masterThesis
Resistência ao desgaste, corrosão e sinergia do aço duplex UNS S32205 com e sem nitretação a plasma em baixa temperatura
Fecha
2018-09-25Registro en:
ROSA, Yamid Enrique Núñez de la. Resistência ao desgaste, corrosão e sinergia do aço duplex UNS S32205 com e sem nitretação a plasma em baixa temperatura. 2018. 120 f. Dissertação (Mestrado em Engenharia Mecânica e de Materiais) - Universidade Tecnológica Federal do Paraná, Curitiba, 2018.
Autor
Rosa, Yamid Enrique Núñez de la
Resumen
Duplex stainless steels have good resistance to wear and corrosion and are therefore
applied in the food, chemical and petrochemical sectors. In the latter, various components such
as risers, valves, shafts, propellers, rings are duplex steel pipes that are used in the transportation
of petroleum, working in aggressive conditions, in the presence of abrasive particles and chloride
ions, which together create an environment in which this steel can become brittle due to its
degradation. In order to improve the resistance of these stainless steels, it was proposed the
introduction of nitrogen by the thermochemical treatment of low temperature (380°C) plasma
nitriding performed in GrMaTS / UTFPR. The thermochemical treatment was carried out in a
reactor containing N2-H2 atmosphere for a time of 10 h, with previous cleaning treatment and
heating with Ar-H2. In this work, with the objective of evaluating the relationship between the
plasma nitriding of the UNS S32205 series duplex steel in the synergism that occurs due to wear
and corrosion, isolated tests of pure abrasion (without corrosion) were carried out in an
atmosphere environment controlled inside a closed box type glove box by means of a free ball
type tribometer. The pure corrosion tests (without abrasion) were carried out in 3.5% NaCl
solution in a potentiostat assisted electrochemical cell from the potentiodynamic polarization
technique. Subsequently, the strength of this material was evaluated for tribocorrosion containing
a combination of wear test and an electrolytic medium to promote corrosion. Subsequently, the
characterization of the surface was carried out using optical microscopy (OM), X-ray diffraction
(XRD), scanning electron spectroscopy (SEM-EDS) and Vickers microhardness tests. The
treatment of plasma nitriding promoted the formation of the metastable phase of expanded
austenite with a thickness of 3.0 ± 0.2 μm and a hardness of 1101.8 ± 179.9 HV0.05. It was
noticed that nitrided steel was improved because it presented less resistance to transfer and
greater potential of pite, greater resistance to pure wear, and verified that in the tribocorrosive
test that the mechanical and electrochemical processes interact with each other to increase
the overall wear process of materials. and finally that the magnitude of the synergism foreach of the study materials is implicitly related to the aggressiveness of the effect of the
medium on the material.