Optimization of microstructure and properties of laser sintered Ni30Cr25Al15Co15Mo5Ti5Y5 high-entropy alloy coatings via controlling plasma

An active suppressing method of laser-induced plasma was proposed to optimize the crystal structure and tribological properties for the surface laser sintering (SLS) of Ni30Cr25Al15Co15Mo5Ti5Y5 high-entropy alloy (HEA) coatings using a pulsed laser with various shielding gases. The results indicate that electron temperature (Te) and the plasma jet volume with no shielding gas or in He atmosphere were higher than those in Ar−He atmosphere. Well- defined phase transitions and significant metal atom diffusion occurred in SLS, and metallurgical bonding occurred with the precipitation of α-AlFe3, α-AlNi, and γ-AlFe2Ni. The lower energy absorbed by the plasma via inverse bremsstrahlung (IB) strengthened interactions between laser and HEA, increasing the microhardness, and reducing the dynamic friction coefficient. This elucidates the crucial influence of plasma control on laser-based additive manufacturing.