Improving the corrosion resistance and mechanical properties of 2205 duplex stainless steel welded joints by laser cladding CoCrFeNiTiSi high-entropy alloys coating

Abstract

Laser cladded CoCrFeNiTiSi high-entropy alloy (HEA) coatings with excellent comprehensive properties and promising application potential were proposed to improve the corrosion resistance and mechanical properties of 2205 duplex stainless steel (DSS) metal inert gas (MIG) weld joints. The microstructure, the mechanical properties, and the corrosion resistance of the HEAs were investigated systematically by way of scanning electron microscope (SEM), transmission electron microscope (TEM), quasi-static tensile test, and electrochemical test, etc. The laser cladded coatings were composited of FCC and BCC phases and characterized by fine equiaxed grains. Microstructure evolution of cladded coatings was achieved through changing the input current during laser cladding process so as to manipulated the corrosion resistance and mechanical properties, whereas variation was hardly observed in the types of phases in the coatings. As compared with the WM, the pitting corrosion resistance of laser cladded weld metal (LCWM) was significantly improved, which should be attributed to the passivation effect of Cr element in HEA materials. The excellent mechanical properties of LCWM were supposed to be originated from the strengthening effect of refined grains and the formation of BCC phase hindering dislocation movement. Coatings obtained with input current of 340 A had presented the best pitting corrosion resistance while the coatings with input current of 380 A exhibited perfect combination of improved strength and enhanced ductility. The WM was entitled excellent pitting corrosion resistance by laser cladded HEA coatings whereas the traditional soften effect of HAZ was fortunately avoided, which gave birth to a comprehensive improvement in mechanical properties and corrosion resistance.