Effect of Nb addition on structure and mechanical properties of FeAl coating

Mild steel was coated by hot-dipping in a molten aluminum bath. The Fe-Al-Nb alloyed coating was prepared by implanting the Nb atoms into the Fe-Al coating using a double-glow plasma surface metallurgy method. The morphology, element distribution and phase composition of the alloyed layer were characterized by OM, SEM/EDX and XRD. Meanwhile, the basic mechanical properties of these two coatings were measured and compared. The results showed that the Nb element exhibited gradient distribution in the Fe-Al coating. And the alloyed layer consisted of pure Nb, Fe2Al5, Fe3Al, AlNb2 and Fe7Nb6 phases. After Nb addition, the microhardness of the Fe-Al coating was improved for the diffusely distributed carbide phases. And the adhesion was enhanced with better plastic deformation. What's more, the nanoindentation tests indicated that the toughness of the Fe-Al coating was improved with a stronger ability to resist plastic deformation and a greater plastic deformation work.