| Inertial friction welding(IFW)is an advanced solid-state connection technology with advantages of high welding speed,simple process,less parameters,and stable joint performance.It can avoid the defects of melting-solidification caused by joint melting under high temperature in welding process to reduce the material damage.It has been widely used in the whole manufacturing field of aircraft engine at home and abroad,especially in the whole manufacturing field of turbine rotor.The FGH98 alloy material developed in our country is the third-generation nickel-based powder superalloy with high strength and damage tolerance,which is used in high push-weight ratio aeronautical engine disk shaft.Therefore,it is significantly instructive to research inertial friction welder and joint microstructure and properties of FGH98 alloy for engine turbine rotor working under high temperature and achieving integral structure.In this experiment,the FGH98 alloy with hollow structure was welded by inertial friction welding,and the inertial friction welding joint was subjected to an aging treatment.The specific research contents were as follows:Firstly,the range of welding parameters were determined by the superiority of joint with hollow structure and the formula of welding parameters:speed was more than 800r/min,the minimum value of top forging pressure was 2500PSI,and moment of inertia was1150lb·ft~2.Five groups of welding parameters were obtained according to the actual welding process,of which were analyzed the influence on forming quality and defects of joints.The results shown that the increase of pressure in top forging process had greater influence on the metallurgical bonding of joints compared with that of flywheel speed.Therefore,only using the higher pressure in top forging matched with appropriate flywheel speed can an excellent joint be obtained.The variation of temperature field,stress field and plastic flow field in the model of inertial friction welding process of FGH98 alloy was established and analyzed by using DEFORM finite element software.It turned out that the finite element model can characterize the welding process well,and the better welding joint can be obtained under the fifth set of parameters:900 r/min,2900PSI,and 1150lb·ft~2.Using this parameters,the distribution law of temperature field,stress field and plastic flow field in the simulation process is consistent.The values shown an upward trend at the beginning of friction welding,a peak value at the stable friction stage,and a downward trend at the late stage of friction welding.To obtain good structure and excellent performance,the aging heat treatment was conducted to the better inertial welding mentioned above.Consequently,the influence of aging heat treatment on the grain evolution mechanism,??phase distribution and comprehensive mechanical properties of the joint were studied.The results shown that the aging treatment had no significant effect on the grain evolution in each region of the joint,only the grain size was slightly larger than that in the welding state.The grain evolution was original grain,deformed grain,and isometric fine grain in base metal zone,thermal influence zone and welding core zone successively.The dynamic recrystallization process was from non-dynamic recrystallization,partial dynamic re-crystallization to complete dynamic re-crystallization successively.Processed the aging heat treatment,the secondary??phase increases in each region of the joint and the three??phases had begun to occur.The microhardness of the HAZ 0.4mm away from the center of the joint reaches a peak of568HV under aging condition,which was 66HV higher than that under welding condition.The high-temperature mechanical properties had been greatly affected as well.The tensile strength was increased from 86%to 95%,elongation after break and section shrinkage were increased,and the durable life was also increased to 94%of the base metal,which confirmed that the??phase of the multiple size in the joint after aging treatment can significantly improve the comprehensive mechanical properties. |
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