Avaliação da resistência mecânica de liga ti-6al-4v soldada com processos laser e plasma de uso odontológico

Abstract

There is limited information in existing literature regarding the accomplishment of Ti-6Al-4V joints plasma and laser welded in prefabricated bars in different diameters. Therefore the aim of this study was evaluate the mechanical resistanceof TI-6AL-4V alloyin different diameters(2.5, 3, 4 e 5mm) submitted to the processes of plasma and laser welding by means of tensile test and Finite Element Models.Forty-five dumbbell-shaped rods (n=5) with central diameters of 2.5, 3,4 and 5 mm were created from Ti-6Al-4V prefabricated bars: CG(Control group) with 3 mm diameter, constituted by intact bars and PL2.5, PL3, PL4 and PL5 groups with 2.5, 3, 4 and 5 mm diameters submitted to plasma welding processand L2.5, L3, L4 and L5 groups with 2.5, 3, 4 and 5 mm diameters submitted to laser welding process. Theplasma welding process was executed using current of 10 Aand pulse of 3 ms and laser welding was executed usingvoltage of 365 V e pulse of 9 ms and the focus and frequency were calibrated at 0. The specimens were tested for tensile strength test until fracture and the percentage of elongation was obtained.Fractured samples were analyzed in stereomicroscope and the welded areas percentage was calculated. The most representative images were taken by tabletop scanning electron microscope in increases of 500 and 1200x. The results were evaluated by analysis of variance (ANOVA) and subsequently using Dunnet test to compare test groups to control group and the Tukey test to compare means of the test groups. Pearson and Spearman\'s correlation tests were applied for comparison of the parameters analyzed.The finite element models were developed in a Workbench environment with boundary conditions simulating a tensile test.Analyzing the tensile strengthand the welded area percentage there were statistical difference between groups(P > .05). Most of specimens of the test groups were fractured on the welded area. The control group showed higher values to tensile strength than test groups. Analyzing the percentage of elongation there was statistical difference between control group and test groups but not between test groups. There was a positive correlation between welded area percentage and tensile strength in all the specimens in the test groups and a negative correlation between these parameters and the diameters of the specimens.It was concluded that the diameter of 2.5 mm and 3.0 seem to be the best option for joining prefabricated rods for use in prosthetic frameworks for both plasma and laser welding, and the plasma welding seems to be an alternative of laser welding equipment, presenting no significant statistical differences between them for each diameter.