In the primary and secondary circuits of CANDU nuclear power plant, austenitic and martensitic steels are used as structural materials. In such environmental conditions these materials exposed to water results in corrosion. The improvement of the surfaces corrosion resistance is very important from nuclear safety point of view. Thermo electrochemical treatments of bath carburizing and nitriding represent a good choice for these improvements. Because the mechanical and anticorrosive properties are related to the microstructure of surfaces it is important to make good microstructures characterization of the protective surface layer.

The austenitic and martensitic steels samples thermo electrochemical treated were analyzed by X-ray diffraction (XRD) techniques. The acquisitions of diffraction patterns were performed in symmetrical Bragg-Brentano focusing geometry and asymmetrical geometry using a conventional powder diffractometer. The depth profile phases identification of modified surfaces is obtained in the asymmetrical arrangement. The line profile analyses were applied in order to determine the mean crystallites size and the micro-strains of the surface layer.

By low angle XRD we found that Fe₃O₄ appear as external layer both on austenitic and martensitic steel. On to the martensitic steel the surface layer contains also CrC and CrN for carburizing respectively nitriding treatment. The results obtaining by low angle XRD were confirmed by SEM-EDX measurements. The surface layer microstructures do not differ too much for austenitic and martensitic steel after carburizind treatments. By nitriding treatments, the microstructures of martensitic steel layer is different of austenitic steel surface layer.

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