Pulsed laser deposition of diamond-like carbon wear protective coatings: a review

Abstract

Pulsed laser deposition (PLD) is an emerging technology, which has recently produced diamond-like coatings (DLC) for protection against sliding wear. In this review, the characteristics of PLD that govern the growth of wear resistant DLC coatings are identified, including laser pulse energy density and wavelength, target material and substrate temperature. Attention is given to the mechanical, tribological and wear properties of hydrogen-free DLC and hydrogenated H:DLC coatings produced by laser ablation of graphite and polycarbonate targets, respectively. Mechanisms of friction and wear of these coatings are discussed with 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 coefficients 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 discussed, including composite DLC/H:DLC coatings, functionally gradient Ti-TiC-DLC coatings, and multilayer Ti-DLC nano-composites for wear protection at high contact loads. These advanced coatings have increased toughness and prevent DLC cracking and delamination under contact pressures above 1 GPa. The potential of PLD DLC in wear protection applications is highlighted in the conclusion.