Laser cladded Tribaloy T-800 coatings are highly prized for extreme-condition applications but suffer from severe cracking susceptibility due to the excessive precipitation of brittle primary Laves phases, which severely limits their wear-resistant service reliability. This study addresses this critical issue via Ni alloying and systematically elucidates the underlying mechanisms of crack mitigation and wear property evolution. We demonstrate that Ni addition fundamentally alters the solidification pathway. Thermodynamic calculations and experimental validations reveal that increasing Ni to 20 wt.% compresses the primary Laves phase formation temperature range from 125 °C to a mere 27 °C. Coupled with the high cooling rate of laser cladding, this kinetic undercooling effectively bypasses the primary precipitation stage, promoting a fine Laves/γ-Co lamellar eutectic structure. Finite element simulations corroborate that this microstructural transformation, alongside the increased volume fraction of the ductile γ-Co/Ni solid solution, drastically reduces crack susceptibility from 0.9119 to 0 by effectively relieving intense residual tensile stresses (up to 729.5 MPa) via dislocation multiplication and crystallographic slip, which blunts crack tips. Intriguingly, despite a moderate reduction in macro-hardness from 787.3 HV0.3 to 674.4 HV0.3, the 20Ni coating achieves a low wear rate of 1.187×10-5 mm3·N⁻¹·m⁻¹, along with a significantly reduced and stable friction coefficient of 0.3648. This exceptional tribological performance arises from a synergistic strengthening-toughening mechanism: the hard Laves lamellae provide wear resistance, while the soft γ-Co/Ni lamellae accommodate deformation and promote the formation of a protective lubricious oxide tribofilm, effectively suppressing brittle spallation. This work provides a novel, industrially viable pathway for designing crack-free, wear-resistant Co-based composite coatings for demanding tribological applications.

Laser cladding; Nickel alloying; Eutectic microstructure; Crack susceptibility; Wear resistance