Statistically Guided Development of Laser-Assisted Cold Spray for Microstructural Control of Ti-6Al-4V

Abstract

Laser-assisted cold spray (LACS) was used to deposit Ti-6Al-4V powders onto Ti-6Al-4V substrates using nitrogen as a carrier gas. An L25 orthogonal array was created with three parameters independent of particle velocity considered thus to be the independent thermal parameters (ITPs) of LACS: powder feed rate, raster speed, and laser power. A signal-to-noise analysis of the influence of the ITPs on porosity, microhardness, and expected thickness was performed revealing that optimum parameter selection is highly dependent on the targeted property, with the ITPs having the largest influence on porosity. Additional bulk trials (>2.5 mm thick) were deposited using parameters of interest from the orthogonal study. These scaled trials demonstrate that it is possible to produce deposits of Ti-6Al-4V via LACS using nitrogen as a carrier gas with porosity less than 1 pct, which is comparable with values described in literature for more expensive helium-based cold spray of Ti-6Al-4V. Additionally, variation of the ITPs indicates that secondary phases and morphologies can be produced and controlled through the thermomechanical treatment caused in situ to LACS.