Laser cladding of Ni-Cr3C2/(Ni+Cr) composite coating

Laser clad coatings of Ni alloy as well as a composite made from 50 wt% Cr3C2 particles coated with a Ni-Cr alloy and Ni-base alloy on steel 1045 were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX) and microhardness tests, respectively. The effects of microstructure obtained by varying the laser process parameters on the microhardness profile along the depth were studied in the two kinds of clad layers. The results showed that a strengthened surface layer was produced on steel 1045 by laser incorporation of Cr3C2 particles, which increased the hardness of the surface layer by 350-400 HV. The presence of undissolved Cr3C2 particles, the formation of dense dendrites surrounded by a fine eutectic and the precipitation of Cr7C3, Fe-23(C, B)(6) compounds during rapid solidification after the laser treatments were thought to be the main factors for the strengthening of the composite coating. (C) 1998 Elsevier Science S.A. All rights reserved.