Remarkable friction stabilization of AISI 52100 steel by plasma nitriding under lubrication of alkyl naphthalene

AISI 52100 steel was treated by means of plasma nitriding and exhibited remarkable friction stabilization when sliding against AISI 52100 steel under lubrication conditions with alkyl naphthalene, compared with heat quenched and untreated samples. In the presence of lubricant additives, ZnDDP and PN (amine salt of alkoxyl phosphate), the system displayed excellent friction steady-state and low friction coefficient between 0.10 and 0.11 at different frequencies at 300 N. The phase composition of the nitrided layer was examined by X-ray diffraction (XRD) and the worn surfaces were analyzed by scanning electron microscope and X-ray photoelectron spectroscopy. It indicated that the stability was mostly attributed to the change in the microstructure and phase composition of the nitrided steel surfaces and tribochemical reactions between lubrication additives and sliding pairs.