Effect of Co on the corrosion resistance and erosion-corrosion behavior of duplex stainless steel surfacing layer

In the present work, CrNiMoCo duplex stainless steel (DSS) surfacing layers with Co content of 0, 1, 2, and 3% were prepared on AISI 316L substrate by TIG welding powder surfacing. The DSS was tested in the flowing water with sand particles using jet impingement equipment. The effect of Co on the microstructure and erosion-corrosion behavior of DSS was studied via microstructure observation, hardness test, and electrochemical polarization. The results showed 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 addition of Co worsened the corrosion resistance of CrNiMoCo DSS surfacing layer. Co element was dissolved in the matrix to form solid solution strengthening, which increase the hardness of the material. The excellent resistance to erosion-corrosion was related to the excellent mechanical properties that were adjusted by the Co content.