Effects of Metallographic Preparation Process on the Microstructure Evaluation of Nano-Zirconia Coating

Abstract

In order to prepare metallographic samples that accurately characterize the true state of the analyzed samples and evaluate the microstructure of the coating precisely, taking nano-zirconia coating as the research object, metallographic samples were prepared by using different inlaying methods. The influence of different grinding and polishing process parameters on the microstructure evaluation of the coatings based on orthogonal tests was investigated, and the results were verified by measuring the porosity of coatings through the nano-CT method. Results showed that the method of vacuum cold inlay could significantly reduce the phenomenon of coating particle detachment. The factors affecting the porosity of the coating in order of magnitude were the number of revolutions of the grinding disc during rough grinding, the number of fixture revolutions during rough grinding, the polishing time during rough polishing and the pressure during grinding and rough polishing. The optimized parameters for the grinding and polishing process were 15 N pressure for grinding and rough polishing, 200 r/min for the grinding disc during rough grinding, 50 r/min for the fixture during rough grinding, and 9 min for rough polishing. The porosity of the coating under this process was 4.26%, which significantly reduced the phenomenon of shedding of coating particles and allowed the preparation of metallographic samples that reflected the true microstructure of the coating, thereby achieving the goal of accurately evaluating the performance of the coating. The results obtained by the nano-CT method were consistent with the present method.

Keywords

• nano-zirconia coating; metallographic preparation; microstructure; porosity; nano-ct method