Characterization of electron beam modified surface of Zircaloy-4

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 Zircaloy-4, containing SiC, is carried out to improve the surface melting temperature, thermal stability and erosion resistance. The resulted microstructure and non-equilibrium phases are characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Zircaloy-4 is successfully surface hardened by EB melting. The surface hardening can be attributed to both Zr-rich silicides as well as the small size secondary SiC present in the matrix. During EB melting the SiC dissociated partially and interacted with the liquid Zr and resulted in different non-equilibrium phases of Zr-rich silicides during solidification.