Synthesis and characterization of composite coating in AlFe2O3-Cr2O3-NiO system applied by combined method of combustion and centrifugal synthesis

In this study, using aluminothermic auto-combustion system and rotation of a hollow tube of plain carbon steel (centrifugal force), a stainless steel coating was applied on the inner surfaces of the tube. In this regard, the homogenized samples of powder mixtures in the desired ratio in Al-Fe2O3-Cr2O3-NiO -and Al-Fe2O3 -Cr2O3 systems were subjected first, to thermal analysis and then, the centrifugal coating process. The results obtained from the thermal analysis indicated the possibility of the formation of iron aluminide and the metallic phase with composition approximately to stainless steel in addition to aluminum oxide. The results of phase analysis and microstructural observations of coated sample showed the formation of a two-layer composite coating including the metal phase of stainless steel with the chemical composition of Fe-19%Wt Cr11%Wt Ni (similar to stainless steel 304) as the underlying phase and alumina ceramic phase as the surface phase. In s ome cases, intermetallic compounds was also formed as an intermediary layer, which increased the compatibility of these two underlying and surface phases of metal and ceramic. Due to the presence of ceramic phase and intermetallic compounds in the coating, its hardness reached values higher than 1260 HV.