Laser Cladding and Characterization of Ni–SiC–ZrB2 Cermet Coatings on Ti–6Al–4V for High-Temperature Applications

Abstract

High-temperature ceramic–metal (cermet) coatings are highly viable in engineering applications involving ablative influence of hot environments. Thus, the synthesis of two different compositions (75Ni:20SIC:5ZrB2 and 70Ni:20SiC:10ZrB2) of Ni–SiC–ZrB2 cermet coatings on Ti–6Al–4V (Grade 5) alloy using laser cladding technique was successful in the present study. Phase analysis was conducted on the coatings to investigate the existing phases using x-ray diffraction, while scanning electron microscope (SEM) equipped with energy-dispersive spectrometer (EDS) was used to examine microstructural morphology of the cermet coatings. Wear and oxidation tests were performed on both the as-received sample and the laser cladded samples with the use of a CERT UMT-2 ball-on-disk reciprocating tribometer and PerkinElmer TGA 4000 thermal analyzer, respectively. High diffraction peaks of ZrSi2, Ni3Ti, and Ni3B indicated micromigration and in situ reactions among elemental constituents between the coatings and the substrate. Friction coefficients and microhardness values of the coatings proved enhanced tribological and hardness properties in comparison with the Ti–6Al–4V substrate, accordingly. After oxidation, the as-received sample revealed oxide phases of TiO2, SiO2, and Al2O3, while the oxidized coatings showed protective oxides of ZrO2, NiO, Ni3TiO5, and ZrSiO4. Although the coatings were characterized with microcracks and intense dissolution of SiC particles, the coatings showed good metallurgical bond with the substrate.