Flame-sprayed rice husk ash-based runner-brick refractories tested in steel casting experiments

This study presents a novel material concept utilizing pressed rice husk ash (RHA) substrates coated with a chemically inert ceramic barrier via flame-spraying for steel ingot casting. Runner-brick prototypes were successfully fabricated and internally coated by a flame-sprayed alumina layer. An Al 2 O 3 -C interface layer was introduced between the RHA substrate and the flame-sprayed coating to overcome the highly non-linear thermal expansion arising from the α – to β –cristobalite transformation of the RHA substrate. This interface layer effectively accommodated thermal expansion mismatch and prevented cracking of the flame-sprayed coating during heating. The runner-brick prototypes were tested in proof-of-concept casting experiments with steel melt at 1600 °C and successfully withstood the casting process without significant damage or molten steel leakage. The solidified steel blocks were analyzed regarding their population of non-metallic inclusions (NMIs), revealing no drastic change in total NMI counts compared to two state-of-the-art fireclay-based references and showing no indications of coating detachment.