Electron beam hardening of nanobainitic steel

Abstract

Nanobainitic steels with high Si content are very promising materials due to the very favourable combination of mechanical and functional properties. However, sometimes in order to achieve the required results, it is necessary to further increase the surface's layer hardness. One of the feasible methods of surface hardening is electron beam hardening. In this work, 30 × 20 × 150 mm blocks made of nanobainitic steel were hardened using a defocused oscillating electron beam. Two methods of surface hardening were used – with movement of the sample relative to the heat source and hardening using only beam oscillation. The obtained samples were then subjected to light microscopic and scanning electron microscopic microstructure analysis as well as Vickers hardness testing. The average hardnesses of all hardened samples were in the range of 641–681 HV0.1 which means the surface hardening resulted in a hardness increase in the range of 239–279 HV0.1. The occurrence of similar hardening depths and hardness values in specimens hardened by both methods was an interesting phenomenon that was observed. The amount of energy input needed to achieve similar results was up to 35% less for the method without specimen movement.