Abstract: Two methods were used to control the size of in-situ synthesized NbC in Fe-Cr-B-C-Nb hardfacing alloy. The size of carbide in four kinds of Fe-Cr-B-C-Nb hardfacing alloys, with niobium content of 2.2%,3.2%,3.9%,and 5.0%,respectively, were studied in this paper. A new kind of wear-resistant alloy,with dispersed micro/submicron NbC,was in-situ synthesized by plasma cladding. The results show that the size of NbC could be controlled,and increasing niobium content increased the size of in-situ synthesized NbC,and the carbide tended to agglomerate. The cooling conditions played an important role in controlling the size of carbide. The size of NbC decreased with water cooling,but would increase when the cooling rate decreased.