Enhancing Titanium Friction & Wear Properties

For all of the known benefits of titanium alloys in all sorts of applications, from medical to aerospace to automotive, titanium is also known to exhibit poor tribological properties.  That is, it has a high coefficient of friction (COF) when in moving contact with essentially all structural metals, resulting in poor sliding and adhesive wear resistance that leads to failure by galling (cold welding).  Because of this, metal-to-metal applications encountering friction and wear considerations require a surface treatment for adequate serviceability.  One such treatment is solution nitriding, which is performed in a vacuum furnace using partial pressure nitrogen gas at elevated temperatures in the annealing range. Solution nitriding is classified as a diffusion process where nitrogen gas dissociates and nascent nitrogen is adsorbed and diffused into the titanium matrix.  Like other diffusion processes, the depth of the diffusion zone is dependent on the time of the treatment.  For alloy Ti-6Al-4V with a core hardness of 30 HRC, Solar Atmospheres has generated hardnesses as high as the mid-60’s to upper-60’s HRC (converted from HV 25gf) at a depth of 0.0076mm (0.0003”), followed by a gradual decrease in hardness to the core over a distance of 0.25mm (0.01”).  Shorter cycle times have produced hardnesses in the mid-50’s to high-50’s HRC and shallower total case depths.

Download Technical Paper