The surfacing layers with different boron（B）element content are obtained by adding different amounts of boron carbide（B4 C） powder into the self-shield surfacing with flux-cored wire powder. Metallographic observation shows that the matrix of surfacing layer is a composite structure consisting of austenite and martensite,a eutectic component（Mo,Cr,Fe,Nb）2 B interruptedly distributes along the grain boundary. The hardness and wear resistance of surfacing layer can be improved by solid solution strengthening effect,but metastable phase δ-ferrite causes the crack in surfacing layer. After aging treatment at 500 ℃,the metastable δ-ferrite will transform into the σ-ferrite,which can effectively prevent cracks and improve the hardness and wear resistance of surfacing layer. The optimum addition of boron carbide（B4 C） in powder is 1.5%,the maximum hardness is 47 HRC,and the wear resistance is 3 times higher than that of the surfacing layer obtained by flux-cored wire without element B. Using this wire as a surfacing material to repair the stop valve can prolong its service life and has good corrosion resistance and high economic value.