Anti-wear hierarchical TiC enhanced cermet coating obtained via electrical discharge coating using a reduced graphene oxide nanosheets mixed dielectric

Abstract

The use of a powder mixed dielectric is one of the promising measures to overcome defects such as non-uniform thickness, voids and micro-cracks of hard coatings obtained via the electrical discharge coating (EDC) process. The quest for finding appropriate powders suspended in EDC dielectric still continues. In this paper, reduced graphene oxide nanosheets (RGONS) are explored as the additives of EDC dielectric to fabricate TiC containing composite coatings with superior tribological performance. The influences of RGONS on the surface integrity, microstructure and tribological performance of the as-prepared coatings are investigated. RGONS with lipophilic modification effectively reduce spark energy and disperse the discharges throughout the machined surface due to their uniform dispersion in the discharge gap. This allows the formation of compact coatings with banded microstructure composing of a mixture of equiaxed and columnar TiC grains within the martensite matrix. Such unique microstructure improves the as-prepared coatings’ resistance to adhesion and abrasion wear, as well as fatigue and fracture. As a result, they show obviously lower coefficient of friction and wear rate compared to the coatings obtained using a bare dielectric.