The effect of tempering and aging on a low activation martensitic steel
- PDF / 5,092,103 Bytes
- 9 Pages / 594 x 774 pts Page_size
- 90 Downloads / 203 Views
I.
II.
INTRODUCTION
FERRITIC and
martensitic steels are being considered as candidate materials for the first wall of fusion reactors because of their swelling resistance and their mechanical properties. A more recent requirement for these steels is for their radioactivity to decay to relatively low levels within 100 to 500 years. To reach this goal, alloying changes in the current steels must be made. The steel of this study, L9, was provided by Battelle Pacific Northwest Laboratories. The steel is a 12 pct chromium alloy which is designed to be fully martensitic when aircooled. The compositions of L9 and HT-9 are shown in Table I; HT-9 is another 12 pct chromium martensitic steel which is being considered for fusion reactor use. The carbon content of L9 was reduced, and to achieve the desired decay in activation, the nickel and molybdenum were eliminated. The tungsten content of L9 was increased to replace the molybdenum which is needed for high-temperature strength. The tungsten level was held at 1 pct to avoid intermetallic formation. Nickel and carbon are austenite stabilizers, and their loss was compensated for by increasing the manganese content. Although neutron irradiation results on L9 have been published, ~ there has not been a study of the response of this steel to heat treatment. In this work, this omission is addressed.
R.D. GRIFFIN, Research Assistant, R.A. DODD, Professor, and G.L. KULCINSKI, Head, are with the Fusion Technology Institute, Department of Nuclear Engineering and Engineering Physics, University of Wisconsin-Madison, Madison, WI 53706. D.S. GELLES is Staff Scientist, Structural Materials, with Battelle Pacific Northwest Laboratory, Richland, WA 99352. This paper is based on a presentation made in the symposium "Irradiation-Enhanced Materials Science and Engineering" presented as part of the ASM INTERNATIONAL 75th Anniversary celebration at the 1988 World Materials Congress in Chicago, Illinois, September 25-29, 1988, under the auspices of the Nuclear Materials Committee of TMS-AIME and ASM-MSD. METALLURGICAL TRANSACTIONS A
EXPERIMENTAL PROCEDURE
The alloy was received in the rolled condition and was first normalized at 1000 ~ for 20 hours followed by an air-cool to room temperature, after which it was reheated to 1100 ~ for 10 minutes and allowed again to air-cool to room temperature. To determine the tempering response of the steel, it was held for 2 hours at 400 ~ 500 ~ 600 ~ 700 ~ 800 ~ and 900 ~ and for 24 hours at 500 ~ and 700 ~ Steels which were aged first received a 2-hour temper at 700 ~ and then were aged for 1000 and 5000 hours at 365 ~ 420 ~ 520 ~ and 600 ~ Optical metallography, microhardness, and transmission electron microscopy (TEM) were used to characterize the heat-treated steel. IlL
RESULTS
The steel formed a fully martensitic structure when air-cooled, as shown in the optical images of the rolled, normalized, and normalized and tempered steel (Figure 1). In many of the images, prior austenite grain boundaries are visible. The average size of these grains was
Data Loading...
