Quantifying Dislocation Density and Recrystallization Kinetics in Laser-Heated Cold Sprayed SS304L

The dislocation density and recrystallization kinetics in laser-heated cold sprayed SS304L are investigated for the first time via a combination of neutron diffraction, the convolutional multiple whole profile (CMWP) method, differential scanning calorimetry (DSC), and electron diffraction. These results are then coupled with thermal simulations to provide a more complete picture of the rapid recrystallization process in laser-heated cold sprayed SS304L. It was found that the cold sprayed process resulted in a uniform dislocation density throughout the material, and laser heating showed rapid recrystallization in the samples, resulting in reduced dislocation density. Furthermore, it was found that at lower heating rates, the cold sprayed material exhibited distinct recovery and recrystallization temperatures. At high heating rates, the more rapid kinetics of recrystallization at the prior particle interface regions become more pronounced than those at the prior particle interior, leading to the necklacing of recrystallized grain at the prior particle interface around the prior particle interior at 750 °C. Comparison of these results with thermal simulations and measured in situ dislocation density as a function of temperature shows that the resulting microstructure and degree of recrystallization can be approximated by the maximum temperature reached at any location. This allows the optimization of coating properties and tool path geometry using thermal simulations.