CrNiMo duplex stainless steel surfacing layers with Co content of 0%,1%,2% and 3% are prepared on 304 austenitic stainless steel substrate by TIG powder surfacing.After solution treatment at 1100℃,the effect of Co content on the microstructures,hardness and corrosion resistance of CrNiMo duplex stainless steel is studied by metallographic observation,microhardness test,potentiodynamic polarization curve and electrochemical impedance spectroscopy（EIS）.The results show that with the increase of Co content,the proportion of austenite phase increases from 52% to 61% and then decreases to 41%,and the morphology of austenite phase changes from strip-like or island-like to grid-like;the solid solution of Co element in the matrix promotes the precipitation of Cr-rich and Mo-rich intermetallic phases,improves the hardness of the surfacing layer,destroys the stability of the passivation film,and weakens the corrosion resistance of the surfacing layer.