Experimental simulation of spallation elements production in a 9Cr-1Mo martensitic steel: 3D atom probe characterisation

The irradiation damage in the target window of a demonstrator of an Accelerator Driven System (ADS) consists of atomic displacements (dpa) and spallation element production that will affect the in-service properties of the structural material of the target. The atomic displacements (about 100 dpa/year) will promote the formation of point defect clusters, dislocation loops and the precipitation of various phases that contribute to hardening and embrittlement of the structural material. As an example, the Ca and Ti production should harden the material via precipitation, in parallel to embrittlement due to P and S segregation. The purpose of this work was to simulate the spallation element loading, via ion implantation (using the IRMA implanter at CSNSM) and to study at the atomic scale, with the 3D atom probe, their evolution in the 9Cr-1Mo reference martensitic steel. In order to realize this, specific experiments, performed at 300 deg C, were carried out using low energy ions (Ca, Ti or S) implanted in the extremely small atom probe specimens (needles of 100 nanometers thickness). (authors)