Submicron coatings for micro-tribological applications

Abstract

The miniaturisation of mechanical components and machines enables innovative future products. However, for the improvement of functionality, reliability and lifetime of those micro systems, micro tribological coatings with thicknesses in the sub-micron range are needed. To cover these needs, we investigated different submicron coatings with the aim to develop wear and friction optimized thin films for this application. The basis of this work has been the state of the art know how of well established macroscopic coatings which in general are in a thickness range of a few micrometers. It turned out, that particularly the surface topography and the substrate material influence the properties of very thin films. For investigations with single asperity contact, the coefficient of friction (COF) was reduced by lowering the tip radius and the hardness of the substrate material. In contrast, for larger contact radii (pin-on-disc), an increase of the COF with decreasing substrate Young's modulus was found. With respect to wear, it turned out that the wear depth increased dramatically with increasing initial surface roughness (R(ind a))

Tribological improvement of moving microparts by application of thin films and micropatterning

“…The NiFe films were prepared by electroplating. The preparation parameters of the films are described in detail elsewhere [6,[29][30][31][32].…”

“…Typical thicknesses are in the range of a few nanometres for applications in hard discs [10,11] as well as a few microns for macroscopic applications [12]. Due to the small forces, but high local pressures in MEMS components important R&D work is focused on wear-resistant surfaces with minimized friction and low stick-slip behaviour [13][14][15][16]. Due to the modified geometry and contact situation of microsystems several aspects of microtribology must be considered [10,[17][18][19].…”

Effect of physical vapor deposition metallic thin films on micro injection molded weld line mechanical properties

“…While regarding to micro injection molded polymeric parts, the metallic coating layers/thin films with special electrical, magnetic and mechanical properties always are adhered on the micro polymer parts' surface, satisfying with the MEMS's multi-functional demands by chemical vapor deposition (CVD), physical vapor deposition (PVD) and electroforming etc. (Bedenbecker et al 2008;Bandorf et al 2004;Pichonat and Gauthier-Manuel 2007;Quandt and Holleck 1995;Rusu et al 2004). However, in the mean time when the parts' electrical and magnetic features are changed, their mechanical properties are modified as well due to the varying of stress distribution from these external coating layers.…”

Tribological Characterization of Several Silicon-Based Materials Under Ionic-Liquids Lubrication

“…Proper lubrication schemes are imperatively needed to provide long contact endurance and acceptable reliability [7,8]. Different solid tribological coatings (e.g., high quality amorphous carbon) and thin films (e.g., organic self-assembled monolayers (SAMs)) have been extensively developed [9][10][11][12][13][14][15]. Nevertheless, these lubricant films still have shortcomings in spite of considerable progresses made, for instance, adherence, fluctuation in coefficient of friction (COF), finite wear life, tribo-reactivity, poor thermal conductivity and complex deposition procedures, etc., are the great challenges that the solid coating should face [16]; SAMs organic films may degrade by aging due to their chemistry changes in humid or oxidizing environments, volatility in vacuum environments, and sensitivity to temperature fluctuations [7,17].…”