Improving the Wear Resistance of VT22 Titanium Alloy by Anodic Plasma Electrolytic Boriding

The effect of anodic boriding modes on the structure of the modified layer and the tribological characteristics of the treated titanium alloy has been studied. The structure, phase, and elemental compositions of the layer have been studied by X-ray diffraction analysis and electron microscopy with energy dispersive X-ray spectroscopy analysis. Surface roughness and microhardness distribution have been measured by the standard methods. The tribological characteristics of the borided alloy have been studied under dry friction conditions using a counterbody made of bearing steel. It has been found that the modified layer contains titanium dioxide (rutile) and a solid solution of boron in titanium with precipitates of the beta phase. A fivefold increase in the wear resistance of the alloy due to an increase in hardness and a decrease in the roughness has been achieved owing to boriding in a solution of boric acid and ammonium chloride at temperatures of 850–900°C for 5 min.