Effect Of Mo, Mo-Nb Microalloying On Microstructure And Properties Of Cr20Ni80 Alloy

Cr20Ni80 alloy,as one of nickel-based electrothermal alloys,has a single austenite structure from room temperature to high temperature and no magnetism at room temperature.It has many advantages,such as uniform and stable resistivity,low thermal expansion coefficient,high melting point,good high temperature strength,high temperature oxidation resistance and excellent mechanical p roperties.Widely used in household appliances,industrial furnaces and other fields,it has becomed the focus and hot spot of research in the field of electrothermal alloys in recent years.The research of electrothermal alloys in China has been developed for many years.Although China has become a big producer of electrothermal alloys,there is still a big gap in the properties of Cr20Ni80 alloys produced abroad.Considering that most researchers have studied the effect of rare earth elements on the perfo rmance of electrothermal alloys in the past,few studies have been done to improve the performance of electrothermal alloys by means of metal microalloying with high melting point.Therefore,the method of microalloying is adopted in this paper.The effect of microalloying elements on the structure and properties of Cr20Ni80 alloy was studied by adding different contents of high melting point Mo and Nb elements into Cr20Ni80 alloy.The research results may provide basic data for the future production of electrothermal alloys.In this research,Cr20Ni80 alloy was prepared by WK-? vacuum arc furnace melting.The microstructure of the alloy was analyzed by means of optical microscopy(OM),scanning electron microscopy(SEM)and electron probe microanalysis(WPMA).Hardness,resistivity and mechanical properties of Cr20Ni80 alloy w ere tested by Vickers hardness tester,SB220 DC resistance tester and Shimadzu tensile tester.The main results are as follows:(1)The effects of Mo and its contents(0%,0.3%,0.5%,1.0%)on the microstructure and properties of Cr20Ni80 alloy were studie d.The results show that Mo element can refine the grain size of Cr20Ni80 alloy.With the increase of Mo content,the grain size of the alloy decreases,Increased inclusion content resistivity increases,Vickers hardness increases first and then decreases,tensile strength at room temperature and high temperature increases first and then decreases,and elongation after fracture decreases.When the content of Mo is 0.5%,the resistivity is 1.183 ??·m,the Vickers hardness is 272.5 HV,the room temperature ten sile strength is 540 MPa,the high temperature tensile strength is 169 MPa,and the macroscopic fracture characteristic is plastic fracture.(2)The effects of Nb,Mo and their contents(0,0.3%Nb-0.5%Mo,0.5%Nb-0.5%Mo,1.0%Nb-0.5%Mo)on the microstructure and properties of Cr20Ni80 alloy were studied.The results show that Mo element can refine the grain size of Cr20Ni80 alloy.With the increase of Nb and Mo content,the grain size refinement,Increased inclusion content resistivity,Vickers hardness,tensile strength at room temperature and high temperature increase,and elongation decreases after fracture.When the content of Nb and Mo is 1.0%-0.5%,the resistivity is 1.247??·m,the Vickers hardness is 289 HV,the room temperature tensile strength is 571 MPa,the high temperature tensile strength is 189 MPa,and the macroscopic fracture characteristic is plastic fracture.