RESUMO
This study investigated the metallurgical, mechanical properties and quality of coatings fabricated by direct laser metal deposition (DLMD) on Ti-6Al-4V, which were affected by the DLMD optimized process parameters. A 3-kW continuous wave ytterbium laser system (YLS) attached to a KUKA robot was used for the process. An analysis was conducted to determine the quality of the coatings in terms of hardness and wear resistance. Variables such as the time of interlayer deposition, thickness of the substrate, the initial temperature of the substrate, and the number of deposited layers were also investigated. The independent/collective effect that each process parameter had on the metallurgical and mechanical properties of the deposited Ti-6Al-4V were made clear when the processing parameters were varied. Minute pores/defects that significantly affect the metallurgical and mechanical properties of clads were also identified. The results obtained from the designed experiments showed that the depth of Heat Affected Zone (HAZ) was inversely proportional to the thickness of the substrate; as the thickness of the substrate was increased, the HAZ depth decreased. Moreover, the intensity of the laser power also affects the HAZ depth. In addition, it was discovered that the initial conditions of the substrate at room temperature also affected the coatings in relation to pre-heated conditions. The analysis conducted in identifying and quantifying the porosity showed indication that the factors such as scanning speed, laser power and powder feed rate had a predominant influence on the porosity. The grain form and structure as well as the mechanical properties of the cladded layer were significantly affected by the optimized process parameters of DLMD process. The parameters investigated had a significant impact on the hardness and wear resistance performance. Furthermore, the results revealed that the highest hardness of one of the coatings was 1.97-times the substrate which had a hardness value of 302 HV. The outstanding wear resistance performance of Al-Si-Sn-Cu/Ti-6Al-4V composite coating is attributed to major hard intermetallic phases.
