Hot corrosion behavior of TP347HFG without and with external stresses in molten salts

The hot corrosion tests of the austenitic TP347HFG in molten sulfates with and without external stresses were conducted at 700 and 750 oC. The corroded specimens of different conditions were investigated through measurements of o xide morphology, corrosion thickness and composition. Through the analysis to the corrosion specimens, we knew that the corrosion reaction of the alloy was strongly related to the formation of an oxidation progress of metallic elements. The unstressed specimens had more complex products and thicker corrosion layers than those under 20MPa external stresses at 700 and 750 oC, which meant mo re fierce corrosion behaviors. It seemed that the applied stress led to a faster formation of a continuous, dense oxides layer that protected the inner specimens fro m further corrosion reaction. Generally, the exertion of the stresses caused many micro cracks and defects in the metal. These defects acted as faster and easier diffusion paths for the Cr atoms to diffuse to the surface, and thus, promote a faster formation of the protective Cr2O₃ oxide layer.