PULSED-LASER DEPOSITION OF DIAMOND-LIKE CARBON WEAR PROTECTIVE COATINGS - A REVIEW

Pulsed laser deposition (PLD) is an emerging technology, which has rec ently produced diamond-like coatings (DLC) far protection against slid ing wear. In this review, the characteristics of PLD that govern the g rowth of wear resistant DLC coatings are identified, including laser p ulse energy density and wavelength, target material and substrate temp erature. Attention is given to the mechanical, tribological and wear p roperties of hydrogen-free DLC and hydrogenated H:DLC coatings produce d by laser ablation of graphite and polycarbonate targets, respectivel y. Mechanisms of friction and wear of these coatings are discussed wit h emphasis on the formation of an sp(2)-rich transfer film inside wear tracks. The DLC coatings have hardnesses of up to 70 GPa, friction co efficients about 0.1 and wear rates several orders of magnitude lower than ceramic coatings, The incorporation of DLC into advanced coating architectures to improve wear protection at high contact loads is disc ussed, including composite DLC/H:DLC coatings, functionally gradient T i-TiC-DLC coatings, and multilayer Ti-DLC nano-composites for wear pro tection at high contact loads. These advanced coatings have increased toughness and prevent DLC cracking and delamination under contact pres sures above 1 GPa. The potential of PLD DLC in wear protection applica tions is highlighted in the conclusion.