Tribological Properties of Diamond-Like Carbon Films

Diamond-like carbon (DLC) films are amorphous carbon coatings characterised by a mixture of sp³‐bonded (diamond‐like) and sp²‐bonded (graphite‐like) carbon. Their unique hybrid structure confers exceptional hardness, low friction coefficients and high wear resistance, making them ideal for applications ranging from precision bearings and cutting tools to biomedical implants and space mechanisms. Tribological performance derives from a balance between bulk properties (density, hydrogen content, internal stress) and surface phenomena (formation of protective tribolayers, chemical passivation and environmental interactions). Under sliding contact, DLC surfaces often undergo rehybridisation, tribo‐film formation and chemical reactions with lubricants or ambient species, which can lead to superlow friction regimes and enhanced durability. The global significance of DLC tribology spans automotive fuel efficiency, reduction of industrial energy losses, extended lifetime of medical implants and reliable operation of mechanisms in extreme environments such as nuclear reactors and outer space.

Research from Nature Portfolio

Recent studies have elucidated the atomic‐scale mechanisms underpinning superlubricity in hydrogenated and doped DLC films. Advanced microscopy and spectroscopy reveal that dry sliding of hydrogenated amorphous carbon promotes the formation of nanoscale tribolayers through selective rehybridisation pathways, yielding an ultra-low friction state that depends sensitively on contact mechanics and counterpart materials. Complementary work on tetrahedral amorphous carbon has demonstrated that organic friction modifiers with reactive centres can bridge bearing surfaces and undergo mechanically induced fragmentation, releasing passivating functional groups that form continuous lubrication films and deliver near-zero wear. In a related development, investigations under oleic acid lubrication have shown that tribochemical reactions convert the DLC surface into ultra-thin graphene-like oxide sheets, which act as solid lubricants and sustain friction coefficients below 0.01 in moving assemblies.

Tribological Properties of Diamond-Like Carbon Films publication trend

The graph below shows the total number of articles in tribological properties of diamond-like carbon films across all publications each year (not limited to Nature Index journals).

Technical terms

Diamond‐like carbon (DLC): Amorphous carbon film combining sp³ and sp² bonding, notable for hardness and low friction.

sp³/sp² hybridisation: Types of carbon bonding; sp³ yields tetrahedral networks (hard), sp² yields planar networks (softer).

Tribolayer: A thin film formed at the sliding interface that protects surfaces and modulates friction.

Superlubricity: A sliding regime characterised by ultra-low friction coefficients, often <0.01.

Fretting fatigue: Combined wear and fatigue damage occurring under oscillatory contact with small amplitude.

Mechano-chemical tribochemistry: Chemical reactions induced by mechanical action at sliding interfaces, altering surface chemistry and lubrication.

References

1. Properties and Classification of Diamond-Like Carbon Films. Materials (2021).
2. Achieving superlubricity in DLC films by controlling bulk, surface, and tribochemistry. Friction (2014).
3. Diamond-Like Carbon (DLC) Coatings: Classification, Properties, and Applications. Applied Sciences (2021).
4. Evolution of tribo-induced interfacial nanostructures governing superlubricity in a-C:H and a-C:H:Si films. Nature Communications (2017).
5. Mechano-chemical decomposition of organic friction modifiers with multiple reactive centres induces superlubricity of ta-C. Nature Communications (2019).
6. Diamond-like carbon coating under oleic acid lubrication: Evidence for graphene oxide formation in superlow friction. Scientific Reports (2017).
7. Multi-functional bioactive silver- and copper-doped diamond-like carbon coatings for medical implants. Acta Biomaterialia (2023).
8. The effect of various treatment parameters in duplex plasma nitrided and diamond-like carbon coating on high-cycle fatigue and fretting fatigue lifetimes of piston pin 16MnCr5 steel. Applied Surface Science Advances (2024).
9. Insights into irradiation-affected structural evolution and mechanical behavior of amorphous carbon. Acta Materialia (2024).