Oxygen-diffused titanium as a candidate brake rotor material

Titanium alloys are one of several candidate materials for the next generation of truck disk brake rotors. Despite their advantages of lightweight relative to cast iron and good strength and corrosion resistance, titanium alloys are unlikely to be satisfactory brake rotor materials unless their friction and wear behavior can be significantly improved. In this study, a surface engineering process - oxygen diffusion (OD) - was applied to titanium rotors and has shown very encouraging results. The oxygen-diffused Ti-6Al-4V (OD-Ti64) was tested on a sub-scale brake tester against a flat block of commercial brake lining material and benchmarked against several other Ti-based materials, including untreated Ti-6Al-4V (Ti64), Ti-based metal matrix composites (MMCs), and a thermal spray-coated Ti alloy. With respect to friction, the OD-Ti64 outperformed all other candidate materials under the imposed test conditions with the friction coefficient remaining within a desirable range of 0.35-0.50, even under the harshest conditions when the disk surface temperature reached nearly 600 °C. In addition, the OD-Ti64 showed significantly improved wear-resistance over the untreated Ti64 and was even better than the Ti-based composite materials.