The Two-Phase Region of TiC-Ni Alloy in Relation to the characteristics of Starting Titanium Carbide Powders

Abstract

The range of two-phase region and the binder or carbide phase composition in the phase region in TiC-Ni alloy were examined in relation to the characteristics of starting titanium carbide powders. The starting powders were prepared from TiO2 and TiH2. Produced titanium carbides have various carbon contents from 17.20 to 19.55%. Five sorts of TiC-30%Ni alloy systems, each different, according to the starting powders used, were vacuum-sintered at 1400°C for 1.5 hr. In each alloy system, the carbon content was strictly controlled and the various alloys with various carbon contents were sintered.The results obtained were as follows; it was concluded that the range of two-phase region or the compositions of both phases in the alloy systems were not affected by the characteristics of starting powders so far as the alloy systems could successfully be sintered. For example, the two-phase region was found in such cases to exist in the range of about 18.1-19.3% in carbide (converted values of carbon content of alloy to carbide). The maximum carbon content of this 19.3% (actual carbon content in carbide phase, 19.2%) appeared to be controlled by the dissolution of nickel in carbide. It has been suggested that the reasonable combined.carbon of starting titanium carbide powder needed for TiC base cermets should be in the range of at most about 18.5-19.2%, when the oxygen content in starting powders is less than about 0.1%.