Novel wear resistant carbide-laden coatings deposited by powder-suspension hybrid plasma spray: Characterization and testing

Thermal spraying with a hybrid powder-suspension feedstock presents a novel approach to conveniently realize coatings with unusual chemistries and unique microstructures. In this study, coatings were deposited by simultaneous spraying of T-400 (Tribaloy-400) powder and Cr3C2 suspension with varying relative feed rates. For comparison, pure T-400 coating was also deposited using powder feedstock via atmospheric plasma spray (APS) route to assess the role of incorporating a hard, finely distributed carbide phase in the coating. SEM (Scanning electron microscopy)/EDS (Energy-dispersive X-ray spectroscopy) investigation of the hybrid coatings revealed a lamellar microstructure with distributed fine carbides. XRD (X-ray diffraction) analysis of the feedstock and hybrid coatings showed the presence of original feedstock constituents, along with some oxides of chromium, in the deposited coating. Hardness measurements on the as-sprayed coatings indicated higher hardness in hybrid coatings than in the pure T-400 coating. The deposited coatings were subjected to scratch testing on polished surfaces as well as on polished cross sections. The scratching response of the coatings was examined by SEM analysis. Results demonstrated that the hybrid coatings possess excellent scratch resistance, superior compared to the pure T-400 coating, which is promising for extending the durability of engineering components operating under severe wear conditions. This was confirmed by abrasion test results which established the superior wear resistance of hybrid coatings. The above hybrid approach is easily extendable to other material systems and can have important implications in the realization of next-generation wear resistant coatings.