Mi. De Barros et al., Influence of internal diffusion barriers on carbon diffusion in pure titanium and Ti-6Al-4V during diamond deposition, DIAM RELAT, 8(6), 1999, pp. 1022-1032
Diamond coatings were deposited on pure titanium and Ti-6Al-4V, at a temper
ature in the range of 600-750 degrees C, in a microwave plasma from CH4/H-2
and CO/H-2 mixtures. The influence on carbon diffusion of different interm
ediate layers, especially tungsten, niobium, titanium nitride and pure tita
nium previously deposited on titanium alloys by physical vapor deposition (
PVD) is reported. These intermediate layers are always composed of at least
two sub-layers: (1) an internal diffusion barrier and (2) an external tita
nium layer that allows some carbon diffusion to be maintained. After diamon
d deposition, X-ray diffraction (XRD) analysis and scanning electron micros
copy (SEM) observations coupled with energy-dispersive X-ray (EDX) analysis
of the final multilayer systems allow us to determine the diffracting phas
es, their lattice parameters and the efficiency of the different barriers.
The carbon diffusion coefficients in the titanium carbide phase and in the
alpha-titanium solid solution are deduced from an experimental study carrie
d out on pure titanium with or without an underlying diffusion barrier. The
results are compared to the carbon diffusion in Ti-6Al-4V alloy. This work
permitted us to calculate the carbon concentration profiles in both pure t
itanium and Ti-6Al-4V substrates. (C) 1999 Elsevier Science S.A. All rights
reserved.