Surface texturing has emerged in the last decade as a viable option of surface engineering resulting in significant improvement in load capacity, wear resistance, friction coefficient etc. of tribological mechanical components. Various techniques can be employed for surface texturing but Laser Surface Texturing (LST) is probably the most advanced so far. LST produces a very large number of micro-dimples on the surface and each of these micro-dimples can serve either as a micro-hydrodynamic bearing in cases of full or mixed lubrication, a micro-reservoir for lubricant in cases of starved lubrication conditions, or a micro-trap for wear debris in either lubricated or dry sliding. The present paper reviews the current effort being made world wide on surface texturing in general and on laser surface texturing in particular. It presents the state of the art in LST and the potential of this technology in various lubricated applications like mechanical seals, piston rings and thrust bearings. The paper also describes some fundamental on going research around the world with LST.

State of the art in Laser Surface Texturing

Overview no. 55 Wear-Mechanism maps

Surface texturing has emerged in the last decade as a viable option of surface engineering resulting in significant improvement in load capacity, wear resistance, friction coefficient etc. of tribological mechanical components. Various techniques can be employed for surface texturing but Laser Surface Texturing (LST) is probably the most advanced so far. LST produces a very large number of micro-dimples on the surface and each of these micro- dimples can serve either as a micro-hydrodynamic bearing in cases of full or mixed lubrication, a micro-reservoir for lubricant in cases of starved lubrication conditions, or a micro-trap for wear debris in either lubricated or dry sliding. The paper reviews the current effort being made world wide on laser surface texturing in particular. It presents the state of the art in LST and the potential of this technology in various lubricated applications like mechanical seals, piston rings, thrust bearings, magnetic recording etc. The paper also describes some fundamental on-going research around the world with LST.

State of the Art in Laser Surface Texturing

The third-body approach: A mechanical view of wear

Wear models and predictive equations: their form and content

A new theory for wear of metals is considered. The theory is based on the behavior of dislocations at the surface, sub-surface crack and void formation, and subsequent joining of cracks by shear deformation of the surface. The proposed theory predicts qualitatively that the wear particle shape is likely to be thin flake-like sheets and that the surface layer can undergo large plastic deformation. It also predicts a number of experimentally observed phenomena such as the difference in wear particle sizes and the dependence of fretting wear rate on displacement amplitude. All theoretical predictions are supported by experimental evidences. A wear equation is developed based on the proposed theory.

The delamination theory of wear

Abrasive wear mechanisms and the grit size effect

It is customary in tribological research, and especially in practice, to employ smooth surfaces, for it is generally believed that smooth surfaces should have low sliding friction. However the wear particles produced during sliding get trapped at the interfaces, and plowing by the wear particles becomes the principal mechanism of friction. Through experimental and theoretical investigations, it is shown that the plowing friction component can be substantially reduced by means of surface undulations. Steel-titanium and titanium-titanium pairs were tested to investigate the role of surface undulations in boundary lubricated sliding. Compared with the experimental results of flat titanium surfaces, friction coefficient and wear rate were considerably reduced with the undulated titanium surfaces, especially when lubricants considered ineffective for titanium were used. In addition, the effects of pad width and cavity volume fraction of the undulated surface were also investigated. A plowing model proposed for...

Nannaji Saka

Papers

The delamination theory of wear

Abrasive wear mechanisms and the grit size effect

Boundary Lubrication Studies on Undulated Titanium Surfaces

The Mechanism of Friction in Boundary Lubrication

Finite element analysis of an elastic-plastic two-layer half-space: sliding contact