Microstructural and Micromechanical Analysis of Cold Sprayed CrMnCoFeNi High Entropy Cantor Alloy Coatings

CrMnCoFeNi High Entropy Alloy (or Cantor alloy) powder was cold sprayed using nitrogen process gas. A thick and dense coating was successfully obtained on a mild steel substrate with a process gas temperature and pressure of 950 °C and 4.9 MPa, respectively. Due to its unique properties and complex composition, rising interest in the CrMnCoFeNi Cantor High Entropy Alloy and its use in thermal spray coatings has been noted since its creation in 2004. In this work, an in-depth analysis of the cold sprayed CrMnCoFeNi coating was done to provide insight on the mechanical properties and features present in the different microstructural regions of the coating. X-ray diffraction analysis of the coating showed that the single-phase FCC structure of the CrMnCoFeNi feedstock powder was retained after cold spraying. Significant deformation of the powder particles was observed. Nanocrystalline regions were observed at the splat interfaces which exhibited a high nano-hardness (~ 5.4 GPa) due to deformation-induced grain refining. The splat centers did not undergo grain refining, but still exhibited a higher nano-hardness (~ 4.5 GPa) than the feedstock powder (~ 3.3 GPa) due to the presence of deformation-induced dislocations revealed with scanning transmission electron microscopy. Furthermore, electron channeling contrast imaging and scanning transmission electron microscopy revealed the presence of linear deformation-induced dislocations in the coating microstructure, indicating that mechanical twinning could be a deformation mechanism occurring during cold spray of Cantor alloy powder.