The microstructural evolution occurring during sintering at 1600 degrees C
in two different phase mixtures of Ti(C,N) and Mo was studied. The mixture
of Ti(C,N)-Mo (1) was prepared using as-received commercial powders of Ti(C
,N) (particle size, 1.5-10 mu m) and Mo2C (1.5-2.5 mu m), and Ti(C,N)-Mo (I
I) using wet ball-milled powders of Ti(C,N) (0.2-1.5 mu m) and Mo2C (0.2-1.
5 mu m), followed by a decomposition treatment of Mo2C to Mo. It was shown
that, in both mixtures studied, most Mo atoms remained as an independent ph
ase component even after 40 h at 1600 degrees C. During the sintering treat
ment, particles of Mo were transformed into a coating of Mo around the Ti(C
,N) particles via surface/boundary diffusion. No (Ti,Mo)(C,N) rim structure
could be detected. The present results showed that there is hardly any int
er-diffusion and reaction between Mo and Ti(C,N) at high temperatures. The
diffusion mechanism therefore cannot be responsible for the formation of mi
xed carbide or carbonitride rims during the sintering of Ti(C,N)-based cerm
ets. (C) 1999 Elsevier Science S.A. All rights reserved.