Isothermal and Cyclic Aging of 310S Austenitic Stainless Steel

Unusual damage and high creep strain rates have been observed on components made of 310S stainless steel subjected to thermal cycles between room temperature and 1143 K (870 °C). Microstructural characterization of such components after service evidenced high contents in sigma phase which formed first from δ-ferrite and then from γ-austenite. To get some insight into this microstructural evolution, isothermal and cyclic aging of 310S stainless steel has been studied experimentally and discussed on the basis of numerical simulations. The higher contents of sigma phase observed after cyclic agings than after isothermal treatments are clearly associated with nucleation triggered by thermal cycling

External α -Al2O3 Scale on Ni-Base alloy 602 CA – Part II: Microstructural Evolution

The growth of protective α-Al2O3 scales on the NiCrAl-base alloy 602 CA at 1100 °C and 1200 °C was promoted by multi-step oxidation treatments. Different microstructural changes were observed during high temperature exposures in the pre-oxidised specimens as compared to the bare specimens. A coupled thermodynamic-kinetic model was employed to describe the influence of pre-oxidation on the microstructural evolution in the alloy. The model was able to correctly predict the mechanisms of the dissolution and re-precipitation of the carbides in the pre-oxidised and bare specimens