THE DEVELOPMENT AND CHARACTERIZATION OF TITANIUM BASED COMPOSITES REINFORCED WITH NIOBIUM-PENTOXIDE FOR MARINE AND PETROCHEMICAL APPLICATIONS

Abstract

The present study reports on the wear behaviour of spark plasma sintered commercial pure titanium (CpTi) and Titanium-Niobium pentoxide (Ti-Nb2O5) composites of varying weight percent (5, 10, and 15 wt.%) of Nb2O5 content in dry, acidic and saline environments for potential usage in marine and petrochemical applications. Scanning Electron Microscopy (SEM), X-Ray diffractometry (XRD), Relative density and hardness measurement, coefficient of friction, wear volume and wear rate evaluation (in dry, 3.5wt. % NaCl and 0.3M H2SO4 solutions), were used to characterize the Ti based material systems produced. The results revealed that the Nb2O5 addition resulted in the CpTi phase transforming from predominantly α-Ti phase to (α +β) Ti phases. The fully densified CpTi and Ti-Nb2O5 exhibited progressive increase in hardness of 143, 159, and 192% with increase in the Nb2O5 particles by 5, 10, and 15 wt. %, respectively. This increase was associated with particle, phase (transformation from α-Ti to β-Ti) and matrix strengthening (grain refinement) induced by the Nb2O5 particles. Also, the coefficient of friction which ranged between (0.3-0.49), wear volume (0.002-0.0062), and wear rates (0.001-0.006) were generally lower in the wet environments than the dry environment. However, the decrease in the wear volumes and wear rates with increase in the Nb2O5 wt. % irrespective of the environment, was linked to the presence of the harder Nb2O5 particles. Furthermore, the wear rates were observed to be more severe in the dry environment than the acidic and saline environments, largely due to the lubricating action of the fluids and reduction in adhesive plastic sheared tribolayer on the composite surfaces. The wear mechanisms were established to be adhesion and abrasion for the composites in the dry environment while predominantly abrasion and chemical attack induced wearing were mechanisms acknowledged to be operational for the wet environments.