Pitting corrosion mechanism of BCC+FCC dual-phase structured laser cladding FeCoCrNiAl0.5Ti0.5 HEAs coating

This work elaborated the microstructure and corrosion behaviors of laser cladding (LC) FeCoCrNiAl0.5Ti0.5 high-entropy alloys (HEAs) coating on AISI 1045 steel substrate. It revealed that the LC FeCoCrNiAl0.5Ti0.5 HEAs coatings were composed of dendritic region (DR) and interdendritic region (IR). Furthermore, DR was mainly composed of BCC phase while IR was composed of FCC phase. There was also the transformation of BCC to L21 structure detected due to the addition of Ti element. Due to the uniform microstructure and addition of corrosion-resistant elements (such as Cr), the dual-phase HEAs coatings exhibited pretty good corrosion resistance. A dense passive film would form during the corrosion process to protect the inner structure. It was demonstrated that the corrosion rate of the coating was only 32.8% of that of the substrate. However, the pores formed during the LC process on the surface might be the initial site for pitting corrosion.