Microstructure And Mechanical Properties Of Laser Repaired GH4169 Superalloy Assisted By Electromagnetic Stirring

In this paper,GH4169 nickel-base superalloy was used as experimental material,and the microstructures and mechanical properties of laser repairred GH4169 superalloy assisted by electromagnetic stirring were investigated.The solidification microstructures of laser repairred GH4169 superalloy with different magnetic field conditions were observed by analysis method of metallographic microscope and scanning electron microscope.The effects of the main parameters of magnetic field intensity and magnetic field frequency on the laser repaired GH4169 alloy hardness and room temperature tensile properties were studied,obtained the electromagnetic stirring effect of on the mechanical properties of ally.The research result are as follows:The experimental results showed that the effects of electromagnetic stirring repair parts forming good morphology,without obvious defects.With the increase of magnetic field strength and magnetic field frequency,Laves brittleness phase decreased and microsegregation weakened.Microstructure analysis showed that the magnetic field is applied after the original extension of continuous columnar dendrite growth had no obvious change,but the column crystal to a certain extent like grain refinement.Electromagnetic stirring makes the metallurgical defects in road overlap between area and area reduction.When the magnetic field frequency is 100 Hz,the magnetic field strength is 2.0T,the microstructure of the repaired area is the best,but with the further improvement of the auxiliary magnetic field,the effect of magnetic field is weakened.Microstructure analysis showed that with the increasing of magnetic field intensity,the interdendritic eutectic Laves phase by continuous strip become discontinuous and wormlike,Laves volume fraction decreases gradually in the magnetic field is 2.0T,Laves area fraction is 3.85% minimum.720 degrees of aging treatment after 8 hours,when without magnetic stirring,the ?? phases of laser repair GH4169 superalloy are small granular,fuzzy boundaries,the average diameter was about 20 nm and the volume fraction is 60.07%.With the increasing of magnetic field intensity,?? phase gradually into a disc of small diameter.The size of ?? phases becomes larger,when the magnetic field is 2.0T,?? phase particle diameter size reached 33.5nm and volume fraction of69.73%.At the same time,the laser repair of GH4169 alloy in the ?? phase from the disc ?? precipitates gradually become elongated squarethe with magnetic field frequency increases,merge and part of ?? phase particle collision together,becomeirregular in shape.When the magnetic field frequency is 100 Hz,the maximum ?? phase volume fraction is 70.19%.Microhardness tests show that without magnetic field,the average microhardness of deposited samples repair area is 297.9HV and the base metal hardness is 370.9HV.When addition magnetic field,repaired sample sedimentary hardness decreases,and the magnetic field strength is 3.0T phase ratio decreases about 6.9HV when deposited.The sample after aging treatment,the average microhardness of samples without adding magnetic field restoration area is 423.6HV,and the deposited samples increase coMPared to 125.7HV hardness.With the increasing of magnetic field intensity,heat treatment of specimens repaired zone hardness gradually increased.When the magnetic field is 2.0T,the maximum hardness of repair area is 445.2HV.With the increase of magnetic field frequency,the hardness value of the repaired area increases first and then decreases.When the magnetic field frequency is 200 Hz,the minimum hardness of the repair area is 430 HV.The analysis thinks,convection repair sample repair area resulted in magnetic stirring the liquid metal to reduce the content of Laves phase and microhardness decreased,but the change of phase content restoration area less Laves and the hardness decreases little.Alloy element by magnetic field,the dendrite Nb solid solution elements increase the content of aging after heat treatment,the repair area of dendrite stem region precipitation strengthening phase ?? increase in the number of micro hardness was significantly increased.The tensile strength analysis at room temperature shows that the tensile strength of the laser repaired GH4169 alloy increases first and then decreases with the increase of the magnetic field strength.Without electromagnetic stirring condition,the tensile strength is 889.2MPa,elongation is 16.1%,when the magnetic field intensity of 2.0T,frequency of 100 Hz,repair of tensile strength reaches 1045.2MPa,the elongation rate reached 22.7%.When the deposited sample after aging treatment,without electromagnetic stirring conditions,the tensile strength of materials is 1271.2MPa,the elongation is 13.2%,the magnetic field intensity 2.0T,the magnetic field frequency is100 Hz,the maximum tensile strength,restoration tensile strength reaches 1487.8MPa,the elongation rate reached 14.1%,the tensile strength and elongation properties are close to standard forging heat treatment standard.