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Melting and Transfer Behaviours of Filler Wire Acted by a Laser Heat Source
G-X. Su, Y. Shi, M. Zhu and G. Zhang

Laser cladding with filler wire is a cost-competitive approach over powder-based feeding systems; however, the practical application of it in the industry has been limited seriously because of the complicated interaction between the laser and the wire. Single clad deposition of E501T-1 low alloy steel filler wire was made on 4 mm thick Q235 carbon steel substrate using a large-sized spot high power diode laser (HPDL) laser. The typical position relationships of the laser beam and the filler wire were calibrated by mathematical calculation firstly. Then the process maps indicating the melting mechanics of filler wire and the stable cladding process at different cladding conditions were developed. Lastly, based on the high speed camera system, the relationships between the melting and transfer behaviours of filler wire and the formation of deposition layer were revealed. The results showed that there were two typical melting mechanisms of filler wire. And the transfer behaviours of liquid metal could be decomposed into large droplet transfer, liquid-bridge transfer, and spreading transfer mode. The stable cladding process and well-formed deposition layer could be obtained while liquid metal was transferred into the molten pool with a liquid-bridge. Comparing with other laser-wire positions, the laser energy and filler wire interacted with each other more sufficiently and the liquid bridge transfer mode could be formed in a larger process window while the filler wire was partially covered by the laser beam. The most ideal distance between the laser beam and filler wire was zero.

Keywords: High power diode laser (HPDL), Q235 carbon steel, E501T-1 low alloy steel filler wire, laser cladding, melting mechanisms, transfer behaviours, deposition layer

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