Banca de DEFESA: FRANKLIN LEMOS DA COSTA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : FRANKLIN LEMOS DA COSTA
DATE: 01/12/2022
TIME: 13:30
LOCAL: Virtual
TITLE:

Cyclic and isothermal high temperature oxidation of ferritic stainless steel AISI 439

KEY WORDS:

High temperature oxidation, Stainless steels, Characterization, AISI 439.

PAGES: 134
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Metalurgia Física
SPECIALTY: Corrosão
SUMMARY:

High temperature oxidation processes occur in different types of machines and equipment in the most varied fields of activities, in which stainless steels are used. Therefore, it is important to study and characterize the oxide layers formed and the mass variations that occur during the oxidation of these materials. Ferritic matrix stainless steels appear as a lower cost alternative to austenitic steels for high temperature applications. In this way, the present work will present an analysis of the isothermal and cyclic oxidation in high temperature of the ferritic stainless steel AISI 439. Studies have shown that the initial surface finish of the sample can have an important effect on the oxidation kinetics and on the adhesion of the oxide film. Therefore, in order to evaluate the effect of roughness on the behavior of the oxidation kinetics of this alloy, two different surface finishes were used. Half of the samples were sanded with silicon carbide sandpaper to #600 granulometry and the other half remained with a factory surface finish (laminate) on the faces. The isothermal and cyclic oxidation tests were carried out at temperatures of 750, 850 and 950 °C, in a time interval of up to 100 hours or cycles. The thermal cycles consisted of heating and holding for 1 hour at maximum temperature, followed by cooling for 10 minutes. The microstructure and chemical composition of the oxide layers formed were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray Diffraction (XRD). The alloy showed parabolic oxidation kinetics at the three test temperatures for the two surface finishes evaluated, which indicates the presence of an oxide film withprotective characteristics. However, the surface with greater roughness (laminate) showed less tendency to detachment. The oxides Cr2O3, TiO2 and MnCr2O4 were identified in the XRD analyzes for the two surface conditions evaluated.

BANKING MEMBERS:
Presidente - 1049564 - ARTUR MARIANO DE SOUSA MALAFAIA
Interno - 1877285 - ROBSON BRUNO DUTRA PEREIRA
Externo à Instituição - TARCISIO REIS DE OLIVEIRA