  The effect of non-planar substrate surface on homogeneity and quality of cold
sprayed (CS) deposits was studied by scanning acoustic microscopy (SAM). Fe
coatings were cold sprayed onto Al substrates containing artificially
introduced grooves of square- and trapezoid-shaped geometries, with flat or
cylindrical bottoms. The Al substrates were either wrought or cold sprayed, to
comprehend their prospective influence on the Fe coatings build-up. SAM was
then used to assess morphological properties of the materials from the
cross-view and top-view directions. The microstructure below the surface of the
studied samples was visualized by measuring the amplitudes of the reflection
echoes and the velocity of the ultrasonic waves. The SAM analysis revealed that
the regions of coating imperfections around the grooves are larger than what is
suggested by standard scanning electron microscopy (SEM) observations.
Furthermore, we found that the seemingly non-influenced coating regions that
appear perfectly homogeneous and dense in SEM do, in fact, possess
heterogeneous microstructure associated with the individual CS nozzle passes.
