Formation of nano-structured tribolayer on Ti-6Al-4V during sliding in a phosphate buffer saline solution

The formation of a tribological layer (i.e., tribolayer) affects friction and wear behavior during sliding. The mechanisms involved can be better understood by the characterization of this layer. The wear corrosion behavior of Ti 6Al 4V was studied using a reciprocating ball-on-flat tribometer at a frequency of 1 Hz and under normal loads of 1 N, 5 N, and 15 N against an alumina ball for 3600 cycles of sliding in a phosphate buffer saline (PBS) solution. Scanning Electron Microscopy (SEM) images, along with EDS analysis showed a greater coverage of a tribolayer under a normal load of 15 N. Transmission electron microscopy (TEM) studies indicated that a tribolayer with thickness up to 1000 nm, consisting of nanograins with diameters of less than 10 nm, formed on the deformed wear surface of Ti 6Al 4V under a normal load of 15 N. This protected tribolayer, under normal loads of 5 N and 15 N, resulted in a decrease of 40% in the coefficient of friction and a 15-20% reduction in the specific tribocorrosion rate compared with that at the lower applied load.