Development and optimization of diffusion bonding process for ODS alloys at the example of PM2000

Future nuclear power plants are designed for increased efficiency, for the appropriate structural materials high radiation resistance and increased thermal stability are required. A candidate material class are the oxide particle dispersion strengthened chromium steels (ODS steels). ODS steels can withstand operating temperature above 550 C without swelling. The oxide particles have sizes of a few to some tens of nanometers with homogenous distribution in the steel matrix. Conventional welding methods are not applicable to ODS steels since the particles agglomerate in the liquid phase and decrease strength and toughness of the material. A promising joining technique is the solid state diffusion welding, deformation and diffusion processes form a new grain structure at the interface. TEM investigations show no particle distribution changes up to 1200 C. The development and the optimization of the diffusion welding process for the ODS steel PM2000 is performed supported by simulation. The calculated welding parameters (welding temperature, welding pressure, holding time, surface roughness) are validated by mechanical and microstructure tests of the welded samples. The experimental results are the basis for the next iterative step of model improvement.