 2012
• 卷：32
• 期：Complete
• 页码：11-15
• 文件大小：807 K

摘要

The microstructure of cemented carbides with a gradient structure at the surface consists of WC, cubic carbonitrides and a binder phase. The carbonitrides can, for example, consist of Ti(C,N)-Zr(C,N) where it is reasonable to believe that there is a miscibility gap with Ti-rich and Zr-rich carbonitrides. In the present work, the effect of the N₂-gas pressure on the equilibrium composition of the miscibility gap in the (Ti,Zr)(C,N) system has been investigated. In the study, the carbonitride system is in equilibrium with: WC, liquid binder, graphite and, N₂-gas of different pressures. Both Fe and Co are used as binder phase to study the effect of the binder phase. The results verify that there is a miscibility gap in the carbonitride system and that the region of the miscibility gap will change when N is introduced. There is a critical N₂-gas pressure lower than 0.1 bar and above that pressure the compositions of the carbonitride are rather constant as a result of the formation of a surface rim.