Coating of Aluminium with High Deposition Rates Through Extreme High-Speed Laser Material Deposition

Abstract

Abstract In the past few years, the Extreme High-Speed Laser Material Deposition (EHLA) process has been used as a coating technology alongside conventional processes due to its unique process characteristics and is an economical and sustainable alternative to traditional technologies. The essential characteristic of the process is that the main energy is absorbed by the powder particles so that they reach the substrate surface in a molten state. Thereby, metallurgically bonded and dense wear and corrosion protection coatings are generated. This leads to significantly higher surface and deposition rates can be achieved in comparison to Laser Material Deposition (LMD), and heat-sensitive substrates can be coated. Moreover, in addition to this resource efficiency, the process is not only economically attractive but also sustainable. To reduce component weights as well as secondary energy consumption, aluminium has become an essential base material in most industrial sectors. Aluminium is not simple to process and the wear resistance is small due to the low hardness in comparison to widely used steels. Various technology solutions are currently being investigated for the coating of aluminium. The low melting temperature of aluminium (approx. 750 °C) poses a great challenge when coating with, for example, iron-based alloys. Another challenge for laser-based systems is the reflectance of aluminium in the wavelength range approx. between 1030-1070 nm of conventional laser beam sources. The high degree of reflection of aluminium is the reason why additive processing quiet challenging is. Therefore, for conventional laser-based processes, laser beam sources in other wavelength spectra, e.g. green or blue, are being developed to improve the processing of aluminium. Currently, commercially available multi-kW lasers in the visible light spectrum are still below the available power of IR beam sources. In the context of this study, the feasibility of coating aluminium using EHLA is investigated. A high power 8 kW IR disk laser of the TRUMPF company is used to determine the maximum possible deposition and surface rate.