Diamond particles and films were grown on graphite substrates using hot-filament CVD method with a pure hydrogen feed. After deposition, graphite substrates showed strong etching effects. A trough of 1 mm deep and 4-5 mm wide was formed in the graphite opposite to the filament. Scanning electron microscopy and micro-Raman spectrum demonstrate that diamond has grown both inside and near the edge of the trough. The results are discussed with respect to the possible precursors of diamond deposition and the effect of atomic hydrogen interaction with graphite substrates.