Exchange of experience between designers, engineers, developers and coaters in Chemnitz
The event organized by the European Thin Films Research Association (www.efds.org) at the Fraunhofer Institute for Machine Tools and Forming Technology IWU in Chemnitz also presented current research topics at the Fraunhofer Institute. These included new fields of technology in forming and machining technology.
The workshop
Tools and components are subject to very complex stresses, which often occur simultaneously, such as corrosion, wear and friction. Added to this are aspects of optical properties or haptics. These diverse requirements can often only be achieved with coatings. The workshop was dedicated to this topic. In addition to an overview of plasma coating processes and the coating systems that can be deposited with them, specific solutions for different areas of application were presented:
- Tools for forming technology and plastics processing
- Components for vehicle construction, medical technology, mechanical engineering or decorative purposes
Despite the diversity of applications, the solutions and stresses are often similar, so that all participants were able to benefit from the synergies. The aim of the workshop was to bring together designers and constructors of tools and components as well as development engineers and technologists in coating technology from a wide range of application areas and to discuss the current state of the art, trends and new requirements for research and development.
In addition to the workshop, the event also included a tour of the MERGE Technology Center, a visit to the Fraunhofer IWU and a get-together in the Ratsstube restaurant. The following is a brief report on some of the contributions.
The presentations
The workshop began with an overview presentation to introduce the topic. Prof. Kirsten Bobzin, Institute for Surface Technology (IOT) at RWTH Aachen University, spoke on the subject of "Properties and processes for multifunctional coatings". With individual or combinations of surface technology processes (PVD, CVD, electroplating, sol gel, thermal spraying, etc.), material and component surfaces can be provided with customized functional layers (decor, barrier, electrical conduction, wear and corrosion protection, etc., single or multilayers). The lecturer demonstrated this using applications such as PVD gear coating, water-repellent microstructured plastics (lotus leaf effect), which are created by combining PVD and laser structuring, and thermally sprayed multilayer heating coatings for mold making.
"Cromatipic - an environmentally friendly chromium (VI)-free alternative for metallizing plastics" - Dr. Philipp Immich, Hauzer Techno Coating Venlo, Netherlands, explained the principle of the process, in which a UV-curing coating is first applied to the plastic surface in a 2-step process and then a thin chrome layer is applied using PVD. A matt appearance can be achieved by adding fillers, while an additional SiOx top layer increases abrasion resistance. The Cromatipic® Inline concept is designed for industrial series processes and meets the applicable industry standards.
can be met.
"Application of hard coatings using 3D-capable low-temperature CVD" - Vanessa Frettlöh, Kunststoff Institut Lüdenscheid, was able to show in her paper that the gap mobility of a low-temperature MO-CVD process (precursor W(CO)6) is significantly better compared to PVD processes. This enables a wear-resistant coating of complex geometries with an aspect ratio of at least 1:2.5, which was demonstrated using the example of the deposition of hard coatings based on tungsten carbide. The process temperature of approx. 350°C is not critical for tools, the coatings achieved are hard, abrasion-resistant and can also be easily removed (decoated).
Dr. Jörg Vetter, Oerlikon Balzers Coating Germany GmbH, Bergisch Gladbach, then presented "The latest coating solutions for forming technology". As PVD coatings are always significantly harder than the underlying substrate (steel or carbide), which can lead to the coating breaking through, duplex coatings (e.g. arc + PVD) are a suitable solution. The speaker presented the various BALINIT systems and then went on to discuss Oerlikon Balzers' S3p® process. The "Scalable pulsed power plasma", a combination of arc evaporation and sputtering, is characterized by scalable pulse length and current intensity, excellent control of the pulse shape and covers a considerably wider parameter window compared to conventional HiPIMS. It enables customized coatings for many applications with revolutionary smoothness.
