Various categories of defects after surface alloying induced by high current pulsed electron beam irradiation

High current pulsed electron beam (HCPEB) is an attractive advanced materials processing method which could highly increase the mechanical properties and corrosion resistance. However, how to eliminate different kinds of defects during irradiation by HCPEB especially in condition of adding new elements is a challenging task. In the present research, the titanium and TaNb-TiW composite films was deposited on the carburizing steel (SAE9310 steel) by DC magnetron sputtering before irradiation. The process of surface alloying was induced by HCPEB with pulse duration of 2.5 mu s and energy density ranging from 3 to 9 J/cm2. Investigation of the microstructure indicated that there were several forms of defects after irradiation, such as surface unwetting, surface eruption, micro-cracks and layering. How the defects formed was explained by the results of electron microscopy and energy dispersive spectroscopy. The results also revealed that proper energy density (similar to 6 J/cm(2)) and multi-number of irradiation (>= 50 times) contributed to high quality of alloyed layers after irradiation. (C) 2015 Elsevier B.V. All rights reserved.