The use of holographic optical elements (HOE's) to investigate the use of a flat irradiance profile in the control of heat absorption in wire-fed laser cladding

• Holographic optics were used to compare Gaussian and flat square laser beams.
• The flat square beam gave wetting at a reduced power density.
• The flat square beam gave a melt pool at a larger range of power densities.
• Reflectivity calculations studied the effects of incidence angle on heat absorption.
• Beam shape was the primary factor in the heat absorption profile and incidence angles could be used to maximise heat absorption overall.

This work investigates the use of holographic optical elements (HOE's) to control the applied heat profile and thermal absorption of a wire used for laser cladding. The two thermal distributions compared were a circular beam with a Gaussian heat profile (Gaussian beam) and a square beam with a flat profile (pedestal beam). Heat absorption calculations between these were carried out to show the potential differences in absorption, with empirical results created to show how the differences in absorption affect the cladding properties. Micrographs of the clad cross-sections were created using optical microscopy and were analysed with respect to wetting angle and clad dilution. These results were compared to an alternative method of applying an even beam profile; enlarging the Gaussian beam relative to the wire diameter. The results showed that the use of a HOE to create a more even beam profile gave superior wetting behaviour and less dilution.