Microstructure and thermal physical parameters of Ni60-Cr₃C₂ composite coating by laser cladding

Abstract

To satisfy performance and long life requirements for hot forging die, Ni60-Cr₃C₂ composite coatings were prepared on the high-speed steel W₆Mo₅Cr₄V₂ using laser cladding technology. Laser clad coatings with different ratios of Ni60:Cr₃C₂ were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX) and microhardness tester, respectively. Specific heat capacity and thermal conductivity were measured by Laser Thermal Constant Meter. Thermal expansion coefficient and elastic modulus were measured by Dynamic Mechanical Thermal Analyzer and Electro-Hydraulic Servocontrolled Testing System, respectively. The results indicated that Ni60+50wt% Cr₃C₂ composite coating had dense and homogeneous structure, as well as a metallurgical bonding with the substrate. With the increase of Cr₃C₂ content, volume of chromium-containing compounds in the composite coating increased, microhardness increased and microstructure refined. The thermal physical parameters results showed that Ni60+ 50wt% Cr₃C₂ composite coating was overall worse than W₆Mo₅Cr₄V₂, but had a higher hot yield strength to alleviate hot fatigue and surface hot wear of hot forging die during hot forging and thus improve the service life of hot forging die.

Keywords

laser cladding / thermal physical parameters / hot forging die / microstructure

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