Tribocorrosion of TiC-based composites incorporating Ni and Co binders in saline solutions

Abstract

Metallic binders impart necessary toughness to ceramic-metal composites, yet are vulnerable to corrosion and wear. Thus far, the tribocorrosion mechanism remains little understood, obstructing the design of durable composites for ocean drilling applications. Against this backdrop, we selected the TiC-based composites encompassing the Ni and Co binders having different standard electrode potentials as model systems, and studied their tribocorrosion behaviors with the aid of microscopic characterizations and first-principles calculations. Results showed that the TiC-Ni system maintained lower corrosion current densities at the pure corrosion condition, due to the reduced tendency of galvanic corrosion. Such system also realized lower coefficient of friction (COF) and wear losses at the pure wear condition, benefiting from the reduced adhesion at the sliding interfaces as well as the improved composite fracture toughness. Under corrosion-wear interactions, however, the TiC-Co system revealed alleviated material losses, as the rapid build-up of oxide tribolayers enhanced the surface hardness and facilitated the transfer layer formation. Thus, contrary to the intuition that corrosion-resistant binders should be beneficial to the tribocorrosion resistance, the current work highlighted the binder's ability to generate surface layers that helped to resist corrosion-accelerated wear, a point that needs to be emphasized in future development of robust composite materials.