[en] With everyday advancement in laser cladding technology, hard-faced materials have been considered as excellent candidates for tribological applications. In this study, Co–Ni intermetallics were synthesized on Ti–6Al–4V substrates using a 3 kW Rofin Sinar Ytterbium laser. Effect of the relationship between the laser parameters: powder composition, laser scan speed and laser power on the hardness values and tribological resistance of the coatings were studied. Microstructural examination and analysis were performed on resultant coatings using scanning electron microscope equipped with energy dispersive spectrometer. The coatings exhibited a good metallurgical bonding between the coatings and the substrate. Microhardness test was conducted on the coatings while the tribological behaviour of these coatings were also observed under a load force of 100 gf. The relationship between the microhardness and wear depth showed a tremendous benefit of the coatings to Ti–6Al–4V surfaces during abrasion. Phase analysis, using x-ray diffractometry, showed newly developed structures which may account for the increased microhardness values of the coatings as well as enhanced wear resistance. (paper)

[en] Heat transfer in materials during laser material processing serves as a key indicator to existing phases in the material, which governs the mechanical and chemical properties of the material during service. Without the knowledge of the property and behaviour of a material under service, loss of lives and values may be inevitable. This study presents the numerical modeling of the effect of laser parameters on the nature of phases present on the surface of Ti-6Al-4V alloy via heat transfer phenomenon. COMSOL 5.3a software was used to create a model of Ti-6Al-4V substrate, subjected to laser radiation during laser surface cladding. Boundary conditions were applied to the surfaces of the block samples while temperature distribution was measured with set boundary probes. Isothermal plots revealed that the material heating from the free surface was not sufficient enough to develop a large zone of phase change along the depth of the substrate. This was related to the high cooling rate of laser cladding. (paper)

[en] 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.

[en] The corrosion behavior of titanium alloys when used for various dynamic offshore components has been a major concern of titanium drilling risers in deepwater energy extraction. A way of achieving specified requirement is the development of coatings suitable to protect the base material against corrosion. In this work, laser cladding technique which is known as a leading edge due to its distinctive properties and outcomes was used in synthesizing Co-based powder on titanium alloy. The processing parameters used were laser power of 900W; scan speed of 0.6 to 1.2 m/min; powderfeedrate1.0g/min;beamspotsize3mm;gasflowrate1.2L/min.The effects of cobalt addition and laser parameters on corrosion behavior of laser clad Ti6AL4V coating in 0.5M sulfuric medium were investigated using linear potentiodynamic polarization. The changes in microstructure and corrosion behavior were analyzed using scanning electron microscopy (SEM) while the X –ray diffraction (XRD) indicates the intermetallics in the coatings. Results showed that the coatings displayed good metallurgical bonding with dendritic formations between the coatings and the substrate. The anodic current density increased with lower scan speed. However, the corrosion current densities of laser-clad samples were lower than Ti6Al4V alloy. (paper)