Title: Influence of microstructure changes on corrosion resistance of super duplex stainless steel

Authors: A.M. Elhoud, N.C. Renton, D.A. Lasebikan, W.F. Deans

Addresses: School of Engineering, University of Aberdeen, Aberdeen, AB24 3UE, UK. ' School of Engineering, University of Aberdeen, Aberdeen, AB24 3UE, UK. ' School of Engineering, University of Aberdeen, Aberdeen, AB24 3UE, UK. ' School of Engineering, University of Aberdeen, Aberdeen, AB24 3UE, UK

Abstract: Effect of microstructure on pitting corrosion of super duplex was investigated in 3.5% NaCl solution at 90°C. The microstructures were controlled by applying two different cooling rates of water quench and air from the heat treatment temperatures of 1,000°C and 1,300°C. The amount of ferrite and austenite and other precipitates were measured using optical and image analyser. The results revealed that the ferrite percentage increased as the heating temperature increased to 1300°C. Metallographic results showed the presence of intermetallic phases. Back scattering analysis revealed presence of sigma (σ) and chi (χ) phase. The volume fraction of ferrite to austenite as well as the precipitation of harmful intermetallic phase during cooling process affected the corrosion resistance. Reformation of austenite during slow cooling from 1,300°C enhanced corrosion resistance while intermetallic precipitates promoted pitting damage and decreased pitting potential to more active values.

Keywords: heat treatment; super duplex stainless steel; volume fraction; austenite; ferrite; sigma phase; chi phase; corrosion resistance; microstructure; pitting corrosion; metallography; intermetallic phase; cooling.

DOI: 10.1504/IJMMP.2010.032500

International Journal of Microstructure and Materials Properties, 2010 Vol.5 No.1, pp.39 - 51

Published online: 04 Apr 2010 *

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