Effect of laser energy density on the microstructure and properties of Tribaloy T-800 coating fabricated by laser cladding on the DZ125 alloy

Tribaloy T-800 coatings are fabricated on the DZ125 alloy by laser cladding, and the effect of laser energy density (η) on the macroscopic morphology, phase composition, microstructure, microhardness and the wear properties of the coatings is investigated. The experimental results indicate that cracks are observed in the coating fabricated with the laser energy density η1 = 33 J/mm2. However, as the laser energy density is raised to η2 = 50 J/mm2 and η3 = 75 J/mm2, the coatings become crack-free. The coatings consist mainly of face-centered cubic Co solid solution and Laves phase (Co3Mo2Si). The microstructure consists mainly of planar crystal, flower-like Laves phase, coarse Laves phase and lamellar eutectic structure. The average microhardness of the coatings is 717 HV0.5, 673 HV0.5 and 572 HV0.5 for laser energy densities of η1 = 33 J/mm2, η2 = 50 J/mm2 and η3 = 75 J/mm2, respectively. The wear mechanism of the coating fabricated with laser energy density η1 = 33 J/mm2 includes abrasive wear, fatigue wear and oxidative wear. However, as the η is increased to 50 J/mm2 and 75 J/mm2, the wear mechanism shifts to abrasive wear and oxidative wear.