DIRECT CARBIDE SYNTHESIS BY MULTIPULSE EXCIMER-LASER TREATMENT OF TI SAMPLES IN AMBIENT CH4 GAS AT SUPERATMOSPHERIC PRESSURE

Successful carbidation of Ti in a layer forming on the surface of a Ti sample submitted to multipulse excimer (lambda=308 nm) laser treatmen t in CH4 at a slightly superatmospheric pressure is reported. The laye r is only surface contaminated with oxygen while its main part consist s of fcc TiC. The layer apparently ends with a tail of carbides with l ow C content, extending deeper into the sample's bulk. The characteris tics of the synthesized layer are suggested to be related to the pecul iarities of the chemical synthesis which are enhanced by gas propulsio n into a melted layer under the recoil action of a plasma evolving in front of the sample. A cavitation mechanism inside the melted surface layer in order to account for plasma initiation is proposed. This mech anism also facilitates the strong substance propulsion into the sample 's bulk.