Properties of Ti_xC_{1 - x} films coated on molybdenum by magnetron sputtering

Properties of Ti_xC_{1 - x} (0.3 ≤ x ≤ 0.6) films deposited onto molybdenum have been examined as functions of their chemical composition. Ti_xC_{1 - x} films about 4-6 μm thick were deposited onto a sintered molybdenum substrate at 600 °C by magnetron sputtering. The near-stoichiometric Ti_xC_{1 - x} (x ≈ 0.5) was found to be the most thermally stable. Titanium excess Ti_xC_{1 - x} (x > 0.5) loses titanium by evaporation and changes its surface morphology above 1200 °C. However, excess titanium will improve the ductility of deposited films. Strong compressive stress was observed in carbon excess Ti_xC_{1 - x} (x < 0.5). The carbon excess Ti_xC_{1 - x} is more resistant against thermal evaporation than the stoichiometric compound. However, enhanced diffusion of molybdenum atoms into the carbon excess Ti_xC_{1 - x} takes place, with the formation of Mo₂C. This Mo₂C formation nearly prohibits the use of carbon excess Ti_xC_{1 - x} films coated on molybdenum as the first-wall material in fusion devices.