Microscopic Characteristics and Mechanical Properties of Plasma Sprayed Al_2O_3 Coatings

摘要

Plasma sprayed coatings have laminated structures that consist of flat particles, voids, and particle boundaries. Such characteristic coating structures are considered to have a great influence on mechanical properties of coatings. In this research, macroscopic mechanical property differences of alumina coatings were investigated from microscopic viewpoints. The alumina coatings were prepared by atmospheric plasma spraying (APS) process and low-pressure plasma spraying (LPPS) process. Microscopic structure was investigated by microstructure observations of coatings using field emission scanning electron microscope (FE-SEM), crystalline phase distribution analysis in coating cross-section using electron backscatter diffraction (EBSD), and porosity measurement of coatings by cross-sectional image analysis. In addition, local microscopic mechanical properties were investigated by local microscopic hardness by nanoindentation method and a Young's modulus measurement. Vickers hardness test on coating cross-sections and the cavitation erosion test of coatings were carried out to investigate macroscopic mechanical properties. It was found that the microscopic characteristics of individual particles were no significant difference between each spray coating, hardness was influenced by the amounts of α phase, γ phase, and micro crystallite region, and cavitation erosion properties were influenced by the particle boundary layer.