The influence of powder properties on the adhesion strength and microstructural evolution of cold sprayed Ti6Al4V single splats

The adhesion strength and microstructure of single splats significantly influence the properties of cold sprayed coatings. Here, we compare the adhesion strength and microstructural changes of Ti6Al4V spherical powder (SP) particles with a martensitic microstructure and irregular powder (IP) particles with an equiaxed microstructure deposited by cold spray (CS). Splat adhesion tests were performed to determine the adhesion strength and electron channelling contrast imaging was done for microstructural analysis of splat cross-sections. IP splats formed a continuous bonded interface with the substrate resulting in a greater adhesion strength when compared to SP splats. IP splat cross-sections revealed ultrafine grains (UFG) near the interface followed by a highly deformed microstructure. SP splat cross-sections also showed UFG at the interface but largely retained the initial microstructure in the top portion of the splat due to poor deformability. The irregular morphology of the IP led to more adherent deposits while the equiaxed microstructure resulted in highly deformed post spray microstructures. (C) 2019 Elsevier B.V. All rights reserved.