An improved gas nozzle for laser surface alloying

An experimental research project was undertaken to characterize the flow field surrounding the molten metal during laser alloying. In addition, an objective of this project was to design a protective gas nozzle system for laser alloying that would control the entrainment of the outside gas, provide a gentle pressure to the molten metal and not adversely effect the alloying process. Existing nozzle geometries were selected for evaluation in a water tunnel simulation. The water tunnel simulation visualized a complex, three-dimensional oblique flow field, which was created by the Nd:YAG's optics/gas delivery package being configured 15 degrees from normal to the work surface to prevent reflection back into the optics. From the water tunnel simulation two geometries were characterized in gas trials with argon, nitrogen and helium gases. A convergent (conic) geometry and divergent geometry were evaluated by measuring the pressure field and oxygen content impinging on an instrumented flat plate. A divergent nozzle geometry was used in creating laser alloyed surfaces, and those surfaces were examined for oxygen content.