Study Of Corrosion Resistance Of Titanium By Glow Plasma Discharge Hydrongen-free Carbonizing

Titanium is widely used in the field of aerospace, bioengineering, oil industry, atomic energy and other industries due to its low weight, high strength ratio, and outstanding corrosion resistance in the atmosphere, water and oxidizing medium. However, titanium has poor corrosion resistance in thermal acidic solution, reducing acid and solution containing abundant chloride ions.The corrosion resistance of titanium in thermal acidic solution, reducing acid and solution containing abundant chloride ions can be improved by alloying. One of the methods to improve the corrosion resistance of titanium is matrix alloying by the noble metal such as palladium (Ti-0.2Pd). However, titanium-noble metal alloy is not widely used for its cost. TIMET developed a new titanium-carbon binary alloy to improve corrosion resistance. The mechanical properties of titanium-carbon binary alloy will decrease due to the high content of carbon. Another method to improve the corrosion resistance of titanium is surface alloying by the carbon.In this paper, titanium surface is alloyed by carbon element by using double-glow plasma technology. The target used was a pure graphite disc. Another cathode was titanium. Argon was used as the sputtering gas. The hollow cathode effect of the glow discharge is used to heat the titanium substrate. The microstructure, phases, composition, Vickers hardness and corrosion resistance of titanium with carburized layer were studied. The results show that:1、The thickness of carburized layers is significantly affected by the heating temperature and the holding time. The thickness of carburized layers increases with increasing the temperature and holding time. The relationship between the diffusion coefficient and the heating temperature accorded with the Arrhenius manner. The value of diffusion activation energies was13.6kJ/mole (0.14eV).2、The implanted carbon ion and sputtered carbon atoms reacted with titanium atom to format carburized layer. The carburized layer consists of two layers. The depth of outer layer is about20um. There is distinct interface between outer layer and interior layer of carburized layer, while there is no distinct interface between carburized layer and alloy matrix. The depth of carburized layer was not less than100μm at950℃for holding3h. The content of titanium carbide gradually decreased with increasing the depth of carburized layer. The micro-hardness of carburized layer was much higher than that of titanium matrix.3、The TA2with carburized layer exhibits more notable open circuit potential, higher charge transfer resistance and lower corrosion current density in3.5wt.%NaCl solutions, and80wt.%H2SO4. The carburized layer improves the corrosion resistance of TA2.