Robotic fiber laser cladding of steel substrate with iron-based metallic powder

The investigations of robotized laser cladding of mild steel by iron-based powder and the study of process parameters on quality and properties of the test surface layers are described. The test surface layers were produced as single stringer beads by means of a laser head coupled with powder-delivering nozzles and mounted on a welding robot arm. The fiber laser emitting at 1.06÷1.07 μm with maximum output power 3.0 kW was used in the study. As the substrate for cladding, the mild steel was chosen, while the experimental powder was composed of 7.0 wt. % of molybdenum, 4.0 wt. % of chromium, 2.0 wt. % of tungsten and vanadium, and also 0.8÷1.0 wt. % of carbon. The surface layers were produced at different laser powers and different scanning speeds. The area of the melt pool and the surrounding regions were protected by argon flow. The detailed influence of the heat input of cladding on the geometry of single stringer beads of surface layers was determined. Results of the investigations showed that the microstructure of surface layers is homogeneous and fine-grained with dispersive precipitation of very fine carbides. Hardness of the mild steel substrate is in the range of 120 to 150 HV1, while the hardness in surface layer is significantly increased up to 800 HV1. The produced surface layers are characterized by high quality. No significant imperfections or discontinuity such pores or cracks were found.