Avaliação microestrutural de cordão soldado a laser Utilizando mistura metal-cerâmica (uns s32304-tib2)

• Ano de defesa: 2024
• Autor(a) principal: Xavier, Gabriel Correa
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal do Espírito Santo; BR; Mestrado em Engenharia Mecânica; Centro Tecnológico; UFES; Programa de Pós-Graduação em Engenharia Mecânica
• Palavras-chave em Português: Aço inoxidável duplex; Soldagem a laser; Diboreto de titânio; Engenharia Mecânica
• Link de acesso: http://repositorio.ufes.br/handle/10/18222

Duplex stainless steels (DSS) are widely used due to their good corrosion resistance and high mechanical strength, when compared to austenitic stainless steels, especially in corrosive environments such as nuclear, chemical, petrochemical, and offshore oil and gas industries. This class of materials requires careful control of cooling rates during welding, both to maintain the appropriate ferrite-austenite ratio and to prevent the formation of detrimental precipitates. The high concentrated energy released during laser welding is advantageous in producing limited heat-affected zones and high cooling rates, which hinder the formation of undesirable precipitates. With the aim of combining the good mechanical characteristics found in DSS with low density and high process yield found in ceramic compounds, there is a strong industry trend towards producing powder metallurgy sintered stainless steel composites. Therefore, the objective of this dissertation is to evaluate the properties of laser-welded joints in UNS S32304 duplex stainless-steel sheets using a mixture of the same steel powder with varying proportions of titanium diboride ceramic. Several techniques, such as X-ray diffraction, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), microindentation, and microtomography were employed to characterize the microstructure and hardness of the samples welded with the manufactured powder. The results revealed a deviation from the ideal ferrite-austenite ratio in welded joints when TiB2 ceramic was introduced, primarily attributed to the formation of titanium nitride (TiN). Microhardness tests indicated an increase in hardness in the fusion zone as a function of TiB2 content in the samples and due to the presence of the formed titanium nitride. Furthermore, microtomography revealed improved weld bead homogeneity and a narrower fusion zone in samples containing TiB2, suggesting enhanced weld quality. These findings highlight the potential of TiB2 ceramic as an effective reinforcement in improving the microstructural and mechanical properties of laser-welded DSS joints, promising advancements in the manufacturing of corrosion-resistant materials for various industrial applications.