The properties of microarc oxidation coatings installed on AlSi10Mg specimens produced by selective laser melting

Abstract

This paper examines the properties of coatings produced by microarc oxidation (MAO) on AlSi10Mg alloy specimens, which were obtained by selective laser melting. Two different electrolytes were used to install the coatings: silicate and silicate-phosphate. Modes were used that are recommended for the microarc oxidation of high-silicon aluminium casting alloys. As a result, double-layer coatings of different thicknesses were produced in relatively close timeframes of the MAO process. The thickness, roughness and wear spots were analyzed with the help of a laser interference microscope; the hardness was measured on a microhardness tester; the morphology and the elemental composition of the MAO coatings were analyzed by means of scanning electron microscopy (SEM); an X-ray diffractometer was used for phase analysis. The measurements showed that the coatings produced in the silicate-phosphate electrolyte have higher microhardness, corrosion resistance and specific electrical strength. Based on the results of friction tests and having analyzed the Ffr – Dr hysteresis loops obtained for reciprocating wear of the specimens, with the friction force Ffr and the travel D being simultaneously measured, the authors established that the wear resistance of the coatings produced in silicate-phosphate electrolyte is ~1.4 times higher than in the case of silicate electrolyte. The conducted study confirmed the efficiency of using silicate-phosphate electrolyte for producing high-quality protective coatings, which applies to almost all parameters. The paper shows that MAO coatings installed on AlSi10Mg alloy specimens produced by selective laser melting offer high performance. Thus, they can be recommended for pilot production of spacecraft components.This research was carried out as part of an assignment of the Ministry of Education and Science of Russia, Subject No.: FSFF-2020-0014.