Microstructural modification of plain carbon steels irradiated by high-energy electron beam
- PDF / 3,382,228 Bytes
- 11 Pages / 612 x 792 pts (letter) Page_size
- 41 Downloads / 143 Views
I.
INTRODUCTION
The microstructural modification of the steel surface can be achieved by various surface treatments such as flame hardening, induction hardening, and laser beam technique.[1,2] In addition to these techniques, high-energy electron beam irradiation is recently suggested as an attractive technique because it has exceptionally high thermal efficiency. When the high-energy electron beam generated by an accelerator hits steel samples, kinetic energy of electron beam is transformed directly to thermal energy. The electron beam irradiation can also create a number of lattice defects which might have an influence on the kinetics of phase transformation through increasing diffusivity, but which might not seriously affect the phase transformation behavior in steels because the time required for irradiation is too short. This can provide a very powerful heat source, which in turn can be applied to surface treatment, welding, and joining of structural materials.[3,4,5] Furthermore, it has many advantages such as homogeneous heating and cooling and continuous surface processing of very large structures or parts in air without serious surface oxidation.[6] Upon irradiation by high-energy electron beam, the temperature of the irradiated surface rises easily to high temperatures over the austenite range, and then drops quickly to room temperature since the temperature of the interior bulk material maintains constantly at room temperature. This temperature rise can be controlled by using irradiation parameters in a high-energy electron beam accelerator. If the irradiation is applied to a plain carbon steel, martensitic DONGWOO SUH, formerly Research Assistant, Center for Advanced Aerospace Materials, Pohang University of Science and Technology, is Postdoctoral Research Associate, Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139-4307. SUNGHAK LEE, Associate Professor, Center for Advanced Aerospace Materials, and YANGMO KOO, Associate Professor, Department of Materials Science and Engineering, are with Pohang University of Science and Technology, Pohang, 790-784, Korea. Manuscript submitted April 16, 1996.
METALLURGICAL AND MATERIALS TRANSACTIONS A
transformation in the surface region can take place, so that the surface hardening can be achieved. The present article reports on a study of high-energy electron beam irradiation of two plain carbon steels and clarifies the role of the microstructural factors that govern hardness of the steels. Specifically, the effects of carbon content and processing variables on hardness were explored and correlated with corresponding microstructural parameters, such as the amount of martensite and grain size, and were then discussed with respect to possible phase transformation for hardening of the steels. Heat input and temperature variation during irradiation were also examined using a thermal simulation test and a heat-transfer model to find the correlation of the irradiation parameters and the microstructures. II.
EXPE
Data Loading...
