DEPOSITION OF CVD DIAMOND ONTO BORON-CARBIDE SUBSTRATES

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.