Diamond-like carbon coatings designed for high contact stress applications

Research output: Conference Papers (RGC: 31A, 31B, 32, 33)31A_Invited conference paper (refereed items)Invitedpeer-review

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Detail(s)

Original languageEnglish
Publication statusPublished - Jul 2018

Conference

Title9th International Conference on Technological Advances of Thin Films and Surface Coatings (ThinFilms2018)
LocationVenus Royal Hotel, Shenzhen
PlaceChina
CityShenzhen
Period17 - 20 July 2018

Abstract

As a tribological coating, diamond-like carbon (DLC) is well known for its combination of low friction and high wear resistance. These exceptional tribological abilities explain the increasing production of DLC coatings and the global share of DLC coatings keeps increasing from $0.8 billion in 2005 to $1.7 billion in 2015. DLC has found its way into a large variety of applications such as, automobile parts, magnetic hard disks, medical implants, razor blades, and microelectromechanical systems (MEMS). The harsh service condition in heavily loaded automobile parts, such as gudgeon pins, cam followers, gears and bearings, demands high load capacity from the DLC coatings. However, the DLC often fails where high contact stresses are required due to poor adhesion, high residual stresses and poor toughness of the DLC coating. Typically, under lower contact stresses (< 2 GPa) the specific wear rate of hydrogen-free carbon coatings (a-C) is in the range of 10-9-10-7mm3/Nm, but most of coatings fail rapidly at higher contact stresses. From existing literature, the studies on DLC films working under high stresses (> 2 GPa) are rare and a few groups can only push the wear rate into the range of ~10-7mm3/Nm which is at least one order of magnitude higher than that of coatings under low stresses. Thus, it is an ongoing challenge for the coating community to design DLC films working under high contact stresses with low wear rate. To tackle the issue, the approaches are discussed in this paper: (i) multilayer DLC coatings with alternate hard phase and soft phase, (ii) isolated carbon particles embedded amorphous DLC coating matrix. In summary, the wear rate of the tuned multilayer coating (~ 2.0ξ0-8 mm3/Nm) is one order of magnitude lower than that of DLC coatings found from the current literature (~10-7mm3/Nm). Furthermore, the load bearing capacity of the multilayer coating can be as high as 4.0 GPa, which almost doubles the values found from current DLC coatings. As for the isolated carbon particles embedded DLC, it has achieved a wear rate of ~6×10-9 mm3/Nm when tested at the contact stress of 2.8GPa. At higher contact stress of ~3.2GPa, all the baseline DLCs failed quickly while all nanoparticles embedded DLC coatings survived at least 2,000 cycles at 300rpm velocity. The best results were obtained for the sample which was embedded with 1-layer of carbon nanoparticles and it survived 6,000 cycles. Thus, this work suggests that the hardness and toughness can be increased around 10% to 20% and at same time the wear rate can be reduced by a factor of 3 after embedding least amount of isolated carbon nanoparticles in amorphous DLC coatings.

Research Area(s)

  • Diamond like carbon, Residual stress, TOUGHNESS, Multilayer coating, magnetron sputtering, High contact stress, Carbon particles, multilayer

Citation Format(s)

Diamond-like carbon coatings designed for high contact stress applications. / Lin, Yanyan; Zia, Abdul Wasy; Zhou, Zhifeng; Li, Kwok Yan.

2018. 9th International Conference on Technological Advances of Thin Films and Surface Coatings (ThinFilms2018), Shenzhen, China.

Research output: Conference Papers (RGC: 31A, 31B, 32, 33)31A_Invited conference paper (refereed items)Invitedpeer-review