Overview
ISO 27307:2015 specifies a standardized transverse scratch test method to evaluate adhesion and cohesion of thermal sprayed ceramic coatings on substrates. The method applies to coatings from 50 μm up to and beyond 1 000 μm thickness and is also suitable for ceramic layers produced by cold spray, aerosol deposition and other spray processes. The test uses a defined diamond indenter drawn across a polished cross‑section of the coating-substrate system to distinguish cohesive failure (within the coating) from adhesive failure (at an interface).
Key Topics and Requirements
- Scope & principle
- Transverse scratch across a cross‑section; failure mode and load thresholds indicate coating strength and adhesion.
- Specimen preparation
- Recommended specimen size ~20 × 20 mm; cross‑section embedded and polished to Ra < 0.5 μm.
- Clean test area (alcohol/acetone); avoid fingerprints.
- Equipment
- Diamond indenter (Rockwell conical geometry recommended); recommended tip radius 20 μm.
- Scratch tester calibrated per ISO 20502; optional acoustic emission sensor and tangential-force monitoring supported.
- Test conditions
- Scratch length 2–3 mm; traverse speed 0.1–10 mm/min.
- Typical constant normal loads start at 3 N and proceed (examples: 3, 5, 10, 13, 15, 20 N) until adhesive failure is observed.
- At least 5 scratches per load (to account for coating heterogeneity).
- Environmental control recommended: 22 °C ± 2 °C, 50 % ± 5 % RH.
- Evaluation & reporting
- Classify failures as no crack, cohesive crack, or adhesive crack; a mode is considered dominant if >30% of observations.
- Report must include environmental conditions, coating/substrate materials and thickness, coating process, indenter tip radius, traverse speed, test loads, and percentage of each failure mode.
Applications - Who Uses ISO 27307:2015
- Coating manufacturers and process engineers validating thermal barrier, wear‑resistant or corrosion‑protective ceramic coatings.
- Quality control and R&D labs assessing adhesion/cohesion of plasma spray, cold spray, aerosol-deposited ceramics.
- Material scientists comparing coating-substrate systems, or verifying process changes and design choices.
- Procurement/specification writers who need a repeatable method to rank coating performance.
Related Standards
- ISO 20502 - referenced for calibration and scratch test procedures for fine/advanced ceramic coatings.
ISO 27307:2015 provides a reproducible, cross‑sectional transverse scratch test protocol for quantifying and reporting adhesion and cohesion of thick and thin ceramic spray coatings - essential for reliable coating qualification, failure analysis, and process optimization.
Open preview (PDF)Thermal spraying — Evaluation of adhesion/cohesion of thermal sprayed ceramic coatings by transverse scratch testing
