observed confronting the values measured at the top (carburized)
with those measured on the sample bottom (untreated). Changing
the CH4 content from 0.25% to 1.00% resulted in a slight increase of
the top surface hardness from 589 to 638 HV0.3. On the other hand,
an average value of 375 HV0.3 was verified at the bottom surface,
which is a result of the tempering effect produced due to heating of
the sample, as the treatment is carried out