Océane Gillet, Sergio Pace, CRM Group, Liège, Belgium
Physical Vapor Deposition (PVD) processes still have an image as a “high tech” technology not really suitable for an industry like steel making. Usually, PVD technologies are used within a range of nanometers. Typically in the steel industry coatings as thick as several microns are required. The most well-known example is the Jet Vapor Deposition (JVD) technology developed by the CRMGroup for ArcelorMittal. This process enables the continuous high-speed deposition of evaporated Zn onto steel coils. This process has been industrialized since 2016 in Liège and has already produced over one million tons of coated coils. Building on this success, a new breakthrough process industrialization has been launched in the CRMGroup: Electron Beam Physical Vapor Deposition (EB-PVD). EB-PVD is a vacuum deposition technique that has the potential to produce thick coatings (several microns) of different materials at a high evaporation rate. This technology is already used in a wide range of applications, such as surface treatments for aeronautical parts (with the evaporation of technical ceramics like thermal barrier coatings). The aim of this presentation is to show the technological challenges that need to be tackled and resolved to ensure the successful industrialization of EB-PVD technology for the continuous thick coating of metal coils within the steel industry. The CRMGroup is equipped with a vacuum pilot coating line (PVD Pilot Line) as a key process development tool. It provides a link between the developments made at laboratory scale and their implementation within the industry. This extraordinary tool has previously provided technical solutions during the industrialization of the JVD process. With the know-how and the experience of the steel industry and its constraints, the challenge is to bring EB-PVD technology to the industrial-scale using the PVD Pilot Line tool. There are multiple key levers for the successful industrialization of EB-PVD technology. The most important of these: both achieving long term operation and the efficient management of transients (line speed variations and different coatings thickness requirements). On one side, our internally-developed continuous feeding solution is providing encouraging results in its ability manage the crucible bath liquid level stability over long periods. On another front, the implementation of an on-line XRF in addition to the quartz microbalance data collected allow for the continuous tracking of the coating thickness in real time. The conclusion will highlight the remaining challenges in order to achieve industrial and production success for EB-PVD technology.