The Structure and Porosity of Plasma Coatings

Porous coatings are actively used in engineering practice. The porous coating determines the reliability of the operation of the intraosseous implant and the heat transfer process when the aggregate state of the refrigerant is changed. The choice of method for quantitative analysis of porosity is determined by the structure of the coating. In this study, plasma coatings sprayed from powders were analyzed. A porosity of 10.3% inside the alumina coating was analyzed by mercury porosimetry. The main volume of the porosity of the coating is formed by pores ranging in size from 0.13 to 0.36 μm; their share in the total volume is 68.29%. The remaining volume is distributed in sizes of 0.04–0.12 mm, 0.58–4.66 mm, and 5.66–18.2 mm. Microtomography makes it possible to get a more complete general idea of the macro- and microstructure of coatings, establishing the mechanisms of its formation, and to obtain data on the real shape of the pores. A quantitative description of the visible pores of three-dimensional capillary-porous 3CaO⋅Al2O3 coatings in the form of ridges and depressions was determined by raster image analysis using special STIMAN programs. The porosity of this coating is 39.7% of the distribution over four pore groups: 0.74–3.56, 4.34–11.57, 14.08–55.65, 67.73–267.71 mm.