Dislocation Density Measurements from x-ray Diffraction of Austenite and Ferrite Phases in Superduplex UNS S39274

Abstract

Superduplex stainless steels (SDSSs) have high mechanical and corrosion resistance. Those properties are due to the biphasic microstructure formed by ferrite and austenite in similar proportions. Oil and gas companies use a cold-worked seamless tube manufactured in SDSS in oil country tubular goods applications. However, the understanding of how the cold work influences the dislocation density in each one of the SDSS phases is unclear. In this work, a cold-worked SDSS W-alloyed was investigated. Samples in as-received condition (AR-CW) and solution thermal treated at 1050, 1100, and 1150 °C were analyzed using XRD. Additionally, the AR-CW sample was characterized in TEM. The dislocation density was measured using Williamson & Smallman model, which uses the crystallite size and lattice microstrain as input parameters. Those parameters were calculated using different models: Scherrer; Monshi–Scherrer; and Williamson–Hall. The cold work promotes a smaller crystallite size and a bigger lattice microstrain. The thermal treatment reduces the levels of dislocation density, and the increase in the treatment temperature results in higher dislocation density.