Plasma Treatment Effect on Structure and Properties of Protective Coatings for Chamotte Refractories

The relevance of the work is driven by the need to improve the operational durability of linings in thermal generating sets in metallurgy, power engineering, and chemical industry, where traditional protection (concrete spraying, kiln lining coating) do not provide sufficient durability due to low adhesion and differences in thermal expansion coefficients. Purpose: The aim of the work is to develop compositions and process conditions for the plasma-assisted formation of protective coatings on the surface of chamotte refractories in order to improve their thermal resistance and adhesion strength. Methodology/approach: High-refractory materials – bakor (ZrO 2 –Al 2 O 3 –SiO 2 system), corundum (α-Al 2 O 3 ), and chamotte powder – were used as modifying components. Based on the analysis of phase diagrams and melting curves obtained for Al 2 O 3 –SiO 2 and Al 2 O 3 –SiO 2 –ZrO 2 systems, a three-component composition containing 50 wt.% chamotte, 25 wt.% bakor, and 25 wt.% corundum was selected. This composition provided the formation of the gradual liquidphase and a stable glass-crystalline layer. The powder mixtures were milled to a target fraction of 80–100 μm, mixed with a sodium silicate binder (liquid glass) to obtain a paste, applied to the refractory surface in an ~1 mm layer, dried, and then treated with a concentrated low-temperature plasma flow. The evolution of the phase composition of coatings was studied by the X-ray diffraction analysis during thermal cycling (10 cycles of heating to 1200 °C with air cooling). Adhesion strength was tested before and after thermal cycling Practical implications: The quality of the initial fire brick is a critical factor of the successful plasma spraying. The results can be used in the development of industrial technologies for strengthening linings of thermal generating sets.