Date

5-1-2018

Document Type

Thesis

Degree

Master of Science

Department

Materials Science and Engineering

First Adviser

DuPont, John N.

Abstract

The stress relief cracking (SRC) susceptibility of a range of austenitic and ferritic alloys was tested using Gleeble® based test procedures. The tests were developed to study the effect of post weld heat treatment (PWHT) temperature and cold working on the SRC susceptibility. Six susceptibility parameters were identified from the test results (ductility, percentage stress relaxed, hardness increase at fracture, failure time, fracture mode and extent/type of secondary cracks below the fracture). The susceptibility parameters were integrated with concepts of Risk Priority Number (tool in 6-Sigma) to develop an SRC susceptibility index. Sensitivity analysis of the methodology was done to ensure its robustness. The PWHT temperature of highest SRC susceptibility for ferritic alloys was observed to be 600°C while that for austenitic alloys was 800°C. Using the susceptibility index, the SRC propensity of all the alloys was divided into three categories (highly susceptible, moderately susceptible and resistant). The newly proposed test procedure and SRC susceptibility index provide a robust approach for studying and ranking the SRC susceptibility of engineering alloys. Post-test microstructural characterization of the SRC samples provided insight into the cracking mechanisms.

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