Characterization of microstructure and corrosion properties of cold worked Alloy 800

X-ray diffraction studies indicated that cold worked (∼50%) Alloy 800 was austenitic and transmission electron microscopy revealed the presence of a small volume fraction of hexagonal ε-martensite along with deformation bands, high dislocation density and primary TiN particle with a few dislocations within it. The passivity of cold worked alloy was very stable in H2SO4 solution but unstable in HCl solution at room temperature. The exposure of cold worked alloy in 673 K steam (initial pH of water was 10.1) for a period of 264 h showed almost nil corrosion rate. Scanning electron microscopy revealed a number of small oxide particles on the surface exposed in steam indicating initiation of oxide formation. Energy dispersive X-ray analyses of the surface containing small oxide particles indicated that the surface composition was similar to bulk composition of the alloy. X-ray photoelectron spectroscopy revealed that the alloy surface exposed in steam contained mixed oxides of iron and chromium as well as elemental form of iron, nickel and chromium.