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5449 |
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Wednesday, June 07, 2017, Hall Y 4:10 PM Session Young Professionals |
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Cold gas spraying of lead-free bearing bronzes |
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Stephan Theimer* / Helmut-Schmidt-University of the Federal Armed Forces, Germany Brethack Patrick / Department of Mechanical Engineering, Helmut Schmidt University, University of the Federal Armed Forces Hamburg, Hamburg, Germany, Germany Frank Gärtner/ Department of Mechanical Engineering, Helmut Schmidt University, University of the Federal Armed Forces Hamburg, Germany Thomas Klassen/ Department of Mechanical Engineering, Helmut Schmidt University, University of the Federal Armed Forces Hamburg, Germany |
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In current process techniques to manufacture sliding bearings, bronze components are soldered to the respective parts, which is cost and energy intensive. Apart from that, so far most bearing materials still contain lead, which in new applications has to be omitted by EU laws to avoid associated health risks. The present study aims to offer solutions for both by using cold gas spraying as additive manufacturing technique for processing bearings directly onto steel parts and by applying that to new lead-free bronze alloys. Two different lead-free bronze alloys were processed as powders by gas atomization to meet the definition for cold spraying. For some of the alloys, super-saturated solid solution of alpha phase and refined microstructure by rapid solidification during powder atomization result in up to more than two times higher strength and lower plasticity as compared to cast material. Cold gas spraying was applied by varying the process gas pressures, process gas temperatures, as well as spray distance, with the aim to study influences by impact conditions and effective surface temperature on particle deformation and bonding. The results show that attainable coating qualities highly differ for the two bronzes. For the softer powders, cold-sprayed coating qualities can be improved by enhancing impact conditions, and tuning of surface temperatures by substrate heating. Respective coatings show low porosity, high hardness and high mechanical strength, and in consequence good cavitation resistance, similar to properties of bulk cast material. In addition, good bond strength is achieved, so that respectively manufactured parts meet the requirements for new bearing applications. |