| Title |
Pesearch Paper / Materials Processing : A study on the Fabrication of Ni - Cr / Steel Graded Boundary Material by Electron Beam |
| Authors |
김재현(Jae Hyun Kim),김도훈(To Hoon Kim) |
| ISSN |
1738-8228(ISSN), 2288-8241(eISSN) |
| Abstract |
For a development purpose of thick metal/metal graded-boundary materials, a preliminary research on the fabrication of graded-boundary Ni-Cr/steel material was carried out by an electron beam and its mechanical properties and thermal characteristics were investigated. In order to produce a compositionally graded boundary region between substrate steel and added Ni-Cr alloy, a series of surface alloying treatments was performed with an electron beam. Ni-Cr sheet was placed on a low carbon steel plate(0.18%C), and then an electron beam was irradiated on the surface to produce a homogeneous alloyed layer. On this first surface-alloyed layer another Ni-Cr sheet was placed and then the electron beam was irradiated again to produce second surface-alloyed layer. Sequential repetitions of electron beam surface alloying treatment 4 times resulted in a graded-boundary region with the thickness of about 2.2 ㎜. Simultaneous concentration gradients of different kinds of alloying elements(Ni and Cr) showed from 28%Ni, 29%Cr and 43%Fe on surface region to 0%Ni 0%Cr and 99%Fe in substrate region. A thermal conductivity gradient resulted in graded-region and its value changed from 0.028 ㎈/㎝ s℃ in surface region to 0.1 ㎈/㎝ s℃ in substrate region. Microstructural observation showed that any visible root porosities and solidification shrinkage cracks were not formed in graded region between alloyed layers and substrate steel during rapid cooling. |