Comparison of the Laser-Repairing Features of TC4 Titanium Alloy with Different Repaired Layers

The laser repairing of TC4 holes was successfully performed with three and five layers under 2.5 mm and 1.0 mm diameters of laser spot, respectively. Experimental and numerical simulations were employed to clarify the influence of the repaired layers on microstructure, residual stress and strength. Optimized parameters were selected based on satisfactory formations. For the laser-repairing process with three layers, optimized parameters were selected as 1100 W laser power, 0.6 m/min scanning speed and 5 g/min powder feeding rate. For the laser-repairing process with five layers, optimized parameters were 800 W laser power, 0.9 m/min scanning speed and 3.5 g/min powder feeding rate. Numerical simulation showed that higher residual stress and larger repairing deformation would be produced when five repairing layers were adopted due to a more severe thermal accumulation effect. The microstructure from the TC4 matrix to the repaired area was orderly lamellar α phase + intercrystalline β phase-basketweave structure-martensite structure-widmannstatten structure. Tensile test results showed that higher tensile strength (910.5 MPa) would be obtained when three repaired layers were adopted.