Perspectives for Conventional Coating Processes Using High-Speed Laser Cladding

Abstract

Abstract The most commonly used surface protection technologies against wear and corrosion are electrochemical hard chromium plating or thermal spraying. But these coating technologies have limits. Additionally, due to health concerns, hard chromium plating is under increasingly restrictive use in Germany, the European Union, and the Asian market. One technology which is currently under investigation for replacing conventional coating processes, e.g., plating in these instances is the high-speed laser cladding. Using high-speed laser cladding (high-speed laser metal deposition, HS-LMD), which is a DED (directed energy deposition) process, a laser beam is heating powder particles, which are fed coaxially into the laser beam, to nearly melting temperature before these particles hit the surface. Using a laser as the heat source, the heat input into the workpiece can be minimized. This allows a very low dilution of additive material into workpiece—typically < 10 µm—and high feed rates between 100 and 500 m/min can be achieved. Layers generated by this process can be locally adjusted in thickness between 50 and 300 µm per layer. Since each layer is metallurgically bonded to the metallic substrate or the adjacent layer before, multi layers or multi-material approaches are feasible. By use of the aforementioned unique process features, new and in properties tailored coating systems become possible. HS-LMD might be a promising candidate for replacement of hard chromium plating, for example, large rotational symmetric parts. In this paper, we have selected Rockit®401 as a hard, corrosion-resistant, and nearly “cracking-proof” material. Additionally, we have chosen the corrosion resistant Inconel® 625. We will investigate the influence of high surface rates on properties such as defects, hardness, and crack susceptibility, as well as achievable layer thicknesses.