Envelhecimento térmico de metais de solda dissimilares da liga AWS ER NiCrMo-14 (Inconel 686)

• Ano de defesa: 2015
• Autor(a) principal: Silva, Yuri Cruz da
• Orientador(a): Silva, Cleiton Carvalho
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Palavras-chave em Português: Ciência dos materiais; Ligas de níquel; Soldagem
• Link de acesso: http://www.repositorio.ufc.br/handle/riufc/12741

Nickel based alloys are highly recommended to oil industry due to its mechanical properties and corrosion resistance. The Inconel 686 alloy as-welded had its microstructure and mechanical properties studied in several works in Welding Engineering Laboratory of the UFC (Federal University Ceará). However, there is no known scientific studies regarding to the effects of thermal aging on the microstructure of this given alloy and its corrosion resistance. This study examines the AWS ER NiCrMo-14 (Inconel 686) alloy in a way that it was TIG welded using cold wire feed and aged at temperatures of 650 ° C and 950 ° C for 10, 50, 100 and 200 hours, with the objective to analyze the microstructure formed after aging treatment and its consequences in corrosion resistance. The ageing treatments caused a significant precipitation at both temperatures. In the treatment at 650 ° C there was a needled precipitation, of P or µ phases rich in molybdenum, around larger precipitates. In the sample of 950 ° C it was not observed the same precipitation as cited above, however, also presented an intense precipitation up to 13.82%. The precipitates were characterized by X-Ray diffraction (XRD) and Scanning Electronic Microscopic (SEM), Transmission Electronic Microscope (TEM), selected area electrons diffraction (SAD) and Energy Dispersive Spectroscopy (EDS). At the 650°C samples, it could be possible to identify, by using X-Ray diffraction, both M3C2 and M7C3 type carbides, μ and P phase. By using electron diffraction P phase was identified. At the 950°C treated samples, it could be possible to identify, by using X-ray diffraction and electron, the same stages that has been told above, except for the carbide M23C6 type. At this type, plaques were formed close to the interface with the base metal due to carbon migration from base metal (ASTM A36 Steel) to the nickel alloy and to the high temperature, which favors its formation. The precipitation had a great influence on the corrosion resistance of the samples. The alloy has been subjected to the immersion corrosion test according to ASTM G48 C method and anything samples had fail in temperature of 40 °C