Embrittlement susceptibility induced by impurities segregation to grain boundaries in martensitic steels candidates to be used in ADS

Grain boundary microchemical characterization, by Auger electron spectroscopy, has been performed in the martensitic steel EM-10 doped with relevant spallation elements that are expected to be produced at the spallation target window in future Accelerator Driven Systems (ADS). A heat treatment of step-cooling was performed in all doped materials to accelerate impurity segregation. The results indicate that step-cooling promotes chromium and molybdenum enrichment at the grain boundaries in the four materials studied. Step-cooling promotes phosphorus segregation to grain boundaries in the reference material, in the material doped with titanium, and in the material doped with titanium, phosphorus and sulphur. Step-cooling also promotes titanium enrichment in the materials doped with this element. A relation among chromium, molybdenum and phosphorus has been observed in the alloy doped with titanium, phosphorus and sulphur suggesting co-segregation of these elements to grain boundaries or segregation of phosphorus at the interface of the matrix and the carbides rich in chromium and molybdenum.