Study On Fabrication And Oxidation Behavior Of 12Cr-ODS Fe-based Superalloys

In this thesis, the development of Fe–based superalloys was reviewed. Based on the above work, Fe-12Cr-2.5W-0.4Ti-0.3Y₂O₃ superalloy powders were prepared by milling. Then the Fe-based superalloys were prepared by annealing, compacting and sintering. The effects of pressing pressure, sintering temperature and addition of Si on microstructure and properties at room temperature of this superalloy and its oxidation behavior were studied, by means of relative density test, hardness test, tensile test, oxidation test, X–ray diffraction analysis (XRD), optical microscopy (OM), scanning electron microscopy (SEM) and energy depressive analysis (EDS).The compact's density of alloy increased with the increase of pressing pressure, and the curves were liner to parabola. Simultaneity, the porosity of the alloys became smaller. The performance of Fe–based alloy could be optimized by increasing pressing pressure and sintering temperature. The relative density and hardness of the sample pressed under 760MPa and sintered at 1420℃were respectively 86.4% and 145HV.The oxidation degree increased with the elevation of temperature and the extension of time whereas the speed of the mass gain change decreased with the extension of time. And the curves of gained mass were liner to parabola. It can be concluded that oxidation dynamic equations are respectively (?W)4.31=3.99t and (?W)1.97=7.367t from the curves of Fe-based alloys under 650℃and 850℃conditions. When oxidized at 650℃, the oxide layer was compact with comparatively preferable ability to resist from oxidation, while the layer of 850℃was with phenomenon of desquamation and discontinuous of its inside layer which had lost its ability of protection.Relative density, tensile strength and ability of oxidation resistance of Fe-12Cr-2.5W- 0.4Ti-0.3Y₂O₃ could be obviously enhanced by addition Si. The relative density and hardness of alloy without Si were only 85.9% and 300.96 MPa, while they were up to 97.26% and 692.7MPa after adding Si. The oxide layer of alloy with 0.2% Si was only 40μm and compact even after oxidation at 850℃for 100h. It can be concluded that oxidation dynamic equations of alloy with 0.2%Si is (?W)1.3=0.0367t from the oxidation curves at 850℃.