Effect of Alternating Magnetic Field Treatment on the Friction/Wear Resistance of 20Cr2Ni4A Under Lubricated Conditions

High-strength nickel–chromium steel (20Cr2Ni4A) is typically used in bearing applications. Alternating magnetic field treatment, which is based on the use of a magnetiser, and which is fast and cost-effective in comparison to conventional processes, was applied to the material to improve its wear resistance. The results of pin-on-disc wear testing using a AISI 52100 alloy counter pin revealed a decrease in the specific wear rate of the treated samples by 58% and a reduction in the value of the coefficient of friction by 28%. X-ray diffraction analysis showed a small increase in the amount of martensite and higher surface compressive residual stresses by 28% leading to improved hardness. The observed changes were not induced thermally. The volume expansion by the formation of martensite was achieved at near room temperature and led to a further increase in compressive residual stresses. The significance of this study is that the improvement in the properties was achieved at a current density value that was two orders of magnitude higher than the threshold for phase transformation and dislocation movement. The reasons for the effect of the alternating magnetic field treatment on the friction and wear properties are discussed in terms of the contribution of the magnetic field to the austenite-to-martensite phase transformation and the interaction between the magnetic domain walls and dislocations.