Catalysis effect of rare earth element Ce on paste boriding treatment of AISI 410 steel

Abstract

Abstract Surface hardening techniques of steel are of great practical interest for applications in various industrial sectors. Boriding is one of the most economical choices. However, the chief deterrent to the widespread application of the technique is the difficulty in attaining a thick, dense boride layer. To solve this problem, a paste boriding process was performed on the surface of AISI 410 steel by introducing 6 wt.% CeO2 addition into the boriding agent. The microstructure of the boride layer is comprised of (Fe, Cr)B and (Fe, Cr)2B, which lie in the external and internal layers of the boride layer, respectively. CeO2 addition makes it possible to prepare a thick, dense boride layer on the surface of the steel substrate, thereby improving both wear and corrosion resistance of the steel. The catalysis mechanism of the rare earth element Ce can be ascribed to three aspects. First, CeO2 addition can take part in the chemical reactions involved in the boriding process to produce more active boron atoms. Second, Ce can facilitate the adsorption of active boron atoms onto the surface of the steel through preventing the formation of iron oxides on the steel’s surface. Third, Ce can diffuse into the surface of the steel and generate severe lattice distortion due to large atomic size, thereby promoting the boron diffusion. These results provide a high-quality, low-cost pathway for the surface hardening of steel in practical industrial applications.