Laser cladding using high-power diode lasers

Abstract

Currently, intricate problems of surface treatment can be solved through precision cladding using advanced laser technology. However, the high price of CO₂ and Nd:YAG lasers, the effort required for beam guiding as well as the low absorption of the CO₂ irradiation limit the applications. In light of this, a new and promising solution is provided by the current availability of high-power diode lasers: it makes laser cladding essentially more efficient and practicable. By one-step cladding with a 1.4 kW diode laser, protection layers of Co-based alloys, a carbide-reinforced Ni alloy, and alumina can be deposited onto steels and aluminium-based light alloys. The width of single tracks is up to 5 mm, with a layer thickness of 0.2 to 1.5 mm. For tasks of repair and remanufacturing, multilayer stacking of metal alloys can be easily performed. The layers are dense and with a fine dendritic structure and are metallurgically or chemically bonded to the substrate. For the Co- and Ni-based alloys, the cladding rate is 0.5 kg/h. This high value is due to the higher absorption degree of the 0.94 μm diode irradiation compared to the 10.6 μm CO₂ irradiation. Comparison of the cladding results for tracks produced with CO₂ and diode lasers has shown that 1.4 kW diode power is equivalent to 3.9 kW CO₂ laser power. Thus, the absorption obviously increases by a factor of at least 2.5. In addition to the higher efficiency, the resulting tracks appear to be of better quality. Thus far, examples of applications are the repair of wear-damaged punches and dies, and the hardfacing of engine valves.