MICROSTRUCTURAL MODIFICATION OF PLAIN CARBON-STEELS IRRADIATED BY HIGH-ENERGY ELECTRON-BEAM

The main objective of the present study is to analyze the microstructu ral modification of the surface hardened by the irradiation of high-en ergy electron beam in 0.18 pet C and 0.38 pet C plain carbon steels. S teel samples were irradiated using an electron accelerator (1.4 MeV), and the detailed microstructures of the irradiated surface were examin ed. Upon irradiation, the ferrite-pearlite structure near the sample s urface was changed to the dual-phase structure, i.e., ferrite and mart ensite, and fine particles or needlelike lamellae were observed in the ferrite/martensite interface. In order to investigate these complex m icrostructures as well as the martensitic transformation mechanism, th e simulation test, including thermal cycles of abrupt heating and quen ching, was carried out. The test results indicated that the irradiated surface was heated up to about 1100 degrees C and then quenched to ro om temperature, which was enough to obtain the surface hardening throu gh martensitic transformation. Thermal analysis of the irradiated surf ace was also carried out for systematic understanding of the microstru ctural modification in terms of the irradiation parameters such as bea m travel speed.