Microstructure and hardness of CoNiCrFeTix high-entropy alloy coatings prepared by laser cladding: Combining experimental and molecular dynamics simulation

Laser cladding technology offers several advantages over alternative coating methods, including rapid cooling, low dilution rate, and effective metallurgical bonding between the coating and matrix. However, there is limited understanding regarding the microstructures and properties of laser-cladded high-entropy alloy (HEA) coatings. Thus, our research aims to investigate the characteristics and performance of CoNiCrFeTix (x = 0.1, 0.3, 0.5, 0.7) HEA coatings, produced through laser cladding, on Q235 steel substrates We employ molecular dynamics (MD) simulation and experimental techniques to examine the impact of Ti element content on the structure and hardness of the cladding layer. The MD simulation accurately reproduces the melting and nucleation processes of crystal structures, providing insights beyond what is observable through experiments alone. Our results reveal that the cladding layer is predominantly composed of an FCC phase, with an increasing presence of a BCC phase as the Ti content rises. Correspondingly, experimental observations confirm that the CoNiCrFeTix HEA coating primarily consists of the FCC phase, while FeCr, Ni2Ti, and Co2Ti phases emerge with higher Ti content.The cladding layer exhibits a characteristic dendritic (DR) structure, where the interdendritic (ID) region expands as Ti content increases. Additionally, we conducted surface hardness testing on the cladding layer. The hardness of the cladding layer increases with the increase of Ti content, and the increase in Ti content enhances the stability of the dislocation density in the cladding layer.