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The microstructure of high vanadium and cobalt high speed steel(high-V/Co HSS)and the mornhologv of its carbides were analyzed by optical microscope(OM),scanning electron microscope(SEM),electron probe microanalysis (FPMA),X-rav rower diffraction(XRD),atomic force microscopy(AFM)and single phase erosion(SPE).The results suggest that the as-sprayed high-V/Co HSS has fine equiaxed grains(about 20 μm in size),which were homogeneously distributed.The carbides have two classical morphologies: one is fine particles(about 2 μm in size)distributed along the grain ooundanes and the other is needle-like one,distributed on the grain boundaries.There are MC carbides,M2C carbides,M6C carbides and Cr2 WC2 carbides in the as-sprayed high-V/Co HSS samples,however,in the as-cast high-V/Co HSS,there are MC carbides and Cr2 WC2 carbides only.The SPE results show that there are two types of MC carbides in the as-sprayed HSS: the sphere one and the particle-like one.The former is about 2 μm in size and the latter is less than 1 μm,dispersed inside the grains,quite different from the MC carbides in the as-cast HSS.According to the AFM results,the skeleton-like M6C carbides of the as-sprayed high-V/Co HSS are embedded in the matrix along the grain boundaries.It is found that there are sharp membrane pieces on the carbides.Some small bamboo-shoot-like MC carbides grow from the matrix and are dispersed inside the grain.Those larger MC carbides are spherical particles embedded at the grain boundary junctions.