Sliding Wear Resistance of Borided AISI 4140 Steel

In this study, adhesion properties and wear behavior of both AISI 4140 and borided AISI 4140 steels were obtained. The monophasic iron boride layer (Fe₂B = ~ 22 µm) was obtained on the surface of the AISI 4140 steel preheated at 773 K for 30 min to prevent thermal shock; afterward, the samples were submitted to 1173 K for an exposure time of 30 min. The layer obtained was characterized by Berkovich nanoindentation, optical microscopy, and x-ray diffraction. Dry sliding wear tests were performed using two constant loads (2 and 20 N) at considering relative sliding distances (144 and 288 m), according to the ASTM G133 standard procedure. Wear mechanisms such as material agglomeration, plastic deformation, grooving, plowing, and smearing were identified as the principal failure mechanisms by Scanning Electron Microscopy on the worn track. The results showed that the presence of the single-phase Fe₂B layer on the surface of the AISI 4140 steel increased the wear resistance around ~ 20 times compared to the material without boron for a 288 m of sliding distance and 20 N of load.