Mechanical and structural characterisation of bioactive coatings

摘要

Hydroxyapatite powders were made by reacting orthophosphoric acid with calcium hydroxide and dense bioactive coatings were subsequently produced by the plasma spraying technique. Three types of flame spheroidised hydroxyapatite monolayer coatings and two types of functionally graded coatings were manufactured. Precursor powders and bioactive coatings were characterised using various techniques. Micro-indentation was employed to assess mechanical properties of coatings. The crack propagation behaviour was also investigated. It was found that anisotropy of mechanical properties of as-sprayed coatings existed, which was related to the lamellar structure produced by the plasma spray technology. Average microhardness values of monolayer coatings decreased as the indentation load increased. The relationship between indentation load and indent diagonal observed Meyer's law. It was revealed that microhardness was affected by characteristics of precursor powders used for plasma spraying. The indentation fracture toughness of as-sprayed coatings was in general agreement with data found in the literature.