ISO 19207:2016

Overview

ISO 19207:2016 - Thermal spraying - Classification method of adhesive strength by indentation defines a practical indentation-based method to classify the adhesive strength of thermal spray coatings at room temperature. Using a Vickers hardness testing machine, the standard quantifies an adhesion index (AI) from the maximum indentation force that does not produce a visible interfacial crack. The method is applicable to relatively dense metal, ceramic and cermet coatings and intended for comparison within a coating system.

Key topics and requirements

• Test principle: A pyramidal Vickers (or optional special conical) indenter is pressed at the coating/substrate interface. An interfacial crack forms when the applied force exceeds adhesive strength; the critical indentation force is the maximum force without visible cracking and defines the adhesion index.
• Applicable coatings: Dense metal, ceramic and cermet thermal spray coatings. Not recommended for very thin coatings, very porous coatings, or systems where cohesion < adhesion.
• Porosity guidance: Recommended for coatings with porosity less than approximately 15%.
• Indenter and apparatus:
  • Standard Vickers indenter per ISO 6507-2.
  • If no crack appears with Vickers due to very high adhesion, a special conical diamond indenter (point angle 70°, point radius 0.05 mm) may be used.
  • Indentation machines must meet ISO 6507 requirements.
• Sample and preparation:
  • Substrate thickness recommended ≥ 5 mm.
  • Coating thickness: at least 2× the half-diagonal of the impression for high-stiffness coatings; ≈5× for low-stiffness coatings.
  • Sample width ≥ 5 mm, length > 20 mm; polished, damage-free surface; samples embedded in resin.
• Measurements:
  • Optical microscope calibration required; resolution at least 10 μm (recommended magnification 200×) to measure impression diagonals and crack lengths.
• Test conditions: Room temperature, normal laboratory air, rigid support and perpendicular test surface.
• Reporting: Test validity, test force series, impression/crack measurements, adhesion index and test-piece details.

Applications and users

ISO 19207 is used for:

• Quality assurance and production control of thermal spray coatings
• Selection and evaluation of spray materials/processes
• R&D and failure analysis for coating adhesion performance Typical users: thermal spray laboratories, coating manufacturers, materials engineers, QA engineers, research institutions and spec writers drafting coating acceptance criteria.

Related standards

• ISO 6507-1 / ISO 6507-2 - Vickers hardness test (method and machine verification)
• ISO 14917 - Thermal spraying terminology/classification
• ISO 14923 - Characterization and testing of thermally sprayed coatings

Keywords: ISO 19207, thermal spraying, adhesion index, Vickers indentation, coating adhesion test, cermet, ceramic coatings, thermal spray coatings.