Abstract
It has been found out by the present authors that the amount of binder phase of TiC-Mo2C-Ni cermet containing nitrogen sintered in vacuum was often decreased in the region near the specimen surface. Then, the study was made to describe the reason why such a binder poor region (BPR) appeared in nitrogen added cermet. The TiC-10 vol%Mo2C-(0-40) vol%TiN-10 vol%Ni alloys with different carbon contents were in vacuum sintered at 1400°C for different times, and used as specimens.
The BPR with the thickness of about 500μm from the surface was generally observed, when the carbon and TiN contents in the cerinet were comparatively high and more than about 10 vol%, respectively. The BPR was also observed in the specimen, re-sintered after the surface region of firstly sintered specimen was ground off to remove BPR. The BPR formation was suggested to be caused by the fact that the region near the surface was carburized in contact with the sintering atmosphere, because denitrification during sintering process took place in the case of cermets with relatively high carbon; resulting in the surface region to be higher in the carbon content than the inside, which made Mo and Ti atoms diffuse out from inside to surface region.
