EFFECT OF SURFACE CONDITION ON THE OXIDATION BEHAVIOR OF HK40 ALLOY UNDER LOW OXYGEN PARTIAL PRESSURE

摘要

The oxidation behavior of HK40 alloy (an oil cracking tube material) with different surface finishes (electrolytic polished, mechanical polished, grinded and sandblasted) was studied at 950°C, in H_2-H_2O atmosphere. The oxidation kinetics, morphology, chemical composition, phase composition of oxide scale were examined by Thermo-gravimetric Analysis (TGA), Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS) and X-ray diffraction (XRD). Results demonstrated that, the oxide scale formed on the samples with different surface conditions were all composed of Cr_2O_3 and MnCr_2O_4. The oxidation kinetics of four samples followed cubic law and oxidation rate increased with the increasing of surface deformation. Oxide ridges formed on the electrolytic polished sample, with the increasing of the surface deformation, the ridges gradually disappeared.