The Raman investigation of the samples showed the existence
of a carbon layer consisting of fine-crystalline graphite. In the
brighter areas of the boost step only sample the size of graphite
crystallites was 1.0e7.0 nm, and in the darker areas of
7.0e20.0 nm. The diffusion step led to a decrease in the size of
the crystallites. The graphite that occurred in the areas with
homogenous brightness had crystallites of size 1.0e2.0 nm,
whereas, in the areas where the gray shade was not homogenous,
the crystallites were 4.0 nm. This indicates that carbon settles in
the form of fine-crystalline graphite during the boost steps. This
graphite is subjected to further refinement in the diffusion steps.
Taking into consideration the results of papers [5e7] it can be
assumed that, during LPC of charges consisting of steel parts, an
active carbon layer settles in the form of fine-crystalline graphite
and hydrocarbon radicals on the surface of the parts. The layer
mediates in transporting carbon from the gas atmosphere to the
austenite and provides an additional source of carbon in the
diffusion steps.