The Influence of the Substrate on the Deposition of Cold-Sprayed Titanium: An Experimental and Numerical Study

The deposition of cold-sprayed titanium on various substrates is studied in this work. A rather coarse powder of titanium (-70 + 45 mu m) was sprayed under uniform spraying conditions using a cold spray system onto five different substrates: two aluminum-based alloys (AISI 1050-H16 and AISI 2017-T4), copper, stainless steel AISI 304L, and Ti-6Al-4V. All the spraying experiments were carried out using alternatively nitrogen (N-2) or helium (He) as the process gas. Thick coatings were formed on the various substrates, with the exception of the AISI 2017 substrate. When N-2 was used as the process gas, only a few particles remained adhering to the AISI 2017. The thick pre-existing superficial oxide layer on AISI 2017, which was detected by Electron MicroProbe Analysis (EPMA), appeared to prevent adhesion of cold-sprayed titanium particles. The interaction of the sprayed particles with the various substrates was also studied by means of numerical simulations to better understand the adhesion mechanisms. The microstructure and the characteristics of the coatings were investigated. Deposition efficiency and coating density were found both to be strongly improved by spraying helium as the process gas.