Influence of Cu shell on the anomalous WC grain growth in Ni-base brazed cladding

In vacuum infiltration of Ni-based self-fluxing alloy (NiCrBSi) cladding, reinforced with ultrafine WC particles with average particle size (APS) of 0.2–0.4 μm, several plate-like anomalous WC grains were observed with size of greater than 20 μm. To prevent this anomalous grain growth, Cu shells were coated on WC particles. The very low solid state solubility of WC in copper phase at high temperature can lead to no anomalous WC grain growth. Cu shell with a thickness about 30–50 nm was deposited by means of electroless plating on ultrafine WC particles. The microstructural features of Cu-coated carbides and the resultant brazed claddings were characterized by field emission scanning electron microscopy (FESEM) equipped with energy dispersive X-ray spectroscopy (EDS). The evaluation of the brazed cladding revealed a thick ultrafine grained-microstructure with homogeneous grain size distribution, in contrast to the bare WC-based cermet cladding. The hardness of this novel composite cladding was nearly increased up to 1500 HV, which was 40% more than that of the un-coated WC reinforced cladding. The results demonstrated that the resistance against crack initiation and propagation considerably improved by using Cu-coated WC particles in the sintered media. •To prevent anomalous WC grain growth in Ni based cladding, Cu shell was coated on WC particles by electroless deposition.•The very low solid state solubility of WC in copper phase at high temperature led to no anomalous WC grain growth.•A fine microstructure with homogeneous grain size distribution was obtained in Cu-coated WC reinforced Ni based cladding.•The hardness of this cladding was increased up to 1500 HV, 40% more than that of uncoated WC reinforced Ni base cladding.•The resistance against crack initiation and propagation was considerably improved in Cu-coated WC reinforced Ni based cladding.