| Duplex stainless steel has the advantages of both ferritic stainless steel and austenitic stainless steel,with its superior combination of mechanical and corrosion properties.It is widely used in many fields such as petrochemical,papermaking,marine engineering.In this paper,for the high-performance DSS coatings,we prepared Nb-alloying DSS coatings and Nb-alloying Nickel-free DSS coatings with laser cladding technology.The microstructure and properties of coatings were systematically characterized by the spectrometer,X-ray diffraction(XRD),scanning electron microscope(SEM),microhardness tester,universal material testing machine,friction and wear tester,and electrochemical workstation.The main research contents are as follows:(1)Nb-alloying(0?1.5 wt.%)coatings were obtained by using laser cladding technology,and the effects of alloying element were studied.The results indicated that Nb-free coating was mainly composed of ferrite and austenite.With the addition of Nb,the microstructures refined,Nb(C,N)precipitated,and the content of ferrite increased,which improve the microhardness of the coatings.With the content of Nb increased,the tensile strength and yield strength of the coatings increased,while the ductility of those increased first and then decreased.When the content of Nb was 0.25%,the elongation was the best,which is 36.4%.The coefficient of friction decreased after adding Nb,which reduces the time to enter the stable wear stage under wear conditions.The addition of Nb improved the corrosion resistance of the coatings.When the Nb content was 1.5%,the corrosion resistance was the best.The corrosion potential was-187.3 m V,and the corrosion current density was 0.5791×10-6A·cm-2.(2)The effects of Nb-alloying(0?1.0 wt.%)and heat treatment on the microstructure and properties of the Nickel-free DSS cladding coatings were investigated.The obtained results showed that as-cladded Nb-free coating was mainly composed of ferrite and austenite.The microhardness,tensile strength,yield strength,and ductility of that were288.5 HV0.2,847.2 MPa,678 MPa,and 27.9%,respectively.With the addition of Nb,the microstructure refined,the content of ferrite increased and Nb(C,N)precipitated.With the increase of Nb content,the microhardness,tensile strength,yield strength and corrosion resistance of as-cladded coatings improved first and then got worse,while the ductility of those continued to decline.When the content of Nb was 0.25%,the best tensile property,tensile strength was 890.9 MPa and the yield strength was 748 MPa,was obtained.The addition of Nb improved the wear performance of as-cladded coatings.After solution treatment at1100?for 1 h,homogeneous distribution was obtained and the content of austenite increased.The tensile strength and yield strength both decreased,while the ductility significantly improved,the elongation of Nb-free coating increased to 46.7%.The wear performance of coatings and the corrosion resistance of part of the coatings further improved.When the Nb content was 0.25%,the corrosion resistance was the best.The corrosion potential was-290.9 m V,and the corrosion current density was 0.5298×10-6A·cm-2. |
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