Assessment of elastic properties of coatings by three-point bending and nanoindentation

The elastic properties of a thermally sprayed coating were determined by a three-point bending (3PB) test and nanoindentation, but different results were obtained by the two methods. The microstructure revealed by scanning electron microscopy shows the existence of pores which decrease the overall resistance of the coating to elastic deformation. Therefore, the overall mechanical properties determined by the 3PB test are influenced by pores. On the other hand, the mechanical properties of the materials determined by nanoindentation are rarely influenced by pores, as indentations are normally made far away from pores. As a result, the Young’s modulus determined by the 3PB test is lower than that determined by nanoindentation. Selection of the method to determine the Young’s modulus of the coating must be carried out with careful consideration.