Study on the effect of ZrC and CNTs particles on Inconel 625 coatings fabricated by coaxial-wire-feed laser cladding

In order to investigate the effect of coaxial-feed laser cladding with the addition of ZrC and CNTs reinforcing particles, a four-split-beam coaxial-wire-feed system was used for the first time to fabricate the cladding layers. Specifically, the effects of the reinforcing particles on the microstructure, mechanical and corrosion properties of the cladding layers were investigated. On 316L substrates, three types of cladding layers were created: pure Inconel 625, Inconel 625 with ZrC, and Inconel 625 with ZrC-CNTs. The testing findings revealed that the cladding layer with reinforcement particles added possessed the ideal geometrical features of large melt width and low dilution rate. Due to the coaxial action of the laser and the wire, the grains on both sides of the single-bead cladding layer transited from columnar crystals to equiaxial crystals along the temperature gradient, and the grains in the middle of the single-bead cladding layer showed the competing growth of columnar crystals and equiaxial crystals at the fusion line. The addition of ZrC and CNTs particles produced a heterogeneous nucleation effect that refined the grain size and homogenized the grain orientation, which CNTs accentuated. Compared with the pure Inconel 625 cladding, the tensile strength of the ZrC/Inconel 625 cladding increased from 731Mpa to 783Mpa, the hardness increased by 29%, and the electrochemical corrosion rate decreased by 53.6%. The elongation of the ZrC-CNTs/Inconel 625 cladding increased from 13.4% to 24%, but the corrosion resistance decreased significantly.