Temperature distribution in laser-clad multi-layers

Results of temperature distribution modeling for multi-layer structures prepared by direct laser remelting of metal powders in an Ar environment were numerically obtained and compared with experimental data. Powders of bronze B10 and stellite SF6 alloys and also base plates of S235JR steel were taken as sample materials. In the experiment a 1.5 kW cw CO2 laser, equipped with a multi-stream nozzle capable of delivering metal powder at a rate of up to 0.2 g/s coaxially with the laser beam, was used. Dimensions of the melted zone and its position relative to the base were obtained from calculation and agreed with the microstructure observation of the sample cross-sections. The model revealed that isotherms at 1020 and 1350 °C penetrate the interfaces to a depth of about 5–10% of the individual layer height for B10 and SF6, respectively. This was confirmed by inspection in a scanning electron microscope (SEM) and also by a depth-dependent X-ray energy-dispersive spectroscopy (XEDS) measurement of the main chemical components of multi-layers, i.e. Fe, Co, Ni (SF6) and Fe, Cu, Sn (B10). Also the cooling rates indicated agreement between modeling and experiment. This allows us to conclude that the model can be applied for preselecting the process parameters.