Influence of Ag content on mechanical and tribological behavior of DLC coatings

Abstract

Ag-DLC coatings with Ag contents ranging from 1.3 at.% to 13.1 at.% were deposited by DC magnetron sputtering. The coatings were characterized with respect to their structure (by means of XRD and Raman Spectroscopy), mechanical and tribological properties (by scratch test, nanoindentation, residual stress measurements and pin-on-disk test). The incorporation of 13.1 at.% Ag resulted in the formation of Ag grains with 2-3 nm which promoted the increase of graphite like bonds organized in rings. Regarding the mechanical properties, no variations were found for films with Ag contents lower than 13 at.%; a reduction of both hardness and compressive residual stress were then observed for higher values. Pin-on-disk tests were performed at two different contact pressures (690 MPa and 1180 MPa) in dry sliding conditions against a zirconia counterpart. For the lower contact pressure the variations in the wear rate are well correlated with the coatings structure and mechanical properties, while for higher contact pressure the presence of Ag is relevant, Ag-DLC coatings showing higher wear rate than DLC one. SEM analysis revealed the formation of Ag aggregates on the wear track and adhesion of silver to the counterpart.

A Microstructural and Wear Resistance Study of Stainless Steel-Ag Coatings Produced through Magnetron Sputtering

“…This behaviour can be attributed to a good solid lubricant, Ag, which allows lubricating the wear tracks of the coating and friction pairs, so the sliding between the two surfaces tends to be facilitated, lowering the COF of the film. The quality of silver as a solid lubricant depends on its ability to segregate and hold during a certain number of cycles on the surface, so if the segregation of silver is low, the wear rate will not be affected but if the segregation is high, the wear rate is influenced by the time it takes for the silver to run out, since once exhausted the solid lubrication ability of the film is reduced and the surface has an unstable porous structure, causing failure and an increase in the wear rate [15,16]. Figure 8 shows the results of the wear rate in the produced coatings.…”

“…The deposition of coatings containing silver has been a subject of interest in applications where materials with good tribological and antibacterial properties are required. Evidence has been shown of a tendency to increase the durability of the different types of compounds that contain silver, because in many cases properties such as the wear resistance and the coefficient of friction are improved, which can be attributed to the possible action of silver as a solid lubricant on the surface of the coatings, thus reducing wear [15][16][17].…”

Electrochemical response of ZrCN-Ag-a(C,N) coatings in simulated body fluids

“…Low wear resistance in titanium alloys [1], toxicity in CrCo alloys [2] and limited localized corrosion resistance in 316 L stainless steel [3], the most used materials for medical applications [4,5], showed the need of producing a multifunctional material that can enhance the mechanical, tribological, chemical and biological properties. These characteristics have been modified by applying chemical inert coatings with low-reactive ceramic material, such as diamond-like-carbon materials [6,7], nitrides [8][9][10], carbides [11], carbonitrides [12], or oxides [9,13]; carbonitrides present the best compromise between the mechanical, triboglogical and corrosion resistance performance. Moreover, in order to potentiate the materials biocompatibility, antimicrobial agents, such as silver, can be included [14][15][16][17][18][19].…”

Spectroellipsometric characterization and modeling of plasmonic diamond-like carbon nanocomposite films with embedded Ag nanoparticles

“…have been used to modify structures and properties of the films [5][6][7][8]. Among them, the Ag-incorporated diamond-like carbon films have increasingly gained attention because of wide applications in optical device applications [9], biomedical implants due to surface anti-bacterial properties [10], solar energy [11], electronic devices [12], for catalysis effect [13], and tribological applications [14,15]. When atomic concentration of the group IB metal (silver, copper, or gold) in the diamond-like carbon film is more than several atomic percents, due to silver (copper, gold) segregation, silver (copper, gold) nanoclusters embedded in the diamond-like carbon matrix were detected [5,8,9].…”