INFLUENCE OF CEO2 ADDITION AND SCANNING SPEED ON MICROSTRUCTURE AND TRIBOLOGICAL BEHAVIOR OF LASER-CLAD Ti-Co REINFORCED COATINGS ON Ti-6Al-4V ALLOY

Abstract

Ti-6Al-4V alloy is restricted in industrial application as a result of its relatively low hardness and poor tribological properties. However, the limitations associated with Ti-6Al-4V in severe tribological conditions can be improved via laser cladding technique. In this study, the influence of rare earth oxide (CeO[Formula: see text] addition on microstructure, hardness and tribological behavior of laser-clad titanium–cobalt-based coatings on Ti6Al4V alloy was investigated. The optimized parameters used for laser depositions are laser power 900[Formula: see text]W; beam spot size 3[Formula: see text]mm; powder feed rate 1.0[Formula: see text]g/min; gas flow rate 1.2[Formula: see text]L/min while laser scan speed was varied at 0.6[Formula: see text]m/min and 1.2[Formula: see text]m/min. Thereafter, the coating morphology as well as wear mechanism of the coatings of CeO2 particles (5–10[Formula: see text]wt.%) dispersed in TiCo matrix were investigated via scanning electron microscope (SEM) equipped with energy dispersed spectrometry (EDS), whereas the intermetallic phases present in the coatings were observed using Philips PW1713 X-ray diffractometer (XRD). Furthermore, the micro-hardness values of the coatings were recorded while wear test was carried out using a reciprocating set up (UMT-2 — CETR tribometer). Results revealed that the incorporation of CeO2 particles into the melt pool influenced the morphology of the coatings, thus resulting in finer cellular dendrites, homogenous and strong metallurgical bonding between the laser cladded coating and the substrate. The phases revealed various fractions of interdendritic compounds (CeCo2, Ni3Ti, Co2Ti, CoTi, Al2O3, TiO, AlTi3, and Ce2O[Formula: see text] dispersed within the coating matrix, thus resulting in 2.68 times improvement on the surface hardness and 47.4% reduction in friction coefficient in comparison with Ti-6Al-4V alloy.