An improved Vickers indentation fracture toughness model to assess the quality of thermally sprayed coatings

• Empirical indentation models tend to be based on an idealised cracking pattern.
• Surface cracking during Vickers indentation is indicative of the volumetric damage.
• A new Vickers indentation fracture model (edge crack) has been proposed.
• New model is a way forward in determining the indentation fracture toughness.
• Finite element simulation of the indentation was conducted to study stress fields.

This study presents an improved approach to the quality assessment of thermally sprayed coatings. Measurements were carried out on five different coatings. Since it is the overall extent of surface cracking during Vickers indentation that is indicative of the volumetric damage, the surface crack length was measured, including the radial cracks, edge cracks, and other cracks around the indentation. It is concluded that the proposed model provides a way forward for determining the fracture toughness (K1c) of brittle materials where no radial cracks are developed. An elastic–plastic finite element simulation of the Vickers indentation test was conducted to locate the stress fields.