Titanium Alloy Ti6Al4V’s Corrosion Resistance Behavior by Double Glow Discharge Plasma Hydrogen-Free Carburizing Process

The surface-modified Titanium alloy Ti6Al4V was obtained in the process of the double glow discharge plasma hydrogen-free carburizing. The high purity solid graphite as the source cathode supplied the carbon elements; pure titanium and its alloys were used as the cathode and argon as the working gas. At certain pressure and voltage, the glow discharge appeared between cathode and anode, source cathode and anode. The carbon plasma flux, including carbon atoms, ions, sputtered by argon ions diffused into the substrate, which depended on ions bombardment and thermal diffusion at a negative voltage. High purity solid graphite cathode was done in a honeycomb shape or grid shape. A layer with TiC and C phases was formed during the process. Surface hardness was increased by four times due to the presence of TiC and C phases, and wear resistance was enormously improved. The C concentration and hardness of alloying layer changed gradually with the depth. The corrosion properties of hydrogen-free carburized specimens were tested in the solution of 5% NaCl and 5% H2SO4, using electrochemical corrosion method. The results showed that the corrosion resistance of carburized specimens was significantly improved in 5% H2SO4 solution.