X-ray photoelectron spectroscopy (XPS) was used to study the tribo-films formed due to thephase transformations occurred at the cutting tool/chip interface. The XPS equipment consisted ofa Physical Electronics (PHI) Quantera II spectrometer with a hemispherical energy analyzer, an Alanode source for X-ray generation, and a quartz crystal monochromatic for focusing the generatedX-rays. The samples were sputter-cleaned before collecting the data. The beam for data collectingwas 100 micrometers, and all spectra were obtained at a 45◦take off-angle. The neutralization of all samples was ensured.