Design and realisation of a triple gas cladding head for high-power active fibre lasers

This paper addresses the study, design and realisation of a gas cladding head specifically designed for high-power active fibre lasers. The new cladding head has a coaxial architecture and is able to manage three different gases with three different roles in the coaxial cones. From the central cone to the external cone, the roles of the three gases are as follows: - The first gas (inner gas) is used to protect the focusing lens and control the atmosphere of the molten pool in the cladding to protect and change the final cladding proprieties, - The second gas (central gas) is the powder feeder, and - The last gas (outer gas) is used to shield the work area and increase the process efficiency (to avoid wasting the powder). The new laser cladding head is specifically designed to emphasise the active fibre laser characteristics, such as the small divergence of the fibre beam. The new triple gas head was tested in a long experiment in which the cladding of worn dies used in a hot stamping process for automotive components was repaired. The laser source used in the experiment was an IPG Photonics active fibre laser (1000-W maximum power, 400-micron delivery fibre). The die was made of H13 steel and had considerable dimensions (approximately 450x300x150 mm3). The worn features of the dies were previously milled, and the cavities were filled via laser cladding with Stellite 21.