  In this paper synchrotron microtomography on Plasma Sprayed Tungsten (PS-W)
is presented and discussed. PS-W is a challenging material for microtomography
since it exhibits a random porous network at different length-scales (from
nanometers to micrometers) and is hardly penetrable by X-rays. Furthermore,
inner porosity causes strong internal scattering. The key challenges were,
firstly, to optimize the beam parameters considering the inherent trade-off
between photon energy (penetration depth) and spatial resolution and, secondly,
to develop effective signal filtering algorithms. Despite the limited
signal-to-noise ratio detected, large volumes of PS-W could be reconstructed
with good image quality and micrometric resolution (voxel size = 1.4 {\mu}m).
As an important result, we report excellent image quality and higher
penetration depth by applying the same setup on a ferrous microstructure,
namely a 10%W/Steel MMC used as interlayer between PS-W and a
ferritic/martensitic steel substrate. The paper reports a detailed 3D
morphological analysis of all inclusion types in PS-W and W/Steel, which led to
disclosure of a complex connected porous network in both media. The analysis is
presented in terms of multiphase volume fraction, ratio of percolation and 3D
shape descriptors. 3D percolation patterns are analyzed in detail and
sensitivity towards segmentation threshold for the noise-affected PS-W region
is discussed. Remarkably, percolation of the porous phase was found throughout
the entire coating thickness of PS-W. In W-Steel MMC percolation was found in
the perpendicular plane and interpreted as onset of delamination caused by
thermomechanical stress.
