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Schilde, Belgium

Woydt M.,BAM Federal Institute of Materials Research and Testing | Mohrbacher H.,Niobelcon BVBA
Ceramic Engineering and Science Proceedings | Year: 2016

The tribological behavior under dry sliding of a Fe3Al-NbC composite prepared by pyrometallurgical synthesis is compared to NbC-based hard metals bonded by cobalt or Fe3A1. The dry sliding wear resistance (0, 1-7/10 m/s) of the present Fe3Al-NbC with ∼60% NbC was close to those known of NbC-based hard metals. No grain pull-outs or fragmentations of the NbC grains were seen in the wear tracks, as a metallurgical interphase was formed between matrix and NbC grains. Source


Spottl M.,WISCO Lasertechnik GmbH | Mohrbacher H.,Niobelcon BVBA
Advances in Manufacturing | Year: 2014

Laser welding is an established manufacturing technology for a large variety of automotive applications due to its attractive properties such as low heat input, high precision and fast welding speed. Especially when welding high strength steels, which are dominantly used in today’s car body construction, the low heat input by laser welding bears significant advantages with regard to the properties of the weld seam. The exploitation of the full application potential of laser welding in mass production requires an appropriate manufacturing concept and corresponding auxiliary technologies. The present paper demonstrates the integration of laser welding into the surrounding manufacturing concepts by a modular setup with different levels of automation. This approach offers flexible solutions for individual needs thereby optimizing investment cost, labor cost and productivity. Recently available laser sources enable exceptionally high welding speed on thin gauged sheet metals but require efficient material handling concepts to utilize the full speed potential. Industrial concepts are presented offering efficient material handling and high process robustness for mass production welding. © 2014 Shanghai University and Springer-Verlag Berlin Heidelberg. Source


Mohrbacher H.,Niobelcon BVBA
Energy Materials 2014, Conference Proceedings | Year: 2014

Seamless pipes are available with wall gages of up to 100 mm and outer diameters up to around 700 mm. Such pipes are typically used for oil country tubular goods as well as for structural applications. Due to market requirements the demand for high strength grade seamless pipes is increasing. Many applications need high toughness in addition to high strength. The different rolling processes applied in production depend on wall gage and pipe diameter. The continuous mandrel mill process is used to produce smaller gages and diameters; plug mill processing covers medium gages and diameters; Pilger mill processing allows producing larger diameters and heavy wall gage. In all these processes only a limited degree of thermo-mechanical rolling can be achieved. Therefore strengthening and toughening by severe grain refinement employing a conventional niobium-based microalloying concept is not easily achievable. Accordingly, high strength and toughness seamless pipe is typically produced via a quench and tempering process route. This route however is costly and above that often constitutes a capacity bottleneck in the mill. Innovative low-carbon alloy concepts however do allow producing strength up to grade X70 at very high toughness directly off the rolling plant, i.e., without quench and tempering treatment. Due to the low carbon content also welding is much facilitated. The paper reveals the metallurgical principles, which are based on appropriate niobium and molybdenum alloying. Additionally the paper demonstrates how heavy gaged seamless pipes up to 70 mm wall thickness can be produced based on a low-carbon Nb-Mo approach using quench and temper treatment. Source


Woydt M.,BAM Federal Institute of Materials Research and Testing | Mohrbacher H.,Niobelcon BVBA
International Journal of Refractory Metals and Hard Materials | Year: 2015

The tribological profile of alumina (99.7%) mated against rotating disks made in binder-less niobium carbide (NbC) and cobalt-bonded NbC were determined under unidirectional sliding tests (0.1 m/s to 8.0 m/s; 22 °C and 400 °C) as well as in oscillation tests (f=20 Hz, Δx=0.2 mm, 2/50/98% rel. humidity, n=105/106 cycles) under unlubricated (dry) conditions. In addition, themicrostructure andmechanical properties of binderless NbC and NbC bonded with 8% cobalt were determined as well. The reason for testing hot-pressed NbC was to avoid side effects generated by sintering additives and/or second phases. The tribological data obtained were benchmarked with different ceramics, cermets and thermally sprayed coatings. NbC and cobalt-bonded NbC exhibited low wear rates under dry sliding associated with high load carrying capacity. The tribological profile established revealed a strong position of NbC bearing materials under tribological considerations and for closed tribo-systems against traditional references, such as WC, Cr3C2 and (Ti,Mo)(C,N). © 2014 Elsevier Ltd. Source


Mohrbacher H.,Niobelcon BVBA | Zhai Q.,Shanghai University
Materials Science and Technology Conference and Exhibition 2011, MS and T'11 | Year: 2011

Niobium when alloyed to hypo- as well as hypereutectic iron has several beneficial metallurgical effects. It refines the eutectic cell size, graphite structure and also the lamellae spacing of the pearlite matrix. Nb affects the nucleation of graphite and can hence support inoculation. It also narrows down the temperature hysteresis between austenite and pearlite formation, which is important to cyclic heating. Finally, the ultra hard NbC particles formed lead to a markedly increased wear resistance of the material. The paper elucidates how these effects of Nb can be used to make brake discs with better properties and demonstrates processing benefits in the production of cast iron. Finally some examples of application in heavy trucks and recent passenger cars are given. Copyright © 2011 MS&T'11®. Source

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