Award Date

1-1-2007

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

First Committee Member

Ajit K. Roy

Number of Pages

160

Abstract

This investigation was focused on the evaluation of the tensile properties and environment-assisted degradations of martensitic T91 grade steels as a function of silicon (Si) content. The tensile strength and ductility was gradually enhanced at room temperature with an increase in Si content from 0.5 to 1.5 weight percent (wt%). However, the strength was reduced with 2.0 wt% Si, while showing increased ductility due to work-softening. Under irradiated conditions, all tested materials exhibited hardening, the extent being more pronounced at longer irradiation times. The corrosion potential became more active (negative) with increasing temperature in polarization experiments in an acidic solution. The stress corrosion cracking (SCC) tendency, in terms of measurable parameters in a similar environment, was enhanced at elevated temperatures, showing a detrimental effect of 2.0 wt% Si. The generation and entrapment of hydrogen at 30 and 60°C, resulting from cathodic applied potentials, adversely affected the SCC susceptibility of the tested alloys. The crack-growth in double-cantilever-beam specimens was enhanced at higher initial stress intensity factor values, showing increased crack-growth in steel with 2.0 wt% Si. The corrosion rate was gradually reduced with increased Si content up to 1.5 wt%, followed by an appreciable increase at 2.0 wt% Si. A combination of intergranular and cleavage brittle failures of different extent was observed in the tested specimens, irrespective of the Si content.

Keywords

Content; Corrosion; Corrosion; Deformation; Degradation; Different; Environmental; Environmental Degradation; Grade; Silicon; Silicon Content; Steels; Steels Tensile; Tensile Deformation

Controlled Subject

Mechanical engineering; Materials science

File Format

pdf

File Size

8007.68 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

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