Date of Graduation

Spring 2016

Document Type

Honors Research Project

Degree Name

Bachelor of Science

Major

Corrosion Engineering

Research Sponsor

Dr. Rajeev Gupta

First Reader

Dr. Scott Lillard

Second Reader

Dr. Gregory Morscher

Abstract

High Pressure Torsion (HPT) is a materials processing method used to refine the grain size of metallic materials through the application of simultaneous axial and torsional strain. HPT is reported to result in nanocrystalline structure, which the current scientific literature suggests may improve the high temperature oxidation resistance by enhancing diffusion of solutes, particularly Cr, to the surface to form a protective external oxide scale. If oxidation resistance is improved, this possibly allows the use of 316L in oxidizing environments where more expensive alloys are typically used. However, the influence of grain refinement to nanoscale on various properties have been controversial and reported to be a strong function of the processing techniques used for the grain refinement. Therefore there is merit in studying the high temperature oxidation behavior of nanocrystalline alloys prepared by various processing routes and HPT in current study.

Nanocrystalline and conventional coarse-grained 316L samples were oxidized at various temperatures and their oxidation kinetics were determined by weight gain measurements at regular time intervals. The activation energies for the oxidation were estimated using an Arrhenius relationship. The resulting microstructures and scales were examined using scanning electron microscope (SEM) coupled with energy dispersive X-ray spectroscopy (EDXS). This study yields significant understanding about the influence of nanocrystalline structure and processing methods on the high temperature oxidation characteristics of a chromia forming alloy (SS316L).

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