Enhancing Friction & Wear Properties by Heat Treating Titanium
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. 聽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). 聽Because of this, metal-to-metal applications encountering friction and wear considerations require a surface treatment for adequate serviceability. 聽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. 聽Like other diffusion processes, the depth of the diffusion zone is dependent on the time of the treatment. 聽For alloy Ti-6Al-4V with a core hardness of 30 HRC, 麻豆国产精品 has generated hardnesses as high as the mid-60鈥檚 to upper-60鈥檚 HRC (converted from HV 25gf) at a depth of 0.0076mm (0.0003鈥�), followed by a gradual decrease in hardness to the core over a distance of 0.25mm (0.01鈥�). 聽Shorter cycle times have produced hardnesses in the mid-50鈥檚 to high-50鈥檚 HRC and shallower total case depths.
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