The fabrication of Fe-W-mullite-based composite coatings inside a steel pipe by centrifugal-SHS process

Fe-W-mullite-based composite coatings were prepared on the inner-surface steel pipe from two reactions of Fe(Mn) WO4-Fe2O3-Al-Si and Fe(Mn) WO4-Fe2O3-B2O3-AlSi mixture powder by centrifugal-SHS process. Standard Gibbs energy minimization method was used to compute the adiabatic temperature (T-ad) and predict equilibrium composition of the products. The composite coatings consisted of two layers of alloy (alpha) and ceramic (beta) which were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with energy-dispersive X-ray (EDX). Surface roughness, hardness, and adhesive strength properties of the coating layer were investigated by profilometer, Vickers microhardness, and compression-shear test, respectively. In addition, the effects of adding Fe to the system was studied. It was found that the composite coating from the reaction of Fe(Mn) WO4-Fe2O3-Al-Si with 1.4 wt% Fe provided the smoothest surface, highest hardness, and adequate adhesive strength.