Densification characteristics, microstructure and wear behaviour of spark plasma sintering processed titanium-niobium pentoxide (Ti-Nb2O5) based composites

Abstract

The present study investigated the densification behavior, microstructure and wear properties of Ti-Nb2O5 based composites processed by spark plasma sintering (SPS). The SPS process was performed using sintering temperature of 1000 °C, holding time 10 min, heating rate 100 °C/min and applied pressure 50 MPa, as sintering process parameters. Optical and Scanning electron microscopy, X-Ray diffractometry, Relative density and hardness measurement, coefficient of friction and wear rate evaluation were used to characterize the composites produced. The CpTi and Ti-Nb2O5 composites attained full densification (relative densities ranged from 99.57 to 99.94%), and the total sintering times and densification stages were independent of the Nb2O5 reinforcement. However,the sinterability of the composites improved with increase in Nb2O5 content. The punch displacement curve of the Nb2O5 reinforced CpTi composite grades were higher compared to the CpTi. Also, the hardness values increased progressively with increase in Nb2O5 content. The microstructures that the addition of Nb2O5 resulted in structural transformation from lamellar (α) in the Cp Ti to bimodal (α + β) structures in the Ti-Nb2O5 composites accompanied with decrease in average grain size with increase in Nb2O5 content. The steady-state friction coefficients for all the composite samples ranged from 0.3 to 0.6. However, there was largely progressive increase in friction coefficient with Nb2O5 content. Generally, the wear resistance increased with increase in Nb2O5 content with the wear mechanism of the composites from wear track assessment, established to be mixed mode of adhesive and abrasive wear.