Development and industrial tests of composite material based on TiB2 for repair of local destructions in electrolyzer bottom blocks

The paper presents the developed composition and technology for obtaining a repair mixture consisting of lumped corundum with a TiB2–C composite coating wettable with aluminum for restoration of local bottom block fractures without electrolyzer stops. The proposed technical solution made it possible to reduce bottom wear and increase aluminum electrolyzer service life by 6 months.A mixture of titanium diboride powder and a refractory powder-like binder in a ratio of 50 : 50 (wt.%) was used to obtain the repair mixture with an optimal composition. Then the lumped corundum was coated with the obtained mixture, dried at 150 °C and after that heat-treated under a carbon-bed at t= 700÷900 °C. As a result of reducing firing the TiB2–C composite material with a carbon content of 15–20 wt.% was formed on the surface of lumped corundum. A qualitative evaluation of the properties of the developed composite coating shows that the coating has a sufficiently high hardness, wear resistance and adhesion to the substrate after the heat treatment. For pilot testing, the repair mixture was covered with molten aluminum to obtain an Al–TiB2–C repair mass in the form of plates. The pilot testing of the repair mass on the 400 kA operating electrolyzer in the RUSAL-Sayanogorsk pilot shop showed that the bottom wear have slowed down 3 months after the local fractures were restored without electrolysis bath stops. This fact is evidenced by a 13 % decrease in the average depth of fractures with a stable current value of 4,7–4,8 kA/bloom after repair. Thus, the locallyused repair mass slowed that the overall wear of the cathode surface and allowed to extend the electrolyzer life.