Gradient Furnace Study of Kinetics of the Aging Behavior of Four Commercial Grades of Maraging Steel
Date of Award
Spring 1969
Document Type
Thesis - Restricted
Degree Name
Master of Science (MS)
Department
Civil, Construction, and Environmental Engineering
Abstract
Gradient furnace techniques were used to determine the aging behavior and austenite reversion in four 18% Niokel grades of commercially available maraging steels. The grades investigated were 18 Nickel (200), (280), (300), and (350). Aging times ranging from 3/4 to 100 hours in a 600 degree-1800 degree F range of temperatures were employed in this investigation. The kinetics of aging behavior of the different grades were determined by hardness and tensile properties. In addition, optical, electron microscope, and electron microprobe investigations were performed to further identify the structures present. It ls postulated that three time-temperature dependent reactions take place in the aging of maraging steels. These reactions proceed to completion as the aging temperature is increased at constant time, or as the time is increased at constant temperature. The first reaction is that of precipitation hardening of the martensitic structure. The second reaction is that of overaging martensite and formation of reverted austenite. This reverted austenite results in a decrease in hardness and strength and an increase in ductility. The third reaction results in the formation of unstable austenite thru homogenization of the stable austenite. This unstable austenite transforms to martensite upon cooling to room temperature. In addition, the third stage appears to result in embrittlement of the steel since re-aged martensite exhibits lower ductility.
Recommended Citation
Rodriquez, Reynel J., "Gradient Furnace Study of Kinetics of the Aging Behavior of Four Commercial Grades of Maraging Steel" (1969). Master's Theses (1922-2009) Access restricted to Marquette Campus. 5490.
https://epublications.marquette.edu/theses/5490