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Ti6Al4V alloy is the most widely used titanium alloy due to its attractive properties such as heat resistance, strength, plasticity, toughness, formability, weld-ability, corrosion resistance and biocompatibility. However, the main problem with titanium and its alloys is that they have poor tribological performance. Boriding seems to be the effective way to improve the tribological performance of titanium alloys. Titanium borides have an attractive combination of low density, high hardness, excellent wear, and corrosion resistance. In this study, Ti6Al4V alloy was borided in a solid media at 1100°C for 20 h. The microhardness profile was studied by a Vickers indenter. The hardness value of surface increases from 330 HV to 2789 HV. Wear experiments were performed in Ringer's solution that simulates human body environment. It was observed that boriding process improved tribological performance of Ti6Al4V alloy under all test conditions. © 2018 Polish Academy of Sciences Institute of Physics. All rights reserved.

In the present study, gears made of 21NiCrMo2 (AISI 8620) steel were subjected to heat treatments including carburizing, decarburizing, boriding and hardening. Carburizing, decarburizing and boriding were performed in a gaseous atmosphere, a salt bath consisting of 60% NaCl and 40% NaCO3, and a liquid medium containing borax and silicon carbide, respectively. Borocarburazing was carried out in two steps: carburizing and then boriding. Some specimens were treated to obtain different carbon concentrations and to observe the effect of carbon content on the boriding process. This process, consisting of carburizing followed by decarburizing and finally boriding, is named borodecarburizing. The microstructures and phase compositions of the diffusion layers were examined by means of X-ray diffractometry, scanning electron microscopy and optical microscopy. The microhardness profiles of these layers were studied by a Vickers indenter. The hardness value obtained by the borodecarburizing process is 10% higher than a borocarburized specimen’s hardness. One-phase iron boride zone (Fe2B) was observed in the layers. This phase is preferred due to its mechanical properties.

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