Powder Solid-State Additive Manufacturing

Production of free-standing cladding tubes with cold spray deposition

SEM images of (a) 14YWT ODS steel powder and (b) cross-section of ODS steel deposit produced by the cold spray process
Subsequent surface polishing of the deposit and dissolution of the aluminum-alloy mandrel leaves behind a free-standing ODS steel cladding tube.






Advanced reactor concepts will require materials for in-core structural applications that resist radiation damage (several hundred dpa) and retain creep strength at high temperatures. Ferritic oxide dispersion strengthened (ODS) steels provide these advantages through their fine dispersion of oxide nanoparticles within a ferritic steel matrix. The distribution and number density of these oxide nanoparticles are crucial for exhibiting these superior properties. The current manufacturing process includes ball milling a gas atomized powder with subsequent powder extrusion and annealing processes. These multiple extrusion steps are time consuming and not scalable to larger-scale manufacturing. Cold spray technology has the potential to eliminate these multiple extrusion steps providing a much more cost-effective and economically viable manufacturing route.

We have successfully manufactured ODS steel cladding tubes using the cold spray process using  14YWT steel gas atomized feedstock powder provided by Oak Ridge National Laboratory. The powder is sprayed onto a rotating aluminum-alloy mandrel with the cold spray nozzle traversing in the axial direction. The inner aluminum-alloy mandrel is subsequently dissolved in a 20% NaOH solution to leave a free-standing ODS steel tube.

ODS tube ground to 800-grit surface finish

We have also coated the highly oxidation-resistant FeCrAl (Fe-20Cr-5Al) alloy by the cold spray process onto an ODS steel tube. Oxidation experiments of this multilayered deposits as well as other multilayer coatings will be performed and developed in the coming months.

Future Work

  • Vacuum heat treatment experiments to remove porosity
  • Further optimization by altering feedstock powder composition
  • Mechanical testing to compare cold spray ODS steel cladding to conventional ODS cladding
  • APT characterization of oxide nanoparticles
  • High temperature oxidation testing of FeCrAl coatings deposited on ODS

See our publication in Nuclear Engineering and Technology

STEM bright-field image of (a) 1000 °C annealed ODS steel tube showing re-precipitation of oxide nanoparticles and (b) SEM image of multilayer coating of FeCrAl sprayed on ODS with arrows indicating FeCrAl/ODS interface.