The boost step was carried out at a temperature of 950 C and
using a pressure fluctuation of 6e7 hPa. The charge consisted of the
ballast, comprising low-carbon steel sheets with a specified surface
area, and samples of C15 steel. The samples were of 20 10 mmdia.
with a polished flat face surface. The carburizing parameters were
a low pressure (4 Pa), heating up to 950 C at a speed of 10 C/min,
heating under low pressure conditions for 30 min at a temperature
of 950 C, performing a specified number of boost and diffusion
steps at this temperature and then cooling down to the room
temperature in a nitrogen stream under a pressure of 0.5 MPa. The
study included two processes: the 506 process 3n_15d_2 n (3 min
of boostþ15 min of diffusionþ2 min of boost); the 505 process e
3n_15d_2n_1d (as process 506 þ1 min of diffusion). The carburized
face surface of the samples was subsequently observed in the
polarized light of the optical microscope and the electron microscope
(JEOL 5600JV). Moreover, Raman scattering of the light was
investigated with a LabRAM HR 800 spectrometer (HORIBA Jobin
Yvon) with different laser excitations: 633, 514, and 488 nm. The
spectra were recorded from different places on the sample. Using
the optical microscope connected to the spectrometer it was
possible to choose a region on the sample.