Investigations on High-Speed PVD technology for deposition of alpha-Al-O+X and Al-Ti-O+X coatings for steel die casting

• Applicant: Professorin Dr.-Ing. Kirsten Bobzin
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 269121028

Meeting the growing challenges of climate change requires a wide range of solutions in mechanical engineering, including the development of new technologies, products, and energy-efficient, resource-saving processes. The reforming manufacturing process is considered resource-efficient, especially for mass production and high-level automation, which is relevant in countries with high labor costs such as Germany. Die casting is a suitable method for plastics and aluminum alloys, but there are no industrially feasible solutions for die casting of refractory alloys. This is mainly due to a lack of economically usable tools that can withstand the high thermal requirements and problems such as welding and corrosion of the tool surface. Cyclic thermal loading during die casting is also a major challenge. In the current research project, promising Al-O+X (X = Cr, Ti) coatings were developed using High-Speed Physical Vapor Deposition (HS-PVD). These coatings successfully prevented metal-physical corrosion and adhesive adherence to the molten steel in initial tests. They also showed high thermal stability. Nevertheless, investigations on the service life under cyclic thermal load in contact with the molten steel are still missing, which will be carried out in the requested follow-up project. With an increase in coating thickness, a reduced compressive residual stress was observed in the HS-PVD coatings, which does not correspond to the expectations of coatings deposited by MS and arc PVD. Accordingly, research is needed to explain this result in more depth and whether there is an influence on the cyclic lifetime of the coating compounds in the molten steel. The overall objective of the research project is to investigate the influence of a defined temperature-time profile on the failure behavior of the coating compounds in direct contact with the molten steel. The service life of the coating compounds for use in steel die casting is to be investigated and quantified in terms of their resistance to cyclic thermal loading in the molten steel. Furthermore, there is insufficient knowledge about the residual stress states in HS-PVD coatings and the correlation of these with the coating and system properties, so there is a great need for research in this area. With this, the influence of residual stresses on the lifetime of the selected coating compounds with varying coating thicknesses is investigated. Deep investigations will be carried out to study failure mechanisms that limit the service life of the coating composites after cyclic contact with the molten steel.

• DFG Programme: Research Grants