Large-area high-rate pulsed laser deposition of smooth TiC xN 1− x coatings at room temperature—mechanical and tribological properties

Abstract

Titanium carbonitride (TiC x N 1− x ) hard coatings possess excellent tribological behavior in metal punching and forming as well as high biocompatibility. Because almost all PVD and CVD coating techniques for TiC x N 1− x coatings require substrate temperatures higher than 150–200 °C for reaching sufficient adhesion strength to the substrate surface, there is high demand in the development of large-area and high-rate low-temperature vacuum deposition processes. In the present work, this call was fulfilled by the application of the room temperature pulsed laser deposition (PLD) for TiC x N 1− x coating with various carbon ( x) and nitrogen contents. A pulsed Nd:YAG laser (wavelength: 1064 nm) was used for the vaporization of pure titanium targets in low-pressure N 2/C 2H 2 atmospheres. The highly ionized metal vapor was deposited onto polished substrates (molybdenum, AISI D2 steel), forming a nearly particulate-free, very smooth and dense film structures, which can be hardly reached by using other PVD techniques. The variation of the gas flow during deposition causes a change of the chemical composition and the microstructure of the nearly particulate-free coatings, and, consequently, of the mechanical and tribological properties. The solid solution hardening of the fcc TiN lattice by low contents of carbon increases the hardness and elastic modulus, while higher carbon contents decrease this effect. Furthermore, the maximum in hardness and elastic modulus correspond with the minima in the friction coefficients (∼0.2) and wear rates of both the coated disc and the counterparts (AISI 52100 (DIN 100Cr6) ball-bearing steel balls).