Design of cost-effective Fe-based amorphous coating alloys having high amorphous forming ability by thermodynamic calculation

In this study, new cost-effective Fe-based amorphous coating alloys having high amorphous forming ability were developed by varying the Fe content, while their microstructure, hardness, and corrosion resistance were also evaluated. Chemical compositions that have the lowest driving force of formation of crystalline phases such as Fe3P, Fe3C, and α-Fe were obtained from thermodynamically calculated phase diagrams of the representative FexAl2(P10.83C7.47B1.7)98-x alloy system at a crystallization temperature of 443 °C. Considering the intersections of driving force curves of Fe3P and Fe3C, Fe3P and α-Fe, and Fe3C and α-Fe, the Fe contents were found to be 77.8, 76.2, and 75.8 at.%, respectively. The microstructural analysis results of 1.5-mm-diameter suction-cast Fe-based alloys indicated that the Fe76.5Al2(P10.83C7.47B1.7)21.5 alloy had a fully amorphous microstructure, whereas crystalline phases were formed in other alloys. This alloy showed a better hardness and corrosion resistance than conventional thermal spray coating alloys, and its production cost could also be reduced by using less expensive alloying elements, which could provide a good way to practically apply this alloy to Fe-based amorphous thermal spray coatings.