Study On Microstructure And Properties Of Laser Cladding 718 Alloy Cladding Layer By Rare Earth

Laser cladding technology is widely used in the preparation of compound coatin g and metal coating parts and quick-wear part repair and manufacturing because of the small heat effect of substrate materials,substrate characteristics of small deformation degree and higher production efficiency.The 718 alloy has good high temperature strength,high oxidation resistance,corrosion resistance and other excellent performance,which widely used in aerospace engine,gas turbine,turbine engine components,usually using in the bad working environment.To improve its performance,so will the introduction of the 718 alloy laser cladding parts surface repair,surface modification and remanufacturing,which can obtain good economic benefit.Rare earth oxides have excellent purification,metamorphism,improv ing tissue and alloying effect.With rare earth oxides on modification,laser cladding alloy718 can improve the corrosion resistance of alloy,high temperature oxidation resistance,etc.In this article,laser cladding is used to obtain the Inconel 718 alloy cladding layer with different content of rare earth oxides Ce O₂ and La₂O₃.The SEM,EDS,OM and X-ray were used to investigate the microstructure,morphology,phase structure,and the elemental content change,composition distribution and microstructure characteristics of the cladding layer of the 718 alloy.The microhardness of the cladding layer was measured,and the oxidation resistance of the718 Alloy Cladding Layer under the high temperature environment of 1000?and the corrosion resistance at room temperature were tested respectively.The effects of the addition of rare earth oxides on the microstructure and properties of the laser cladding718 alloy cladding layer were analyzed and discussed.The results show that:1.The addition of two different types of rare earth oxides Ce O ₂ and La₂O₃ to the718 Alloy powder can form a good metallurgical bond between the cladding layer and the 45 steel matrix.After adding rare earth oxides,the surface quality of the 718 alloy cladding layer is significantly optimized,the microstructure is even m ore uniform and compact,and the content of Laves phase in the cladding layer decreases.It shows that the segregation of Nb in the cladding layer after adding rare earth oxide has been weakened.2.With the addition of two kinds of rare earth oxides Ce O ₂ and La₂O₃,the phase composition and structure of the 718 Alloy have changed obviously.The 718 alloy cladding layers without rare earth oxides are composed mainly of elements such as?Fe,Ni?,Cu_3.8Ni,Cu Ni₂Ti,(Nb_0.03Ti_0.97)Ni₃ and other elements such as iron,copper,titanium and niobium.New phases such as Cu₄Ti₃,La₅Si₃ and other La compounds were found in the cladding layer obtained by adding rare earth oxides La ₂O₃.Besides?Fe,Ni?,Cu_3.8Ni,Cu Ni₂Ti,(Nb_0.03Ti_0.97)Ni₃ and other compounds in the cladding,a new phase of a trace Cu_3.8Ni and a compound of Ce are also formed.At the same time,after adding 0.7%La₂O₃,the Fe,Cr and Mo in the cladding layer were diffused in the cladding layer after adding 0.7%La₂O₃,while Ni,Nb spread to the cladding layer.After adding 0.6%Ce O₂,the Fe in the cladding layer was promoted,and the Cr element was diffused in the cladding layer,and the content of the two elements decreased,and the content of Ni,Mo and Nb in the cladding layer was higher than that in the matrix.The microhardness of the surface of the cladding 718 alloy was obviously improved,and the hardness changed to uniform and stable.3.By 1000?,100 h after high temperature oxidation,compared with the cladding layer without adding rare earth oxides and adding rare earth oxide Ce O₂ and La₂O₃ alloy cladding layer formed on the surface of the oxide film thickness uniformity,organization,main phase composition is?Ni,Zn,Fe?Fe₂O₄,?Ni,Co?Cr₂O₄,Cu Mn₂O₄ oxide spinel structure.The cladding layer oxidation weight curve changes quite gentle,which show that adding rare earth oxide can significantly improve the laser cladding of 718 alloy cladding layer of high temperature oxidation resistance.Moreover,the high temperature oxidati on resistance of the cladding layer was the best when the content of La₂O₃ was 0.7%and the content of Ce O₂ was 0.6%.4.The acid corrosion resistance of the cladding layer is significantly enhanced after adding rare earth oxide Ce O₂ and La₂O₃,compared with the 718 alloy cladding layer without adding rare earth oxides at room temperature in 5%dilute sulfuric acid environment.When the La₂O₃ content is 0.7%and the Ce O₂ content is 0.6%,the corrosion resistance of the cladding layer is the best.The effects of the types and content of different rare earth oxides on the microstructure and properties of the cladding layer of laser cladding 718 Alloy were comprehensive analyzed.The addition of the proper content of rare earth oxides was beneficial to improve the surface quality of the cladding layer,improv ing the segregation of niobium,improving the oxidation resistance and acid corrosion resistance of the cladding layer.Compared with other rare earth oxide content,add0.7%wt.La₂O₃ and 0.6%wt.of Ce O₂ the comprehensive performance of cladding layer is best.And the comprehensive performance of the former is higher than that of the latter.