Regulating diamond-induced pores in laser-cladded HEA/diamond coatings by thermal-fluid coupling

초록

This study addresses the preparation of FeCoCrNiAl0.5 high-entropy alloy/diamond @W/Ni composite coatings by laser cladding, and the problem of pore defects due to the change in the temperature field of the molten pool triggered by the ultra-high thermal conductivity of diamond (similar to 2000 W/(mK)) is investigated. It focuses on resultant molten pool temperature-field variations and the formation mechanism and regulation of pore defects. Experiments reveal diamond particles accelerate local melt solidification, inducing characteristic encapsulated pore around diamond. These pores exhibit two distinct morphologies:(1) Pores encapsulating diamond particles, (2) Pores adjacent to but separated from diamonds. Mechanism analysis confirms diamond with high thermal conductivity rapidly dissipates heat, causing localized undercooling and accelerated solidification. This traps gas bubbles near diamonds. Process parameter optimization shows minimal pore density at 1200-1400 W laser power. Lower power (<1200 W) reduces molten pool size and shortens gas escape windows, increasing pore. Higher power (>1400 W) also elevates porosity. A thermal-fluid coupling mechanism for pore formation is proposed, enabling low-defect high entropy alloy/diamond coatings with enhanced interfacial integrity for extreme wear applications.

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