Comportamento microestrutural e de fluência do Inconel 718 após tratamento térmico de duplo envelhecimento
Creep and microstructural behavior of Inconel 718 after double aging heat treatment
Fabrícia Assis Resende Gonçalves, Renata Jesuina Takahashi, Danieli Aparecida Pereira Reis
Resumo
Inconel 718 é uma liga à base de níquel que é principalmente utilizada em aplicações de alta temperatura devido às propriedades mecânicas e à tolerância a condições severas de trabalho. As ligas Inconel podem ter suas propriedades mecânicas melhoradas com a aplicação de tratamentos térmicos pela precipitação de fases endurecedoras. Neste trabalho objetivou-se estudar do comportamento mecânico e microestrutural da superliga Inconel 718 após ensaio de fluência. Comparou-se os resultados da liga sob as condições homegeneizada (como fornecida) e após tratamento térmico de duplo envelhecimento composto pelas etapas de solubilização (1095 °C durante 1 hora) e tratamento térmico (955 °C/1 h seguido por 720 °C/8 h e 620 °C/8 h). Os ensaios de fluência foram realizados no modo de carga constante de 625 MPa e a temperatura em 650, 675 e 700 °C. Os corpos de prova de fluência foram avaliados pelas técnicas de caracterização de difratometria de raios X, microscopia eletrônica de varredura e análise de dureza. Os resultados obtidos indicaram que as amostras que sofreram o tratamento térmico de duplo envelhecimento apresentaram maior resistência mecânica devido, possivelmente, a precipitação de fases endurecedoras como a fase γ’ (Ni3 Al) e fase γ” (Ni3 Nb) formadas durante o tratamento térmico da liga. Além disso, o ganho de resistência foi comprovado pelo aumento dos valores da dureza e pelo aumento no tempo de fratura dos ensaios de fluência.
Palavras-chave
Abstract
Inconel 718 is a nickel-based alloy that is mainly used in high-temperature applications due to its mechanical properties and tolerance to severe work environments. Inconel alloys can be their mechanical properties significantly improved with the execution of heat treatments to precipitate hardening phases. This work aimed to study the mechanical and microstructural behavior of the Inconel 718 superalloy after creep test. The results of the alloy were compared under homogenized conditions (as received) and after heat treatment of double aging composed by solubilization (1095 °C for 1 hour) and heat treatment (955 °C/1 h followed by 720 °C/8 h and 620 °C/8 h). The creep tests were executed in in the stress range of 625 MPa in a constant load mode at 650, 675 and 700 °C. The creep specimens were evaluated using X-ray diffraction, scanning electron microscopy and hardness analysis techniques. The results indicated that the samples of heat treated showed greater mechanical resistance, possibly due to the precipitation of hardening phases such as the γ’ (Ni3 Al) and γ” (Ni3 Nb), phases formed during the double aging heat treatment. In addition, the strength gain was proven by the increase in hardness and the increase in fracture time of creep tests.
Keywords
Referências
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Submetido em:
17/06/2021
Aceito em:
21/09/2021
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