Abstract:
The joints of K439 B Ni-based supper-alloy,an advanced aircraft engine material,were welded with continuous wave(CW) laser in argon atmosphere.The influence of the welding-rate on the microstructures,deformation and tensile strength was investigated with scanning electron microscopy,X-ray diffraction and energy dispersive spectroscope.The results show that the welding-rate had a major impact.Generally speaking,a faster welding-rate,that is,a lower heat input,produced a narrower welding beam with stronger hardness,comprising equiaxed and columnar grains localized at welding center; as the welding-rate increased,the tensile-strength and elongation-ratio changed in an increase-decrease manner,maximizing at 4 m/min to 852 MPa and 44.5%,respectively.Welded at 4 m/min,the continuous distributions of cellular/equiaxed/columnar grains and quite a few dimples coexisted in the flat compact welded seam,with significant deformation localized at the joints' ends.Shear and cleavage fractures account for the fracture mechanism.