Effect of niobium in the phase transformation and corrosion resistance of one austenitic-ferritic stainless steel

Abstract

Austenitic-ferritic stainless steels containing 0.2% and 0.5% niobium were evaluated with respect to the microstructures, microhardness, pitting potential resistance, electrochemical impedance and wearing tests. Niobium is an alphagenic element and has a great influence on phase transformation of duplex stainless steels. In the present investigation, the samples were annealed at 1050 °C and aged at 850 °C to promote the formation of sigma phase. The pitting potential resistance and electrochemical impedance were evaluated in 3.5 % sodium chloride solution. The wear coefficients were calculated by micro-wear tests conducted using a fixed ball machine and aluminum oxide as abrasive. The results show that the niobium content lead to increase on Laves phase formation. This phase, in association with the sigma phase, causes a significant increase in the hardness and wear resistance with a decrease on corrosion resistance of the austenitic-ferritic stainless steels.

Caracterização microestrutural de um aço inoxidável austeno-ferrítico, por meio do software Factsage

“…Considerando as análises microestruturais nas figuras 1 e 2, as simulações computacionais das figuras 3 e 4 e o espectro de concentração da fase sigma na figura 5, é possível afirmar que, embora as simulações com o FactSage indiquem a presença das fases sigma e de Laves no aço, os resultados experimentais mostram apenas a primeira, após a solubilização seguida de envelhecimento. Laves pode ser formada com diferentes estequiometrias, tais como, Fe 2 Nb, Fe 2 Mo, Fe 2 Ti e outras, e é comum nos aços austeno-ferríticos modificados com nióbio (Itman Filho et al, 2014).…”

“…Uma fase interessante é a de Laves com estrutura hexagonal compacta que pode ser formada com diferentes elementos químicos, tais como, Cr 2 Nb, Fe 2 Mo, Fe 2 Ti, Fe 2 Nb. A precipitação ocorre na forma de ripas na matriz e está associada à fragilização da liga (Itman Filho et al, 2014;Zhu et al, 2023).…”

The hardness, microstructure, and pitting resistance of austenitic stainless steel Fe25Ni15Cr with the addition of tungsten, niobium, and vanadium

“…With the addition of Nb in the alloys, the hardness increase due to precipitation. Laves and sigma phases, associated with the niobium dissolved in matrix, increase the hardness of these steels [6].…”

Deposition of Ti-Based Thin Films on AISI 1020 Steel Substrates Using the Cathodic Cage Plasma Deposition Technique

“…Various materials such as stainless steel, low-carbon steel, and cast iron are used in automotive exhaust systems because of their thermal properties. However, they can corrode because the environment of the car exhaust system is very corrosive, as the exhaust gasses and condensation water contain harmful elements such as Cl -, SO 4 2-, SO 3 2-, HCO 3-, CO 3 2-and CH 3 COOH 1,7,8,[19][20][21][22][23][24] . These harmful elements affect air quality and can lead to asphyxiation accidents or long-term occupational diseases.…”