2.4. Hardness and microstructure evaluation
The surface hardness of the carburized layers was measured using
a microhardness tester fitted with a Vickers indenter under a load of
2 N. The carburized layer thickness and microstructure were examined
using an optical microscope and a scanning electron microscope
(SEM). X-ray diffraction (XRD) analysis was performed using Bruker
AXS-D8 Advance X-ray diffractometer with CuKα radiation at
1.54056 Å X-ray wavelength in order to confirm the presence of carbides
on the surfaces. The specimens were scanned from 10 to 80° 2θ
angle at a step size of 0.020 and a count time of 1 s at each step.