Correlation of microstructure and bio-tribocorrosion behavior of equal channel angular pressed pure titanium

Abstract

The effect of equal channel angular pressing (ECAP) strain (i.e., 1st to 4th pass) on the grain size and eventual mechanical and bio-tribocorrosion properties of commercially pure titanium (cp-Ti) has been investigated. Ultra-fine grains (UFG) of 0.8 µm size (from 12 µm) and yield strength enhancement to 785 MPa (from 381 MPa) have been observed for the ECAP 4th pass sample as compared to the annealed condition of cp-Ti. In addition, the maximum hardness increased by 101 HV to 293 HV in the 4th pass samples due to grain refinement caused by the ECAP process. Further, the tribocorrosion behaviour as a function of cp-Ti sample conditions in the simulated body fluid (SBF) has been evaluated. The ultra-fine-grained 4th pass sample shows a lower coefficient of friction (CoF) of ∼0.35 (from ∼0.5) and wear loss due to its enhanced strength than the annealed sample. Moreover, the ECAP 4th pass sample, because of its UFG, exhibits a more negative potential shift (∼0.82 V) as compared to annealed sample (∼0.88 V). However, this shift is marginal due to its low wear scar width and depth, which eventually induced less galvanic coupling effect in it. Abrasion and adhesion are the primary wear mechanisms for all the sample conditions.