Search

Inconel718 superalloy samples with V-grooves were experimentally repaired by electromagnetic stirring assisted laser repairing (EMS-LR) under different magnetic field currents. The effects of the magnetic field current on morphologies of single pass repaired zone (RZ), microstructure and mechanical properties of multilayer RZ were experimentally investigated. Microstructure observations show that metallurgical bonding is obtained between the RZ and the substrate when the optimized process parameter is used. The microstructure in RZ is coarse columnar crystal when no electromagnetic stirring is used, which grows epitaxially along the deposition direction. With the increase of magnetic field current, the convection of liquid metals prompts the transformation from coarse columnar to fine equiaxed grains. The strong scour of liquid metal convection can affect the interdendritic γ+Laves eutectic reaction and prohibit the growth of Laves phase. Electromagnetic stirring can improve the spreading of liquid metal in a certain extent. The width and deposition height of the single trace were measured and it is found that the width and deposition height ratio changes from 3.26 when no electromagnetic stirring is used to 3.33, 4.14 and 5.14 when the applied magnetic field current is 20, 40 and 60 A, respectively, and the penetration is found to be decreased inversely. The tensile strengths of repaired components increase from 487 MPa to 510, 673 and 770 MPa for magnetic field currents of 0, 20, 40 and 60 A, respectively.

The effects of the solution treatment temperature on the microstructure, the chemical composition homogeneity and the microhardness of laser solid forming GH4169 superalloy were investigated. It is found that the grain boundaries become clearer with increasing of the solution treatment temperature. The recrystallization occurs when the samples are solution treated at 1000–1170 °C for 1 h; when the solution treatment temperature is higher than 1000 °C, a large number of twin crystals can be observed, and the grains are refined remarkably compared with the as-deposited grains. The chemical homogeneity can be achieved through solution treatment at 1100 °C for 1 h. With increasing of the solution treatment temperature, the microhardness first decreases rapidly, and then slowly when the solution treatment temperature is above 1100 °C. The variation of microhardness can be explained based on the precipitation behaviors of γ′, γ″ and δ phases during the solution treatment. It is concluded that the temperature of 1100 °C is the low limit of solution treatment temperature range for laser solid forming GH4169 superalloy.