Investigation of Corrosion Behavior of Stainless Steels As a Function of Composition, Grain Size and Austenite to Martensite Phase Ratio

Abstract

It is well established that the severe plastic deformation of metastable austenitic stainless steels causes martensitic transformation and the annealing of deformation induced martensitic phase induces reverse transformation from martensite to austenite the ratio of which has been found to be a factor of alloy compositions and annealing / sintering temperatures. In this study, nanocrystalline austenitic stainless steels of different compositions will be synthesized from elemental powders by using high energy mechanical milling. As-milled powders will be cold-consolidated and sintered at elevated temperatures up to 1100 ºC in order to facilitate a better densification for the subsequent experiments and alter the microstructure i.e., grain size and austenite to martensite phase ratio. Microstructural evolutions as a function of alloy compositions and sintering temperatures will be investigated using focused ion beam, transmission electron microscopy and in-situ / ex-situ x-ray diffraction techniques to determine the grain sizes and phases upon milling and sintering. The corrosion behavior of austenitic stainless steels will be determined using immersion and electrochemical tests at various temperatures. The electrochemical corrosion tests will be conducted using a flat corrosion test and a potentiostat. The relative importance of compositions, grain sizes and austenite to martensite phase ratios will be discussed with respect to corrosion behavior of the studied stainless steels.