SURFACE ALLOYING OF TUNGSTEN CARBIDE WITH TITANIUM, USING ELECTRON BEAM IRRADIATION

Abstract

The demand for higher performance products (car parts and elements parts) and special working conditions are the main reason to substitute components in cast iron and steel, with components made of "light alloy", such as aluminum and titanium alloys. These alloys are characterized by reduced hardness and wear behavior especially in abrasive wear, representing a severe barrier to their use in tribological applications.
Surface alloying process of titanium materials with tungsten carbide powder was made possible in a limited domain of energy process, from 300 W/mm to 330 W/mm. Microscopic structure of alloyed area consists of titanium carbide (TiC) distributed in phases of chromium-titanium (CrTi₄), titanium-tungsten (TiW) and cobalt-titanium (CoTi₂). Alloyed surface hardness with subsequent redoubles has values up to 748 HV_0.3 and superior wear resistance, assigned to wear hard phase of titanium carbide (TiC). It was also observed that the formation of cobalt-titanium phase (CoTi₂) led to a decrease in the coefficient of friction up to 0.365. Alloying process has led to an increase in the corrosion rate for TiWC. Areas of titanium alloyed with tungsten carbide powder (TiWC) possess residual compressive stresses, which may lead to an increased fatigue resistance of the material. The surfaces of titanium alloyed with tungsten carbide powder in the arreas of cobalt-chromium, present the best wear behavior in pin-on-disk tests, proving to be a better solution in applications where wear resistance is needed.