Work carried out on the laser cladding of Stellite™ 6 so far has been focused on the effects of laser processing parameters on the clad geometry, evolution of microstructure, hardness, and wear resistance with steel as substrate (Ref 1, 2, 3, 4, 5, 6, 7). The remaining liquid solidifies by a eutectic reaction into an interdendritic lamellar mixture of β-Co and Cr rich carbides, depending on alloy composition and laser cladding process parameters (Ref 2, 10). For a C content lower than 2 wt.%, the first phase of the microstructure to form is dendritic β-Co with a metastable face-centered cubic (fcc) crystal lattice at ambient temperature (Ref 5). The refractory metals, Mo and W are solid solution hardening elements (Ref 7), while the content of C contributes to the strength via precipitation hardening by forming carbides and intermetallic phases (Ref 5). The application of Stellite™ 6 involves huge cost and laser surface cladding may be a viable option for its cost-effective utilization to extend the functionality and performance limit of conventionally used grey cast iron (EN-GJLP-200) as brake disk in mechanical protection (friction, wear), barrier function (corrosion resistance), and optical properties (reflection, absorption) (Ref 3, 6, 7, 8).Ĭo-28Cr-4.5W-1.2C wt.% are the main constituents of Stellite™ 6 in which Cr provides corrosion resistance while carbides add strength (Ref 9). Low laser power results in high carbide fraction and most refined microstructures, accounting for harder coatings.Ĭo-based hardfacing alloys like Stellite™ 6 are used in surface engineering for applications requiring outstanding sliding wear, oxidation, and corrosion resistance during service at elevated temperatures such as under aggressive operating conditions in the petrochemistry, nuclear reactors or food processing facilities (Ref 1, 2, 3, 4, 5, 6). Coating hardness depends on the chemical composition and microstructure that is modified by the deposition parameters. The typical microstructure of the coatings comprises a solid solution of α (hcp)- and β (fcc)-Co with a dendritic structure as a metal matrix and an interdendritic lamellar eutectic, which contains predominantly β-Co, chromium carbides Cr 7C 3 and Cr 23C 6 as well as blocky tungsten carbide W 2C. Coatings dilution or composition depends directly on the laser power as well as bead geometry. In this article, we have focused on a detailed quantitative analysis of the effect of different laser powers (1.5, 2.0, 2.5, 3.0, 3.5, and 4.0 kW) on the bead geometry, dilution, microstructure, and hardness. A high-power diode laser was used to generate single- and multi-bead coatings of Stellite™ 6 by coaxial laser cladding over flat grey cast iron (EN-GJLP-200) as a preliminary study to develop a wear and corrosion resistant coating for brake disks on a cost-effective substrate.
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