Fining grain of FGH95 nickel-based superalloy laser cladding layer by ultrasonic impact treatment

FGH95 nickel-based superalloy laser cladding layer was strengthened by ultrasonic impact treatment(UIT). The microstructure of laser cladding with and without UIT was studied by metallurgical microscope, the grain size was calculated by the Image-Pro Plus software, and the sectional microhardness of laser cladding was also analyzed after UIT. Results show that plastic deformation of cladding layer was formed with UIT and the varying degrees of grain refined behavior were obvious in depth direction. Dislocation pile up phenomenon was significant in strong plastic deformation zone with refined small crystal block. Sub-plastic deformation zone was depth range of 0.1-0.25 mm and the microstructure of this zone was refinement tree dendrite. The microstructure of micro-plastic deformation zone was mainly refined equiaxed grains into 5.4μm depth to 0.7 mm. The microhardness of cladding layer was enhanced significantly and the maximum value of surface microhardness was 594.25 HV by 1.3 fold after UIT.