Nickel-base Superalloy K423A GTAW Repair Processand Numerical Simulation Reasearch

Because of the advantage of excellent corrosion resistance, high melting pointand high temperature, the K423A Nickel-based superalloy has been widely used inaero-engine manufacturing as high temperature resistant material. Due to theimmature technology research, it is easy to appear osteoporosis, loose and otherdefects during the process of the whole casting K423A alloy parts in domestic.GTAW is relatively mature welding method in the process of material processingapplication at present, it can be more precisely controlled heat input and has beenwidely used in high temperature alloy welding.In order to meet the repair requirement of K423A Nickel-based superalloy withcasting defects, the basic repairing technology on GTAW of K423A Nickel-basedsuperalloy was studied in this paper. Meanwhile, the temperature and stress field ofdifferent welding current during the process of GTAW were analyzed by the finiteelement numerical simulation.The FEM software ANSYS10.0was employed to calculate the temperature fieldand stress field of GTAW, the welding current of40A,60A and80A was continuousloaded for25seconds, then temperature field and the changes of cooling to35second’s stress field were simultaneously analyzed. The results show that themaximum temperature rise rapidly of welding district center by increasing the time ofrepair welding, and the temperature rise rate decreased with increasing time. Themaximum temperature of work-piece surface reached1682℃,1829℃and1976℃in K423A Nickel-based superalloy when heat load to25second. The stress fieldshows that stress is small on the parent metal near the repair welding area whencooling to35second. The simulation results show that tensile stress is mainlyconcentrated in the base material far from welding zone, contemporary the local areaof fusion welding zone lines also appeared higher tensile and compressive stresses.The highest of tensile stress is765Mpa and the highest of compressive stresses is803Mpa when using80A repair welding current, which result in stress concentrationand cracks appearance. It turn out that60A repair welding current is preferablyparameter. The study of K423A alloy GTAW repair welding process shows that, whenwelding voltage is10V, protective gas is15L/min in positive side and protective gasis15L/min in reverse side, non-fusion, incomplete penetration, cracks and other welddefects are observed with the repair welding current of40A,50A and70A. Whilethere are no welding defects by using the repair welding current of60A. Weldingdefects are easily observed in reverse side without protective gas in the repair weldingprocess. A large number of Si, C segregation are found along the grain boundary,which cause the generation of welding cracks by using the HGH3536wire as the fillermaterial. Nevertheless, HGH3113welding wire is ideal filling material, with whichuniform distribution of each phase and good repair welding results are acquired.