Study On The Arcadded Glow Discharge Plasma Non-hydrogen Carburizing On Titanium Alloy Surfaces

Titanium alloys, such as Ti-6Al-4V, are used extensively in engineering application because they offer many advantages such as high strength and toughness, light weight, excellent corrosion resistance, and good producibility. Titanium alloys are restricted in application owing to its inherent shortcomings such as sensitive to adhesive wear, fretting wear.The improvement of material's tribological function is reflected by the main two aspects: first, reduce the material's friction coefficient; second, increase the wear resistance of material. Consider the graphite to have very excellent property of reducing friction. On the other hand, TiC exhibits high hardness and high tribological compatiblity. So if we had evolved a special penetrated layer which composed of the TiC and the dissociative C that we would provide titanium alloy surfaces with improved tribological properties in terms of low friction and high resistance to wear.A major concern when using titanium alloys as structural components is their compatiblity with hydrogen. Small amounts of hydrogen, usually a few hundred parts per million(ppm) by weight, have been found to significantly degrade the load carrying capability of titanium alloys.Internal hydrogen has been shown to casue sustained-load crack growth in titanium alloys. Sustained-load crack growth rates and threshold stress intensities depend on the hydrogen concentration. Similarly, hydrogen can increase fatigue crack growth rates in 7 titanium alloys, particularly in the low temperature regime. But now in common use air carburizing , vacuum carburizing and plasma carburizing etc. These crafts none not have relations with hydrogen element. There is always hydrogen element to seep into the subtrate. The direct performance is the material's plasticity and tenacity descend.The process and mechanisum of the arc-added glow discharge plasma non-hydrogen carburizing on titanium alloy (Ti-6Al-4V) surfaces are studied in this paper. High purity and high strength graphite was selected as cathode arc source. The carburizing layer thickness of 25~30 m was obstained at 980~1050℃, 20~30 min. The carburizing layer is composed of the TiC and dissociative C. The microhardness of titanium alloy surfaces attained 936 (HV), the coefficient of friction declined to 0.08. Moreover, passing the PS 168 electricity chemical corrosion experiment, we learned that the corrosion resistance of titanium alloy was also enhanced. The corrosion resistance of plamas non-hydrogen carburizing layer was 7 times of TC4 in 0.5mol/L H2SO4 and 3 times of TC4 in 1.0mol/L H2SO4.Using the XRD, SEM, AES, XPS, phases and structure of carburizing layer were determined.