Friction in vacuum and under different gaseous environment of magnetized sliding ferromagnetic contact

Abstract

The direct metal/metal sliding contact causes a severe wear with a high friction coefficient and an important wear rate. Applying magnetic field into the rotating sliding steel Fe360 B/steel Fe360 B modifies the friction and the wear behavior of the contact. The experimental tests were conducted in three different environments such as: ambient air, pure oxygen at 105 Pa and high vacuum at 5.10−5 Pa. In ambient air and without magnetic field, the metal/metal contact is ductile. When a magnetic field is applied, the formation of oxide layer evolves progressively with the number of sliding cycles. This contact has a low friction and mild wear. Under oxygen, the oxide film appears in wear track with and without applied magnetic field. The wear rate under oxygen is lower than that in ambient air with a ratio roughly equals to 10. In oxygen, the average value of friction coefficient µ decreases from µ = 0.41 to µ = 0.30. In vacuum, the increase of surface hardness causes a transfer of particles from the disc towards the pin. This transfer modifies the morphology of the wear track, increases the surfaces roughness and leads to a strong adhesive wear. The different analysis obtained with: microscopy, micro-harness, wear losses, EDX and friction evolution explains the effect of applied magnetic field on the friction behavior of Fe360 B steel.