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http://dx.doi.org/10.12656/jksht.2012.25.2.074

Effect of χ Phase on the Impact Toughness of 25Cr-7Ni-4Mo Super Duplex Stainless Steel  

Kang, C.Y. (Dept. of Metallurgical Engineering, Pukyong National University)
Han, H.S. (Busan Campus of Korea Polytechnic VII)
Lee, S.H. (Dong Busan Campus of Korea Polytechnic VII)
Han, T.S. (Korea Lift College)
Publication Information
Journal of the Korean Society for Heat Treatment / v.25, no.2, 2012 , pp. 74-79 More about this Journal
Abstract
This study has been carried out to investigate the precipitation behavior of ${\chi}$ phase and effect of ${\chi}$ phase precipitation on the impact toughness of 25%Cr-7%Ni-4%Mo super duplex stainless steel. It was proved that the ${\chi}$ phase was a intermetallic compound, which represented the higher chromium and molybdenum concentration than the matrix phases, and also showed the higher molybdenum concentration than the ${\sigma}$ phase. The ${\chi}$ phase was precipitated at the interface between ferrite and austenite or inside the ferrite matrix in the early stage of aging. The number of ${\chi}$ phase precipitates increased with increasing aging time, however, after showing the maximum value, the number was decreased due to the gradual transformation of ${\chi}$ phase into ${\sigma}$-phase. Aging ferrite phase was decomposed by the $r^2$ phase and ${\sigma}$-phase. Impact toughness rapidly decreased with time in the initial stage of aging at ${\chi}$ phase start to precipitate. Thus, the impact toughness was greatly influence for the precipitation of ${\chi}$ phase.
Keywords
${\chi}$ phase; Super duplex stainless steel; Impact toughness; Aging time; Intermetallic compound;
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