Carburization of the HK40 alloy: study of the microstructure

S. SIMONETTI; G. BRIZUELA; C. LANZ

Montreal

Conferencia; Materials Science & Technology 2013- MS&T13; 2013

MS&T

An analysis of a HK-40 structure changes after service is also presented by using optical and electron microscopy techniques to better elucidate the mechanism of stress corrosion cracking of iron-nickel-chromium alloys exposed to high temperature. Complementary theoretical calculations, electronic structure and the chemical bonding, are also presented. The experiments in real used samples show the formation of carbides and the loss in mechanical properties that can be explained on the bases metal-C bonds formation at expenses of metal-metal bonds. The atomic orbital occupations of the metallic bonds close to the C atom are affected. The mainly changes are presented in Ni 4s, Fe 4p and Cr 4p orbitals. The strengths of the Fe-Ni, Cr-Ni, Ni-Ni and Fe-Cr bonds nearest neighbors to C atom are the most affected. The metallic bond weakening is mainly a consequence of the new C-Ni, C-Fe and C-Cr interactions.