Preparation Of The Iron-based Superalloy Cladding And Research On Its Microstructure And Properties

When hot die works,the temperature of its surface can reach to 500 ?,which can lead to emergence of oxidation and softening.In this condition,wear failure is very likely to occur.Combining service environment of hot die,design philosophy of gradient overlay is adopted in this paper.Iron-based superalloy,used as buffer layer material,is optimized in wear resistance through TIG arc welding gradient overlay orthogonal experiment.the performance of the coating material were studied by means of OM,EPMA,XRD,microhardness,temper resistance,high-temperature oxidation resistance are tested to characterize the of the gradient overlays' properties.Comprehensive analysis of experimental results are done.It can be seen that the microstructures of orthogonal group cladding layers are mainly composed of intragranular dendrites ?-Fe,discontinuous intergranular ?-Fe and dispersive intermetallic compound,with a few punctiform special carbides in grain boundaries.Adding of Cr,W,Mo and other alloy elements can increase the amount of precipitated intermetallic compound.(Fe,Ni)solid solution exists as the matrix phase in 1A,3C,10J's coatings.Fe2Ni3,FeNi and Cr2Ni3 can also be detected.Three overlay are welded.Composition of coating surface is close to designed components,which show a high pick-up rate of alloy elements.In 10 J cladding,pick-up rates of Cr,Ni are respectively 78%,73.5%,while it's higher in 1A cladding,reaching 82% of Cr and 75.6% of Ni.The optimized iron-based superalloy,cladding 11K(15% Cr-2% Mo-6% W),is chosen by tempering test.Result of high temperature tempering test shows that:Compared to 10 J,tempering resistance of partial orthogonal coating enhanced after adding alloying elements;After 700 ? tempering,the hardness(346 HV0.1)of 1A coating is the highest in the orthogonal group,improving about 50 HV0.1 and 82HV0.1 respectively compared with the basic formula cladding 10 J and H13 steel;The hardness(349 HV0.1)of optimized 11 K coating is higher than 1A cladding.In oxidation experiments of 600 ? and 700 ?,11 K coating shows excellent high-temperature oxidation resistance whose oxidation weight gain mass per unit area is only 1/8,1/3 of H13 steel respectively.Taking orthogonal optimization formula 11 K coating as the transition of gradient cladding,11 K coating with WC and Cr3C2 as reinforced surface of gradient coatings,12 L and 13 M gradient coatings sample are prepared.The phase composition of gradient coating surface consists of iron-based solid solution,carbides and intermetallic compound,which are dispersed and precipitated in the matrix.Transition claddings and H13 steel substrate materials have formed a good metallurgical bond.The result of hardness test shows that: Adding of carbides has greatly improved the iron-based superalloy's hardness;The hardness of 12 L and 13 Mare almost same;surface coating is about 3mm in thickness,540 HV0.1 in micro-hardness value;2 mm under cladding surface shows no hardness drop substantially;Influenced by dilution rate,coating hardness approaching transition is about 410 HV0.1.Sediment wear test result shows that: Carbide reinforced gradient coating surface has excellent abrasion resistance,Cr3C2-reinforced 13 M has best relative wear resistance,which is about 1.75 times of H13 steel and 1.9 of 11K;The12L coating's relative wear resistance is about 1.48 times of H13.