Research On Flux Cored Wire And Gradient Die Arc Additive Manufacturing For Hot-forging Die Of Engine Superalloy Disk

At present,hot-forging die is mainly forged by ingot + machining or precision casting.The die manufactured by these method is made of single material.When serving in the harsh environment of high temperature and high pressure for a long time,it is prone to deformation,cracks,spalling and other damages,which makes the service life of the die low.Aiming at the shortage of low life of die made of single material at present,the gradient structure of die was manufactured by Wire and Arc Additive Manufacturing(WAAM),which improved the service life of die.According to the structural characteristics of superalloy disk die for aeroplane engine,a three-layer gradient structure die with bottom layer,transition layer and hardfacing layer was designed,and three metal flux cored wires,which included bottom layer,transition layer and hardfacing layer,were developed.The bottom layer was designed with the same alloy composition as 5CrNiMo die steel,but the content of C was reduced and the content of Cr and Mo was increased,which made the bottom layer have good crack resistance and toughness.The composition design of transition layer alloy was based on the bottom layer,in which the content of C,Cr and Mo was increased,and appropriate amount of V,W and Nb was added to make it have better mechanical properties.The composition design of hardfacing layer was based on the transition layer,in which the content of C,Cr,Mo,V,W and Nb was increased,which could improve the high temperature mechanical properties and wear resistance of hardfacing layer.In addition,1% NaF was added to all three metal flux cored wires to improve arc stability and process performance.Three kinds of metal flux cored wires had good formability,and the spatter rate was less than 2.5% under different process parameters.The arc was stable during the WAAM by observed in high-speed video.The microstructure of deposited metal of bottom layer metal flux cored wire was fine ferrite + bainite;the microstructure of deposited metal of transition layer metal flux cored wire was fine ferrite + pearlite + a small amount of lath martensite with fine hard phase carbide dispersed in it;the microstructure of deposited metal of hardfacing metal flux cored wire was lath martensite + retained austenite with fine hard phase carbides.The tensile strength of hardfacing metal deposits was 1404 MPa at 700?.The wear weight loss rate was 0.11%,which was 35.29% lower than that of 5CrNiMo.Hardfacing metal had good wear resistance at high temperature.The interfacial bonding strength between the bottom layer and 5CrNiMo matrix was 1013 MPa,the interfacial bonding strength between the transition layer and the bottom layer was 1162 MPa,and the interfacial bonding strength between the hardfacing layer and the transition layer was 1317 MPa.The bonding strength of the adjacent gradient layer was good and had high bonding strength.Three kinds of metal flux cored wires were deposited on 5CrNiMo to form gradient structure samples.The results showed that the hardness of 5CrNiMo was 245 HV,the tensile strength of 5CrNiMo was 1005MPa;the hardness of bottom layer was 345 HV,the tensile strength of bottom layer was 1145MPa;the hardness of transition layer was 455 HV,the tensile strength of transition layer was 1311MPa;the hardness of hardfacing layer was 550 HV and the tensile strength of hardfacing layer was 1436 MPa.The gradient structural die could be constructed by accumulating three kinds of metal flux cored wires on 5CrNiMo.The path planning strategy of planar slicing and offset filling was adopted.Robot programming language was obtained through Java programming to realize gradient WAAM of superalloy disk dies for aero-aircraft engines.The dimension deviation of die manufactured by WAAM was less than 1mm,and no cracks or fusion defects were found.The practical application showed that the gradient structure die had a high service life.