CVD Coating for Extrusion Screws and Barrels
CVD coating (Chemical Vapor Deposition) is a chemical vapor-phase deposition process in which volatile compounds such as TiCl₄ and acetylene are decomposed under vacuum and deposited as a hard, amorphous layer on the surface of the screw. The result is coatings such as TiN, TiC, and DLC (Diamond-Like Carbon) — diamond-like carbon layers with outstanding tribological properties.
With a coating thickness of only 2–4 µm and a hardness of approx. 1,800 HV, the metallic amorphous coating offers a unique combination of wear resistance, low friction, and chemical resistance — without altering the dimensional accuracy of the screw.
Key Properties at a Glance
- Coating thickness of 2–4 µm — no change to screw geometry
- Amorphous structure with very high density and low surface roughness
- Hardness approx. 1,800 HV
- Extremely low coefficient of friction
- Excellent adhesion to the base material
- Low electrical conductivity
- Also applicable as an internal coating up to max. 10 D — ideal for barrels and tubes
- Coating temperature below 200 °C — suitable even for temperature-sensitive components
Advantages Compared to Conventional Surface Treatments
- Significantly reduced build-up and adhesion tendency
- Extended service life compared to nitrided or hard chrome-plated surfaces
- No post-polishing required
- Environmentally friendly — dry process without heavy metals such as chromium(VI)
Applications in Plastics and Rubber Processing
- PVC extrusion — protection against corrosive chlorine compounds and material build-up
- PE/PP extrusion — minimization of deposits and improved flow behavior
- PUR processing — outstanding non-stick properties for reactive melts
- PMMA, POM, ABS — protection against sticking and corrosion attack
- Glass fiber reinforced plastics — increased service life with abrasive fillers
- Rubber and elastomers — ideal for NBR, EPDM, and natural rubber compounds with high adhesion tendency