Design of low-friction PVD coating systems with enhanced running-in performance — carbon overcoats on TaC/aC coatings

Abstract

The widespread use of low friction PVD coatings on machine elements is limited by the high costs associated with fulfilling the demands on the surface quality of both the supporting substrate and the counter surface. In this work, an attempt is made at lowering these demands, by adding a sacrificial carbon overcoat to a TaC/aC low friction coating. Both coatings were deposited by planar magnetron DC sputtering, as separate steps in a single PVD-process.Coatings were deposited on substrates of two different surface roughnesses, in order to test the ability of this coating system to function on rougher substrates. Reciprocating ball on disc tests were performed, using balls with two different surface roughnesses. The worn surfaces were investigated using 3-D profilometry and SEM. The ability of the different overcoats to initially reduce the roughness of both the coated surface and the counter surface and to produce stable, low-friction conditions was examined for the different initial roughnesses. The implications for design of efficient run-in coatings for various systems are discussed.

Fabrication and characterization of DLC coated microdimples on hip prosthesis heads

“…However, the obtained roughness of the samples is still acceptable considering the surface roughness reported in other studies investigated on artificial hip joints . Figure (c,d) shows the images of a‐C:H (light dark) and Ta‐C (dark)—the SEM images shows the morphologies of both form of DLC that are similar to the DLC images published in other studies . However, the ratio of Sp 3 and Sp 2 bonding could not be measured in this study.…”

Creation of anti-frost micro-plastic texture surfaces enhancing thermal conductivity by carbon black containing in polyvinyl chloride

“…However, the PVC has low thermal conductivity, therefore, we should improve thermal conductivity of PVC with making a shape mimicking lotus leaf surface without high cost. The authors were facing the problem of being able to treat the particle-like carbon formed in the chamber during the deposition of carbon-based hard thin coatings only as waste during their researches (Tokoroyama et al, 2012;Nyberg et al, 2013;Tokoroyama et al, 2016;Lee et al, 2018;Taib et al, 2018;Aboua et al, 2018;Hashizume et al, 2021;Tokoroyama et al, 2022). While this carbon is considered waste, it is speculated to have a high thermal conductivity due to its high graphite content.…”

Effect of phosphonate additives with hydroxy groups on tribological properties of ta-C coatings under boundary lubrication

“…However, it is difficult to achieve both low friction and wear resistance using multiple additives, because additives developed for steel materials have been reported to promote wear on the surface of DLC coatings [1][2][3][4][5][6][7][8][9][10], and when multiple additives are used simultaneously, the target additive is not adsorbed on the surface [5,11,12]. The search for the optimal additive is ongoing because DLC is roughly devided tetrahedral amorphous carbon (ta-C) [13][14][15][16][17][18][19][20], hydrogenated amorphous carbon (a-C:H) [21][22][23][24][25][26], amorhous carbon (a-C) and other doped one [27][28][29][30][31][32][33][34]. Thus, conventional additives prepared for steel-based materials have not been sufficiently effective for DLC coatings, which have become popular in recent years.…”