Cold Spray and Laser-Assisted Cold Spray of CrMnCoFeNi High Entropy Alloy Using Nitrogen as the Propelling Gas

The cold spray deposition behavior of a CrMnCoFeNi High Entropy Alloy (HEA) powder was investigated using N2 as the process gas on three different substrates of Al6061, mild steel and Hastelloy X. Well adhering and dense coatings were obtained at 950 °C and 5 MPa of propelling gas temperature and pressure, respectively. Microstructure and microhardness analyses showed significantly deformed particles in dense coatings on all three substrates, with imperfect inter-particle bonding. Laser-assisted cold spray (LACS) was used to enhance the deposition behavior of the CrMnCoFeNi powder and inter-particle bonding. Electron channeling contrast imaging analyses of coatings showed that linear structures similar to twinning are formed in the deposited particles. X-ray diffraction analysis showed that the single-phase face center cubic structure of CrMnCoFeNi powder is retained in the coatings, although peak broadening associated with grain refinement was observed. Comparison of the physical parameters (i.e., particle velocity and temperature at impact) required for deposition of CrMnCoFeNi powder with those required for conventional alloys revealed that the deposition of this HEA is significantly more challenging due to solid solution strengthening and excellent work hardenability.