Effect of laser cladding on forming qualities of YCF101 alloy powder in the different lap joint modes

Abstract

This paper studies the different lap joint methods of YCF101 alloy powder by direct laser fabrication (DLF) technology and analyzes the structure, porosity, cracks, and surface topography of multichannel forming parts fabricated by DLF to optimize the ideal lap joint mode. The selection basis of lap joint modes is based on the surface adhesion powder of single-layer cladding surface, inner cracks and porosity, and microstructure of the forming parts under different scanning modes. Regardless of any scanning method, there would be obvious sticky powder at the lap joint, and the pore and cracks are mainly present at the lap joint. The uneven energy density of the weld during the fusion process makes a great difference in the microstructure of the molten pool and the lap joint, the structure of molten pool is small isometric crystal, and the structure of lap joint is bulky dendrite. The defects caused by the uneven energy distribution and sticky powder had been improved by different lap joint modes between layers. The uniform distribution of the linear trace poles at the outer contour surface improved the surface quality of the forming part. As the mesh size of the cladding region that is divided by the cladding trajectory becomes smaller, the quality of forming parts has changed. The double decussation and outline mode has the smallest mesh size, the porosity is 0.47%, the microstructure of the lap joint area is no longer just dendrites, there appears isometric crystal and structure refining, the crack reduces, and the compressive strength is improved. To some extent, the problem brought by sticking powder and uneven heat distribution had been worked out.