Punching tools are often required to guarantee consistent quality over quantities in the millions and are practically a "maintenance-free tool". Dr. Martin Heß, Fritz Stepper GmbH & Co KG, Pforzheim, presented "Strategies for minimizing wear in high-performance progressive die stamping tools" in his lecture. Coating hardness in particular is an important factor for production batch sizes in the 8 to 9-digit range. In addition to the mechanical and tribochemical properties of the wear protection layer, its resistance to shear stress plays a key role. High-performance magnetron sputtering (e.g. HIPIMS) and the resulting super-hard to ultra-hard, smooth and sufficiently thick coatings appear to be very promising. Fritz Stepper is currently producing "3 µm ta-C" using PLD (Pulsed Laser Deposition). PVD systems and coatings are being discussed as an addition to the in-house system portfolio.
"CVD and PVD coatings for forming tools - processes, benefits, challenges". Dipl.-Ing. Stefan Kaufmann Dörrenberg Edelstahl GmbH, Engelskirchen, introduced the various wear mechanisms (adhesion, abrasion, surface disintegration, fatigue, tribochemical reaction) and then discussed measures against wear. These include wear-inhibiting coating systems produced using PVD hybrid technology. In this process, plasma nitriding (supporting effect for the hard material layer) and PVD coating (hard material layer) are combined in one process. This significantly increases the pressure resistance of the tools. It can be helpful to introduce compressive stresses into the surfaces, e.g. by plasma nitriding, to prevent surface disintegration. It is also always important to take into account dimensional changes caused by coating and heat treatment. The lecturer demonstrated the use of PVD hybrid technology using several examples.
Christian Schotten, Schotten Oberflächenservice, Remscheid, provided information on the topic of "Tool surface pre-treatment and innovative PVD "hardur" thin-film systems for carbide, e.g. for forming tools". The company offers coating expertise for thin to thick layers, the range of processes extends from PVD, CVD, PACVD, plasma processes to hard metal layers (Hardide, Hardur solid), thermal spray coatings (HVOF/HVAF, plasma, arc) and sliding layers to improve demolding (Dicronite-PTFE). Surface finishing is also a focal point. Application examples rounded off the presentation.
"Press hardening as an innovative lightweight manufacturing technology, combined with the highest demands on the tribological system in high-temperature forming technology" - In a joint presentation, Frank Schieck (Fraunhofer IWU, Chemnitz) and Markus Mejauschek (Fraunhofer IST, Braunschweig) provided information on the sheet metal hot forming process of press hardening (form hardening), in which both the forming and the heat treatment of the workpiece take place in a single process step. The sheet metal blanks or closed profiles heated above austenitizing temperature are formed in a cooled tool and rapidly cooled at the same time. The heat treatment integrated into the forming process produces a martensitic microstructure, so that the press-hardened components have very high tensile strengths of up to 1900 MPa. Wear protection also plays an important role in tool optimization. The various wear mechanisms (overheating, abrasion, adhesion, cracking, corrosion) can be mitigated by plasma nitriding and/or coating. Boriding is also being investigated as a new approach, which can be used to achieve coatings that are hard up to 2000 HV and over 20 µm thick with good tribological properties.
The Fraunhofer Institute IWU
The Fraunhofer Institute for Machine Tools and Forming Technology IWU (www.iwu.fraunhofer.de) is a driving force for innovations in the field of production technology research and development. With around 600 employees at the Chemnitz, Dresden and Zittau sites, it develops potential for competitive manufacturing. The focus of science and contract research is on components, procedures and processes as well as the associated complex machine systems, practically the entire factory. The following scientific fields are being worked on:
- Mechatronics and functional lightweight construction
- Machine tools, production systems and machining technology
- Forming technology
The laboratory tour provided information about the various activities of the Fraunhofer IWU
As the leading institute for resource-efficient production, the focus is on the development of efficiency technologies and intelligent production systems for the manufacture of car body and powertrain components as well as the optimization of the associated forming and machining production processes. The development of lightweight structures and technologies for processing new materials, as well as the transfer of functions in assemblies, are important success factors here.
Advancing digitalization is a key topic for the future of our time. The institute is developing holistic solutions with concrete added value that will continue to strengthen and expand the competitive position of its partners in the future. The foundation for this is the "E3 Research Factory for Resource-Efficient Production". Together with research and industry partners, solutions for efficient technologies as well as factory planning concepts for flexible, resource-efficient production and innovative information and visualization technologies for the integration of people as guarantors of success in the factory of the future are being developed.
