Boron carbide (B4C) is a hard, lightweight ceramic used in the nuclear
and aerospace industries. Depositing a CVD diamond coating onto its s
urface may increase its wear resistance and hence its value as a struc
tural material in advanced applications, such as gyroscope rotors. Hot
filament CVD has been used to deposit 2-4-mu m layers of polycrystall
ine diamond onto polished B4C blocks. Wie found that adhesion of the d
iamond coating was poor, with spontaneous delamination occurring. SEM
and scanning Auger microscopy determined that boron from the surface o
f the B4C was diffusing into the CVD diamond to a depth of about 0.1 m
u m. This left a B-depleted, C-rich layer al the diamond/B4C interface
which caused the delamination of the doped diamond film. (C) 1997 Els
evier Science S.A.