Date of Award
Fall 1967
Document Type
Thesis - Restricted
Degree Name
Master of Science (MS)
Department
Mechanical Engineering
First Advisor
Jansen, Richard J.
Second Advisor
Blumenthal, Robert N.
Third Advisor
Hirthe, Walter
Abstract
Austenite reversion and stabilization in 18% nickel maraging steels has recently become of practical significance with the increasing application of these alloys to high temperature service, welded structures and cold formed parts. A number of investigations have been carried out to determine the percentage of stable austenite present after elevated temperature exposure, but little data is available on the microstructural changes which occur during reversion and the effects of reversion on mechanical properties. High and low temperature impact, and room temperature hardness and tensile tests, along with microstructural studies were conducted on an 18% nickel 250 grade maraging steel which had been aged for times ranging from 1 minute to 9 weeks at temperatures between 700 and 1300°F. The test specimens were cut from a 1/2 " thick hot rolled plate that had initially been solution treated at 1500°F. It is shown that austenite reversion takes place more rapidly as time at temperatures above 900°F is increased. A maximum in the amount of stable reverted austenite was found after aging for 1 hour at 1200°F. Small quantities of reverted austenite have little effect on mechanical properties. Results are consistent with the view that stable austenite is formed by a diffusion reaction. In addition, other phases form as a function of aging time and temperature and a qualitative model has been proposed to explain the sequence of transformations.
Recommended Citation
Schmitt, Joseph J., "The Kinetics of Austenite Reversion in An 18% Nickel (250 grade) Maraging Steel and Its Effect on Mechanical Properties" (1967). Master's Theses (1922-2009) Access restricted to Marquette Campus. 4093.
https://epublications.marquette.edu/theses/4093