Unraveling of the statistical correlation between porosity, permeability and diffusivity of cold-sprayed Ti6Al4V

Abstract

The fluid transport properties of cold-sprayed deposits have hitherto barely been addressed compared to the mechanical properties. This study used a small cold-sprayed Ti6Al4V “tsunami” deposit with a unique porous structure, which was consolidated by helium carrier gas on the mild steel substrate holder due to instantaneous fluctuations of nozzle traverse speed. The porosity was measured to be 15 % by densitometer, 35.5–54 % by optical microscope and 1–34 % by XCT experiments with selected ROIs. The XCT tensor simulated porosity, mean absolute permeability and mean effective diffusivity were able to be correlated statistically with power functions. The transport properties posted a positive-linear relationship at porosities ranging from ~2.5–30 %, where the ranges of permeability and diffusivity were from ~1.0E+2 to 5.0E+4 mD and from ~1.0E-9 to 1.0E-7 m2/s, respectively. It was also noted that the changing formation factor and the cementation factor in the computing algorithms led to unaligned diffusivity prediction at critical porosity, which was below 13 % in this study. The range of fluid transport properties can thereby be potentially predicted on-site with a statistical correlation approach based on porosity. This paper aims to provide insights into developing comprehensible process and inspection guidelines for cold-spraying components for fluid transport and fluid-tight applications.