Influence of High-Temperature Substrate Preheating on Laser Cladding of Stellite 6 onto Inconel 718 Alloy

Laser cladding is a modern surface treatment process used for the regeneration of damaged components and deposition of coatings for protection against corrosion and wear. Precise process control enables the production of claddings on small surfaces (<1 cm²). However, in some cases (e.g., cladding of turbine blades), there is a limited possibility of heat dissipation into the substrate material, which causes its rapid heating to several hundred degrees Celsius. This work's objective is to determine the effect of the substrate temperature and laser cladding parameters of a Stellite 6 cobalt-based alloy on the Inconel 718 nickel-based alloy substrate on the geometry of a single cladding track, as well as its microstructure and hardness. Laser cladding with Stellite 6 powder was performed using an Yb:YAG TruDisk 1000 laser. The varied process parameters included the laser beam power density, cladding speed, and powder flow rate. The samples were preheated using a chamber furnace to a temperature ranging from 20 to 800 °C. The geometry of the single tracks produced by laser cladding and the substrate material dilution ratio were determined by measurements conducted on their cross-sections. Further microstructure investigations were performed by means of electron microscopy (SEM). Additionally, hardness measurements (HV0.3) were conducted on the cross-section of each cladded track. It was found that a higher substrate temperature causes melt pool widening and increases the melt depth, while the height of the single cladded track remains only slightly altered. These phenomena lead to the excessive dilution of the substrate material in the cladding (>35%) and result in a decrease in its hardness to the values characteristic of the Inconel 718 substrate (395 HV0.3).