Effect of Laser Parameters on Geometry of Cladded Stellite 6 on 35CrMo Steel Substrate and its Characterization

In this research, laser cladding of Stellite 6 on the 35CrMo substrate was done. Various parameters of the laser caldding process were studied and after optimization of the parameters, microstructure and microhardness were evaluated. Characterization of the cladded layer was done by scanning electron microscope, X-ray diffraction, and Vickers microhardness. The results show that the clad track height was dependent on the parameters of the powder feeding rate and the laser scanning speed, and the laser power had the minimal effect. Similarly, the clad track width was controlled by the laser power and laser scanning speed. The clad track dilution was proportional to the laser power and had the greatest impact compared to other parameters. The wetting angle was controlled by three parameters: laser power, laser scanning speed, and powder feeding rate. Laser power of 550 W, powder feeding rate of 0.6 g/s, and laser scanning speed of 10 mm/s were chosen as the optimal parameters. The results showed a good metallurgical bonding between the cladding and the substrate. The microstructure of the single clad track was dense and crack- and pore-free, and due to the thermal and concentration gradient changes during solidification, it consisted of three different areas, including planar, columnar dendritic, and equiaxed dendritic microstructures. A significant improvement in the microhardness of Stellite 6 cladding was observed as compared with the substrate. By increasing the overlapping ratio from 30 to 60%, the dilution rate decreased from 31 to 7%. As a result, the microhardness reached 361 HV in the overlapping ratio of 30% and further to 452 HV in the overlapping ratio of 60%. The overlapping ratio of 60% between adjacent passes created the best results.