Microstructural characterisation of laser clad coating of nickel based alloy with dissolved SiCp

A laser surface cladding technique was used to form an Ni-CI-B-Si-C alloy c oating doped with 30 vol.-%SiCp on an AISI 1045 steel substrate. The SiC pa rticles completely dissolved during the melting stage of cladding. The bond ing zone has a microstructure of a gamma-Fe band resulting from epitaxial p lanar growth followed by a cellular dendritic eutectic of gamma-Ni + M-23 ( C, B)(6) on solidification, characterised by directional solidification. Th e microstructure of the cladding layer is composed of very closely spaced n et-like M-23 (C, B)(6) primary dendrites and a small amount of interdendrit ic interdendritic gamma-Ni + M-3(B, Si) lamellar eutectic, and has primary small spherical graphite particles in the upper part of the cladding layer. The rapid solidification involved in the laser cladding resulted in substa ntial extension of solid solubility of Si in the gamma-Ni terminal solid so lution. The M-23 (C, B)(6) primary dendrites contain a high density of stac king faults. The eutectic M-3(B, Si) phase exhibits a periodic structure. M ST/3943.