Degree Type

Dissertation

Date of Award

1982

Degree Name

Doctor of Philosophy

Department

Materials Science and Engineering

Abstract

Smooth-bar and notched-bar tensile specimens of bainitic 2 1/4 Cr-1 Mo steel were exposed with and without an applied stress to argon gas or to a coal slurry-H(,2) environment for various conditions of time, temperature and pressure. Room temperature mechanical properties determined after each coal slurry-H(,2) exposure were compared to those of like samples exposed to the same conditions in argon. The coal slurry exposures produced very little change in the room temperature mechanical properties even after 1000 hours at temperatures as high as 426(DEGREES)C and total pressures of 27.6 MPa;Corrosion samples were exposed in both the liquid phase and the gaseous phase above the coal slurry-H(,2) environment. Scale growth rates, electron microprobe analyses and X-ray analyses of the scale region were obtained;Smooth-bar and notched-bar tensile specimens of normalized and tempered (bainitic) 2 1/4 Cr-1 Mo steel were exposed to hydrogen gas at 5.2 to 27.6 MPa in the temperature range from 482(DEGREES) to 593(DEGREES)C. Exposed samples were in three conditions: unloaded, with an applied load, or lightly prestrained. Applied stress, plastic deformation and increasing exposure times all lowered the temperature, at any given pressure, for the formation of hydrogen attack bubbles. The results have been plotted on Nelson Curve coordinates;Fatigue crack growth tests were conducted on normalized and tempered (bainitic) 2 1/4 Cr-1 Mo steel. Crack growth rates were determined for near threshold to intermediate growth rate regions at room temperature and 427(DEGREES)C. Testing was done in a partial vacuum, moist air, hydrogen and coal slurry gases. Crack growth rates for various hydrogen pressures were examined. The results suggest that corrosion products of the coal slurry gases may mitigate the tendency of hydrogen to enhance fatigue crack growth. Possible mechanisms are suggested;J integral tests were performed to determine JIC on normalizedand tempered (bainitic) 2 1/4 Cr-1 Mo steel. J values were obtainedfrom deep cracked compact tension specimens using single andmultiple specimen techniques. Testing was carried out in vacuum,argon, hydrogen and coal slurry gases at 427(DEGREES)C. Single specimentests were made using an electropotential crack growthmeasurement system described in detail. Values of J(,IC) for the singlespecimen tests are compared to those obtained from the multiple;specimen tests;('1)DOE Report IS-T-1024. This work was performed under ContractW-7405-Eng-82 with the Department of Oil, Gas, and Energy;

DOI

https://doi.org/10.31274/rtd-180813-5902

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Charles Martin Woods

Language

en

Proquest ID

AAI8224347

File Format

application/pdf

File Size

241 pages

Included in

Metallurgy Commons

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