Oxide cracking behaviour of Cu-added 18%Cr-8%Ni austenitic alloy after steam oxidation. (June 2020) - Yan, Jingbo
Highlights: The Cu segregates at Fe3 O4 /FeCr2 O4 and scale/matrix interface during oxidation. Oxide inward growth facilitates the super saturate of Cu at alloy subsurface. Extensive Cu-riched particle precipitated at alloy subsurface during oxidation. Dislocation shears the Cu-riched phase during the deformation of alloy subsurface. Higher energy stores at subsurface retard the oxide cracking of Cu adopted alloy. Abstract: In this work, the oxidation behaviour of Cu-added 18 %Cr-8%Ni alloy was investigated. A duplex scale with outer Fe3 O4 and inner FeCr2 O4 layers was formed on the alloy surface. Due to its low oxygen affinity, Cu was ejected and segregated around the Fe3 O4 /FeCr2 O4 interface and the scale/matrix interface during oxidation. Moreover, the supersaturation of Cu at the subsurface facilitated the extensive precipitation of Cu rich particles. As the dislocation shearing of these particles requires higher stress, the major fraction of strain energy was consumed at the subsurface. Thus, crack nucleation and propagation in the oxide scale on Cu-added alloy were suppressed.