Efeito de múltiplos ciclos de solubilização sub-solvus delta e envelhecimento na microestrutura e propriedades mecânicas da superliga 718

• Ano de defesa: 2017
• Autor(a) principal: Oliveira, Alexandre de
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal do Rio de Janeiro; Brasil; Instituto Alberto Luiz Coimbra de Pós-Graduação e Pesquisa de Engenharia; Programa de Pós-Graduação em Engenharia Metalúrgica e de Materiais; UFRJ
• Palavras-chave em Português: Liga metálicas; Tratamentos térmicos; Microestrutura; Propriedades mecânicas; CNPQ::ENGENHARIAS::ENGENHARIA DE MATERIAIS E METALURGICA::METALURGIA FISICA::ESTRUTURA DOS METAIS E LIGAS
• Link de acesso: http://hdl.handle.net/11422/5944

The nickel based superalloy 718 was developed to meet the requisites of components for aircraft engines, due to its excellent creep resistance up to 650°C. During the maintenance of the engines, the components can be submitted to successive repair procedures, however the mechanical properties can be estimated solely during the project development. In order to understand the uncertainties during the repair procedures that can result in cost to the production chain, the present work aims to evaluate the evolution of the microstructure and the properties of tensile and hardness after being submitted to successive cycles of sub-solvus δ solution annealing (954°C/1h) and aging (760°C/5h + 649°C/1h). Forged and cast samples had its microstructures observed by optical and scanning electron microscopes with the identification of precipitates made by the morphologies. Grain size measurements, hardness measurements and tensile tests were performed. It was observed that δ precipitation at grain boundaries occurred, keeping a refined microstructure. However, there was a crescent evolution of the δ particles in volume and average size. As a consequence, a reduction of the Nb available to the formation of γ” occurred, the main hardening phase, evidenced by the reduction of the ultimate tensile strength, yield strength and hardness.