Archive: Dec 2018

Titled Puddle Forming and Shaping with Primary and Secondary Lasers.

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Titanova was just awarded the patent, Titled Puddle Forming and Shaping with Primary and Secondary Lasers.  This Patent is available for licensing.

Description or Summary of Invention

So for one skilled in the art of welding one can appreciate the advantage of being able to shape the puddle such that the bead  of the final solidified bead is improved on flat areas, on edges and inside corners and is amenable to tie-in to subsequent laser cladding  tracks. The shape control is achieved by an additional laser beams that are strategically place in location to pull the weld puddle by either affecting surface tension or keeping it molten longer in strategic locations.  The shape control can also be used to steer the weld puddle around hole or to repair holes or blow outs during cladding. The puddle steering is achieved by changing the surface tension on the surface of the puddle in strategic locations thus affecting the puddle shape and subsequent thickness.

This patent intends to solve or improve upon the following

  • Deposition Efficiency [Watts/kg] or [ Kg/hr]
  • In situ defect mitigation [ fixing blow holes]
  • Edge definition
  • Edge definition around holes
  • Inside fillet definition
  • Lowering dilution
  • Thinner clads
  • Improved morphology [flatter thinner clads]
  • Control of solidification cracking issues
  • Improving wire feed laser cladding

Fluidity Control

The clad puddle fluidity affects the dilution and the clad deposition morphology as is the case with laser additive manufacturing.   These two characteristics, low dilution and good morphology of laser cladding presently are not simultaneously achievable at high deposition rates.  Clad dilution decreases with higher deposition rates which lead to unacceptable clad morphologies. One needs to slow down and put more energy into the workpiece to “wet-out” the clad and tie into the previous pass as with the case with laser weld overlays.  One needs to significantly reduce deposition rates and simultaneously use smaller laser beams in order to achieve acceptable 3D laser additive profile. The surface tension or fluidity of the laser clad puddle affects the final clad profile. i.e. “The bigger the puddle the less control”.    Besides the chemical make-up of the clad material, it has been demonstrated that beam intensity distribution is the biggest contributor to surface fluidity.  It has been shown and modeled that fluid motion results from surface tension gradient and gravity gradients caused by temperature variations in the melt resulting in a stirring motion in the laser cladding puddle.  The directions of the fluid motion are strongly influenced by the laser beam heating the liquid surface. These induced vortexes are a large contributor to dilution. Titanova’ s patent addresses this problem to achieve high deposition rates and surface area coverage, while at the same time preserving the excellent surface morphology.

 

This will enhance the economic viability of this process by making the high deposition rates with smooth flat clads and 3D laser additive consistently achievable on all material compositions.  Understanding and controlling the surface tension in-situ will be key for enabling an increase in deposition rates [kg/hour, m^3/hour] and surface coverage rates [m^2/ hour] on a variety of surfaces and shapes, while at the same time preserving the superb surface smoothness and low dilutions.  This will make the diode laser processing even more economically competitive with existing weld overlay and 3D additive processes.