CoatingIQ
Coating reference

PVD coating · reference

Diamond-Like Carbon

DLC·a-C:H / ta-C (amorphous carbon, sp2/sp3 mix)·Black

Amorphous carbon coating family; hydrogenated a-C:H (softer, lower temp) through hydrogen-free tetrahedral ta-C (harder, higher temp), often with Cr/Me adhesion or doping layers

Properties (cited ranges)

Hardness
1,000–9,000HV
Max service temp
300–450C
Friction vs steelsteel (100Cr6-class / coated steel ball), dry unless noted; lubricated runs lower
0.06–0.25coefficient of friction (mu)
Thickness
0.5–8um
Deposition temp
160–250C

Dot = source confidence (high medium low). Ranges, not single numbers — real coatings vary by process and supplier.

Typically chosen for

  • Engine and powertrain components (piston pins, valve lifters, injectors, gears) for low-friction wear reduction
  • Cutting/forming tools and dies for non-ferrous and abrasive work, anti-galling and anti-adhesion
  • Precision sliding components, bearings, pump and valve parts needing dry/low-lubrication running
  • ta-C grades where maximum hardness and higher temperature resistance are required

Diamond-Like Carbon (DLC)

DLC is not one coating but a family of amorphous carbon films, defined by the mix of sp2 (graphite-like) and sp3 (diamond-like) bonds and by whether hydrogen is present. The soft, low-temperature end is hydrogenated a-C:H; the hard, hotter-running end is hydrogen-free tetrahedral ta-C. It exists to do one thing the nitrides cannot: run with very low friction against metal, dry or near-dry, without galling or building up edge.

What the numbers say

  • Hardness ~1,000–9,000 HV (typical a-C:H band ≈2,500). This is a family envelope, not a single measured value: Me-DLC sits near 1,000–2,000 HV, common a-C:H around 2,000–3,000, and ta-C climbs to 5,000–9,000. Pick by grade, not by the headline span. [calico-dlc, ionbond-tb42, richter-titankote, ionbond-tb48]
  • Max service ~300–450°C (typical ≈350), oxidation/graphitization-limited. a-C:H tops out near 300–350°C; ta-C buys roughly another 50–100°C (400–450°C). Above its grade limit the film degrades. [ionbond-tb42, richter-titankote, calico-dlc, ionbond-tb48]
  • Coefficient of friction ~0.06–0.25 against steel, dry (typical ≈0.1), measured against a steel counterface (100Cr6-class / coated steel ball, ball-on-disc per ASTM G99). Lubricated it runs below 0.10. This is DLC's whole reason for being — far slicker than TiN (~0.4). [ionbond-tb42, ionbond-tb48, richter-titankote, calico-dlc]
  • Thickness 0.5–8 µm (typical ≈2.5): ta-C is laid down thin because sp3 compressive stress limits build, while a-C:H multilayers go thicker. Deposited 160–250°C — low enough for hardened, tempered steels. [ionbond-tb48, richter-titankote, ionbond-tb42, calico-dlc]

Where it fits

DLC earns its place wherever friction and adhesion — not raw heat — are the problem. That means engine and powertrain parts (piston pins, lifters, injectors), precision sliding and bearing components running dry or lightly lubricated, and forming/cutting tooling for non-ferrous and abrasive work where galling and built-up edge would otherwise kill the surface. Reach for ta-C when you need the most hardness and the extra temperature headroom; reach for a-C:H or doped grades when you need thicker, lower-stress films at lower deposition temperatures.

Vendor-neutral note: these are general process properties for understanding tradeoffs — not a specification for your application. Real selection needs a coating house with your substrate, geometry, and duty data.

Sources (5) · medium confidence · not yet handbook-verified