Coaxial Laser Cladding of Cobalt-Base Alloy Stellite™ 6 on Grey Cast Iron Analysis of the Microstructural and Mechanical Properties Depending on the Laser Power

Abstract

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. 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. Coatings dilution or composition depends directly on the laser power as well as bead geometry. 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 Cr7C3 and Cr23C6 as well as blocky tungsten carbide W2C. Coating hardness depends on the chemical composition and microstructure that is modified by the deposition parameters. Low laser power results in high carbide fraction and most refined microstructures, accounting for harder coatings.