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.

Friction Evolution of Graphite Bearing Impregnated with Polymer Subjected to Vibration Fretting at High Temperature

“…During contact, sites are formed in notch positions on monoatomic height steps. These highly energetic sites, separated by low-energy surfaces, create adhesive bonds during contact, leading to severe friction and wear [3,[8][9][10][11][12][13][14][15][16][17][18][19][20][21]. In the presence of water vapor, these sites become saturated, reducing their reactivity.…”

Fretting study of an impregnated graphite bearing/nitrided stainless steel in a dry contact submitted to severe thermal-vibratory loading

“…In industrial applications, graphite is more used as a solid lubricant when it is impossible to use a fluid lubricant and graphite has good tribological qualities due to its particular structure. 6,15–24 However, graphite remains less adaptable in high temperature applications since it is highly sensitive to the humidity and to the surface desorption phenomenon. 5,23–26…”

“…In industrial applications, graphite is more used as a solid lubricant when it is impossible to use a fluid lubricant and graphite has good tribological qualities due to its particular structure. 6,[15][16][17][18][19][20][21][22][23][24] However, graphite remains less adaptable in high temperature applications since it is highly sensitive to the humidity and to the surface desorption phenomenon. 5,[23][24][25][26] Moreover, in the industrial world of graphite, it is known that the addition of some metallic elements that have a low melting temperature (tin, antimony, bismuth, copper or silver, etc…) improve its tribologicl behavior.…”