Beyond Thin Film Limits—Superhard and Hydrogen‐Free Amorphous Carbon Coatings With Over 100 µm Thickness

Hard protective coatings substantially improve properties of tribological loaded components but require mechanical support from the substrate. The application limit is reached when high local stress from penetrating hard particles causes plastic deformation of the underlying substrate and subsequent coating breakage. Thicker coatings can mitigate this effect, but thin film technologies are typically restricted by high residual stress and limited adhesion strength of the substrate‐coating interface. This work reports a superhard tetrahedral amorphous carbon (ta‐C) coating with a thickness of over 100 µm. This was achieved by developing a deposition procedure enabling low residual compressive stress (1–2 GPa) and sufficient adhesion. Mechanical and structural characterization demonstrates a homogeneous, amorphous carbon layer with more than 50% sp 3 content, without visible interfacial delamination under the investigated indentation and scratch conditions. Load bearing tests with a Rockwell indenter at 100 N normal load show plastic substrate flow and complete coating failure for a 1.5 µm thin coating, but only negligible deformation of the otherwise intact coating with 100 µm thickness. Calculations of the stress distribution show that the maximum load is transferred into the thick coating, protecting the substrate from plastic flow and enabling self‐supporting coatings for extreme loads.