Tribological behavior of nanosecond-laser surface textured Ti6Al4V

Abstract

Titanium alloys are used due to their high specific strength and remarkable corrosion resistance. Their wear resistance however is poor, which in this paper is counteracted by laser surface texturing. Linear textures were created by the use of a nanosecond-pulsed laser, accompanied by melt bulges of resolidified material on the sides. Packing density, finishing procedure and atmosphere during laser texturing were varied between the experiments. Melt bulges lasered in air turned out to be tribologically beneficial in grease-lubricated sliding contact, reducing wear volume on Ti6Al4V significantly by up to a factor of 160, if a packing density of 5% or more was chosen. Further investigations of melt bulges with energy dispersive X-ray spectroscopy (EDX) and scanning transmission electron microscopy (STEM) revealed an increased content in interstitial oxygen and nitrogen and a purely martensitic α'-phase microstructure. Critical limitation of plastic deformation and a saturation of electronic bonds of the titanium atoms by interstitial elements is thought to be responsible for the reduction in adhesive tendency and therefore the pronounced decrease in wear.

The Effect of Position of Materials on a Build Platform on the Hardness, Roughness, and Corrosion Resistance of Ti6Al4V Produced by DMLS Technology

“…The resulting roughness of parts produced in an additive way is always the result of a combination of input parameters-in particular, the particle size of the powder used, melting conditions (laser power and speed, laser scanning strategy, layer height), or orientation of the produced part relative to the building platform [6,32,33]. The roughness affects implant-bone interaction, the friction coefficient, osseointegration process [3,34] (especially in porous structures [4][5][6][7]), and the fatigue life of the product [11]. Liu [1] notes that the roughness is affected by several factors: (1) the staircase effect related to the subsequently deposited layers; (2) the attachment of the partly melted particles to the surface, and (3) the presence of pores and other imperfections close to surface.…”

Influence of Interstitial Oxygen on the Tribology of Ti6Al4V

“…The work of adhesion also plays a role in the "stickiness" of the two contacting bodies. Speculatively, the chemical bonding characteristics and therefore the intrinsic work of adhesion between the two bodies could be affected by the presence of oxygen just like interface energies [23,24,40]. However, such electronic effects are usually small and certainly not abrupt.…”

“…Several methods of introducing interstitial atoms were successful in reducing wear on titanium alloys, such as ion implantation [17][18][19] or thermochemical treatments like nitriding and carburizing [20][21][22]. Also laser-induced chemical changes in Ti6Al4V can lead to significant improvements in its tribological behavior [23,24]. It appears that adhesive wear can be avoided and wear volume reduced by more than two orders of magnitude.…”

Wear Resistance Enhancement of Al6061 Alloy Surface Layer by Laser Dispersed Carbide Powders

“…Extremely high energy density at the surface of the processed object offered by lasers allows for the treatment of any material, even ceramics. Innovative surface treatments such as laser texturing can be applied to ceramic coatings (Al 2 O 3 –13%TiO 2 ) [ 2 ] on steel substrate, and also Ti6Al4V alloy [ 3 , 4 ]. Results indicate markedly improved tribological performance characterized by changes in the roughness and structure.…”