Microstructure and hardness of electron beam molten surface of DSX40M alloy

Electron beam (EB) surface melting technique is becoming popular in nuclear, chemical and aerospace industries due to its large penetration depth and high cooling rate. Supercooling of the localized area helps to achieve non-equilibrium phases as well as a fine microstructure. EB surface melting of DSX40M, containing SiC, is carried out to improve the thermal stability and erosion resistance. Microstructure of the EB molten surface of alloy with and without the SiC is characterized with scanning electron microscope (SEM) having an energy dispersive system (EDS) as an attachment. During EB melting the SiC dissociated partially, interacted with the liquid alloy and resulted in different non-equilibrium phases like Si-rich eutectic, Co3Si, σ and α during solidification. Maximum hardness is achieved in electron beam molten zone (EBMZ) having columnar dendritic structure. Hardness of the molten zone (MZ) without SiC is lower than as-received alloy.