The microstructure of Ta alloying layer on M50 steel after surface alloying treatment induced by high current pulsed electron beam

In this research, the tantalum was chosen to be an alloying element into the surface layer of M50 steel to explore the microstructure after surface alloying treatment by high current pulsed electron beam. Different thickness of Ta films were deposited onto the M50 steel by DC magnetron sputtering before irradiation and the morphology of surface and cross section after surface alloying treatment were observed. The microstructure of alloying layer was investigated by X-ray diffraction and transmission electron microscope. The results revealed that alloying layer could be divided into three layers. The top layer was composed of δ-Fe phase with dendritic and small hollow spherical structure due to the segregation of alloying elements especially Ta. Some large spherical and a few dendritic microstructures could be observed at the second alloying layer; while there was only lath martensite microstructures at bottom of alloying layer.