IBAD MoS2 lubrication of titanium alloys

MoS2 coatings were deposited by ion-beam-assisted deposition (IBAD) with and without a 30 nm TiN interlayer on Ti, Ti-6Al-4V, and steel substrates and slid in dry air against Ti-6Al-4V and steel under two different contact conditions. Ln the constant load condition, the friction coefficients for coated Ti alloys sliding against Ti ranged from 0.02 to 0.06, while endurance ranged from 30 to 625 krev. The tribological behavior was independent of TiN interlayer and was similar to that for MoS2-coated steel sliding against steel. Shear strength parameters S-0 and alpha of IBAD MoS2 were measured on Ti-6Al-4V by varying the mean hertzian pressure, 0.28 GPa less than or equal to P-H less than or equal to 1.3 GPa; S-0 ranged from 12 to 19 MPa and alpha ranged from 0.005 to 0.021, similar to sputter-deposited MoS2 on steel. At P-H=1.3 GPa, the Ti alloy was loaded beyond its elastic limit, but the 300 nm thick IBAD MoS2 was able to protect the substrate by maintaining integrity and lubricity.