Surface welding of duplex stainless steel on lamellar grey cast iron was performed to produce thick (several millimetres) protective surface layers with a regulated gas metal arc welding process. As dominant parameters, the influence of the composition of the shielding gas (argon-helium mixture) as well as preheating temperature on the corrosion resistance were investigated. Both the addition of helium to shielding gas and preheating of the base material increase the heat input and reduce the cooling rates and result in higher dilution. This leads to reduced hardness in the heat affected zone and prevents cracking. However, the formation and portion of carbides in the surface layers increase. The influence of these parameters on the microstructure in the surface layers as well as in the heat affected zone and the influence on the corrosion behaviour in artificial seawater were investigated with immersion tests and potentiodynamic polarization measurements. The corrosion properties of the parent lamellar grey cast iron were greatly enhanced by the surface layers, but inferior to duplex stainless steel. With additional metallographic investigations the corrosion mechanisms were investigated. The corrosion mechanisms are extensively influenced by the phase distribution in the surface layers and by the formation of carbides.Keywords: Grey cast iron / surface welding / regulated gas metal arc welding process / microstructure / corrosion Corresponding author: B. Heider, Zentrum fü r Konstruktionswerkstoffe (MPA-IfW Darmstadt), TU Darmstadt,

Aufgrund der ausgezeichneten Gießbarkeit und Bearbeitbarkeit, der guten mechanischen Eigenschaften sowie der wirtschaftlichen Vorteile werden Graugusswerkstoffe sehr verbreitet zur Herstellung von Bauteilen in rotierenden Maschinen, wie z. B. in Pumpen verwendet. Jedoch müssen sie oft durch wesentlich teurere Werkstoffe mit einem zusätzlich aufwendigeren Fertigungsprozess ersetzt werden, um erhöhten Anforderungen an die Beanspruchbarkeit z. B. in Form von Korrosions‐ und Erosionsbeständigkeit von Bauteilen gerecht zu werden. Ein potenzieller wirtschaftlicherer Lösungsweg zur Erhöhung der Korrosions‐ und Erosionsbeständigkeit von Gussbauteilen liegt darin, Gussbauteile mit einer Korrosions‐ und Erosionsschutzschicht zu versehen. Im Rahmen dieser Untersuchungen wurde ein neuartiges eisenbasiertes Beschichtungssystem auf Basis von einer FeCrMnBC‐Legierung entwickelt. Diese FeCrMnBC‐Legierung stellt im Vergleich zu hochlegierten Stählen oder Nickel‐ und Kobaltbasislegierungen eine wirtschaftlich interessante Alternative dar. Die FeCrMnBC‐Legierung wurde mit dem Atmosphärischen Plasmaspritzen aufgetragen und im Hinblick auf ihr Korrosionsverhalten untersucht. Gegenüber dem unbeschichteten Gusswerkstoff (EN‐GJL‐250) wird eine signifikante Verbesserung der Korrosions‐ und Erosionsbeständigkeit erreicht. Diese neuartige Beschichtung weist damit ein großes Potenzial zum lokalen Schutz vor Korrosion und Erosion von Gussbauteilen auf.

Vermiculargusswerkstoffe zählen zu vergleichsweise schwer zerspanbaren Werkstoffen im automobilen Antriebsstrang. Insbesondere kontinuierliche Schnittbedingungen stellen hohe Anforderungen an die eingesetzten Schneidstoffe. Kryogene Kühlverfahren können einen entscheidenden Beitrag zur Verlängerung der Werkzeugstandzeit von Hartmetall- und diamantbasierten Schneidstoffen leisten. Der Fachbeitrag fasst die Untersuchungen zum Einfluss der Prozesskühlung auf die Werkstoff- und Spanbildungseigenschaften zusammen.   Compacted graphite iron (CGI-450) with its excellent mechanical properties has a large and still increasing importance in the field of construction materials, especially in the field of automotive powertrain applications. The choice of tungsten carbide and diamond-based cutting tools with suitable technological constraints and different cooling strategies in view of chip formation, chip shape and cutting energy are to be illustrated in the following tests.

Fe-based coatings, such as novel FeCrMnBC alloys, have both economic and ecological advantages compared to other coatings like Ni-based or Co-based coatings. In recent years, high performance Fe-based wear and corrosion resistant coating systems have been developed. Some of them have even been introduced into the market. However, the suitability of the FeCrMnBC alloy as coating for cast iron under complex erosive and corrosive stresses in particle-loaded fluids for pump parts has not been investigated yet. Especially the impact of the process robustness of three-cathode plasma spraying coatings applied with variable process parameters like stand-off distance and spray angle is in the focus of interest. The objective of the present work has been the characterization of novel FeCrMnBC alloys, for the first time deposited via Thermal Spray processes. The corrosion resistances as well as the cavitation and erosion properties were separately evaluated by current density-potential measurements and supersonic cavitation in artificial sea water. Erosion corrosion behavior has been investigated in a pump test rig with 10 wt.-% corundum (Al2O3) particles. The results show that the reduction of spray angle and the variation of stand-off distance limit the corrosion and cavitation resistance in different ways. The erosion behavior shows only small variations for the tested parameters. The results reveal that the FeCrMnBC coatings exhibit high process robustness for the chosen parameter variations and a large potential to improve the protection of cast iron even for not optimized conditions.

Three-cathode plasma spraying is characterized by high process robustness in terms of particle in-flight properties due to high stability of plasma jet. However, during coating parts with complex geometries, process parameters such as stand-off distance and spray angle usually cannot be kept at optimized conditions. In this study, the process robustness during three-cathode plasma spraying of a novel FeCrMnBC alloy was investigated by varying stand-off distance and spray angle to simulate spray conditions for complex geometries. A three-cathode plasma generator TriplexProTM-210 was used to spray FeCrMnBC powder with a fraction of -45 +20 µm onto substrates of cast iron EN-GJL-250. The stand-off distance and the spray angle were varied from d=90 mm to d=110 mm and between ø=90° and ø=60°, respectively, while the other process parameters were kept constant. The results revealed that the reduction of spray angle caused an about 15 % decrease of coating thickness, about 40 % porosity increase and about 15% increase of bond strength. In contrast, the variation of stand-off distance changed only insignificantly the coating thickness, porosity and bond strength. The variation of stand-off distance and spray angle did not result in significant changes in the coating microhardness. The reduction of spray angle resulted in significant worsening of the corrosion protection ability of the coating system.