Mechanism of transfer film formation during repeat pass sliding of ceramic materials

Abstract

The formation of transfer film and the consequent effects on the friction and wear behavior of ceramic materisIs during repeat sliding contact were studied. This was done using four structuraI ceramics, namely silicon nitride, silicon carbide, ahunina and zirconia, with a cylinder-on-flat test configuration. The transfer film consists of reattached fme wear debris particles, the film, whenever formed, is strongIy attached, enough to resist being wiped off by the slider. Cahxdations suggest that the Sne particles are attached primariIy by van der Wsals forces and to a lesser extent by electrostatic attractive forces. As a consequence, the formation of transfer ti leads to a decrease in the wear rate because of the 'protecting' role of the SIm. The presence of the ti at the contact interface also results in high friction. The presence of a liquid environment and/or surface active species reduces the particle adhesive forces and hence can inhibit the formation of a transfer f%n.

Effect of Tribofilm Formation on the Dry Sliding Friction and Wear Properties of Magnetron Sputtered TiAlCrYN Coatings

“…In addition, it has been reported that oxide wear debris generated in a humid environment contains some level of hydration and the hydroxide component of the wear debris exhibits lower friction than the pure oxide alone [24,25]. In the sliding wear of TiAlCrYN, coatings being tested at RH = 33% showed lower wear coefficients than those tested at RH = 23% (Table 2).…”

“…The TiAlCrYN coatings exhibited wear coefficients in *10 -16 m 3 N -1 m -1 scale at relative humidity of 30%-33%, whereas a small decrease of the humidity to 23%-25%, led to considerably higher wear coefficients in the scale of *10 -15 m 3 N -1 m -1 . It was reported in literature that water molecules can be absorbed on the wear debris and tribofilm to result in lower severity of adhesive interaction within the sliding contact zone [24,25].…”

Effects of Temperature on Tribological Properties of Al2O3-TiO2 Coating

“…It was thought that the cracks would propagate along areas of weakness in the underlying material under cyclic stress due to the strong adhesion between the transferred surface layer and the underlying material, i.e., a fatigue process was involved 19 . Since the intersplat bonding is weak in the plasma-sprayed ceramic coating 20,21 , the delamination was along the splat boundary, and accordingly, a large crater was produced. It was inferred that the wear rate of the coating would increase if the sliding distance was increased.…”

Hierarchical adaptive nanostructured PVD coatings for extreme tribological applications: the quest for nonequilibrium states and emergent behavior

“…Here dS i /dt is entropy production as a result of the distribution of heat and other flows within a body; dS e /dt-flow of entropy due to external impact, which could change due to the transition of heat from a hotter friction surface into a colder body (the cutting tool) and which results in an increase of entropy; dS m /dt-change of entropy due to the formation of chemical compounds on the tool surface due to the entropy of the matter from the contacting frictional body (in our case, it is mostly due to cutting tool-chip interactions with further formation of seizure zones or buildups [165,176,177]); dS f /dt-change of entropy due to tribofilm formation; dS w /dt-change of entropy due to wear process (the '−' sign is used in the equation because the wear products leave the frictional body with their own entropies). The change of entropy, dS f /dt, could be negative, if nonequilibrium processes are taking place on the surface and entropy of a frictional body is reduced, or positive, if the equilibrium processes are going along [174].…”