FORMATION OF ALUMINIUM COMPOSITE ELECTRIC ARC COATINGS WITH RED MUD ADDITION
Abstract
Abstract. It is shown that the problem of bauxite production waste disposal, namely red mud, is especially urgent for the Mykolaiv region, since the Mykolaiv Alumina Plan (MAP) is located on its territory, at the beginning of 2019 about 43.5 million tons of hazardous raw materials are stored in the sludge storage facilities. Modern methods of its processing are analyzed, consisting mainly of reductive annealing and magnetic separation with various impurities. It has been established that the direction associated with the use of red mud as a sprayed material in the application of thermal sprayed coatings is promising. With the help of metallographic analysis, the granulometric composition of the MAP red mud powder was studied. It has been established that they are characterized by a large spread of particle sizes in the range from 1 to 1000 μm. The largest number of them is less than 5 μm (35%), there is also a large amount of a fraction with a size of 10 to 50 μm (26%) and 50 to 100 μm (12%). Based on the obtained data, it was found that up to 20% of red mud can be used for thermal spraying, since the required particle size is from 40 to 80 microns. Experimental samples of composite electric-arc coatings were obtained by spraying wire from an aluminum alloy of the Al-Si system of grade ER4043 and NAP red mud powder using a modernized spraying gun EM-14M. An analysis of the microstructure of the coatings showed that they are characterized by a rather low porosity, which is about 6%; particles of red mud and Al-Si alloy are well differentiated in the structure. The phases were identified by determining their microhardness on cross sections at a load of 20 g on the indenter. It is established that the microhardness of the metal matrix is 526 MPa; red mud – 658 MPa. The planimetric method determined the amount of red mud in the coatings, which amounted to 12.2% vol. The pin method determined the bond strength of conventional from wire ER4043 (12.1 MPa) and composite ER4043 (Al-Si) – red mud (10 MPa) coatings.
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