Exposed to 650°C air, TP304H stainless steel with two different grain size was oxidized at this temperature. At the meantime, comparison of their oxidation was through the oxidation kinetics curves and analysis of the morphology and composition of oxide scale which conducted by SEM and X-ray. The results showed that the oxidation rate of TP304H stainless steel was slowed down by grain refinement and oxide scale of fine-grained TP304H steel was thinner than that of coarse-grained steel. The nucleation and the growth of nuclei of coarse-grained oxide scale were more rapid. In addition, the grain refinement of austenitic stainless steel accelerated the diffusivity of Cr and made for the formation of dense and continuous oxide scale, so that the oxidation of stainless steel can be effectively inhabited.

In this research, TP304 was treated by shot blasting under the pressure of 0.65MPa. The stainless steel shots used in the shot blasting experiment were in different sizes, separately with diameter 0.6mm and 1.2mm. To investigate the effect of shot blasting on the oxidation resistance behavior, steam oxidation experiments have been conducted to both original and shot blasting treating TP304s in 650°C and 25MPa. Then oxidation kinetics curve of each sample was measured by discontinuous weight method, morphology of oxide film was observed through SEM(scanning electron microscope), the component of the oxidation was measured by XRD(X-ray Diffraction), and the variation of Cr content in the oxide film was analyzed by EDS(energy-dispersive X-ray spectroscopy). According to the results, Oxidation kinetics curve in high temperature and pressure, expressed in original and shot blasting treating TP304s, both follow the principle of quasi-parabola and shot blasting can largely enhance TP304’s steam oxidation resistance in high temperature and pressure.

The feature, structure and composition of oxide films of a TP304H steel oxidized under 650°C and 25MPa water vapor for 1~50h were analyzed by SEM, EDS and XRD. The oxidizing dynamic curves were measured by discontinuous weighing method. The results indicated that the oxidation kinetics was agreement with the parabolic law. At the beginning of the oxidation, the formation of oxide was Fe2O3, while Fe3O4 and FeCr2O4 were formed with the increasing of oxidation time, without independent Cr2O3.

The corrosion failure analysis of an SA210 steel used in high pressure evaporator tube is conducted by XRD, SEM, OM. The result shows that the corrosion products in the inner wall of the steel tube is Fe3O4, mainly caused by the residual water in the evaporator tube corroding its inner wall with oxygen after the hydrostatic test of the boiler, finally leading to the corrosion leak of the tube.

Two specimens from original 10CrMo910 steel and the steel after running 147000h in high temperature were analyzed in this research by SEM, TEM, XRD and electron probe. The results show that after running 147000h in high temperature the 10CrMo910 steel has changed a lot: 1) The dislocation and subgrain boundary in bainite decreased largely while that in massive ferrite almost disappeared. 2) The strip-shape M3C carbides were nearly dissolved, the granular austenite was gradually transformed into martensite, the fine needle-shape Mo2C carbides coarsened, and granular carbides separated out in massive ferrite. 3) There were large particles of M23C6 carbides in crystal boundary between bainite and ferrite, especially in the boundary of any three phases. And creep voids appeared.