A Novel Approach to Regulate the Microstructure of Laser-Clad Fecrnimnal High Entropy Alloy Via Ceo2 Nanoparticles

Abstract

In this work, the mechanical mixing process was successfully used to inoculate FeCrNiMnAl powder with CeO2 nanoparticles, which contributed to the heterogeneous nucleation of fine equiaxed grains. In this way, the nano-CeO2/FeCrNiMnAl HEA composite coating with low dilution, cracks-free was successfully fabricated. The microstructure of nano-CeO2/FeCrNiMnAl HEA composite coatings exhibited homogenous, fine-grained and equiaxed. To explore the effect of CeO2 on the microstructure, this work reveals the columnar-to-equiaxed transition (CET) behavior of HEA coating during solidification process. As a comparison, the heterogeneous nucleation behavior of fine equiaxed grains induced by nano-CeO2 in HEA composite coatings was studies. The results showed that CeO2 nanoparticles were enriched at the grain boundaries of HEA composite coating, and it not only had a drag effect, but also hindered the growth and development of grains. However, excessive nano-CeO2 could affect the forming quality of HEA coating and have a negative impact on the mechanical properties. After regulating the grain structure, the mechanical properties of HEA composite coating have been greatly improved. While 1.0 wt.% nano-CeO2 was added, the microhardness of HEA composite coating reached to the maximum (670.4 HV0.2). Compared with substrate, the average microhardness has increased almost 91.5%. The friction performance of 1.0 wt.% CeO2/FeCrNiMnAl HEA composite coating was the optimal as well and the wear rate reached 3.12×10-6 mm3/N m. The oxidized enamel layer was produced on the worn surface of HEA composite coating.

Keywords: Laser cladding, CeO2 nanoparticles, High entropy alloy coatings, Heterogeneous nucleation, Grain refinement.