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3743 |
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Wednesday, May 21, 2014, Hall H3 11:50 AM Properties Characterization & Testing Methods |
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Characterization of a HVOF-sprayed WC-CoCr coating before and after laser-assisted turning |
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Lidong Zhao* / RWTH Aachen University, Germany Kirsten Bobzin / Surface Engineering Institute, RWTH Aachen University, Germany Thomas Frederik Linke/ Surface Engineering Institute, RWTH Aachen University, Germany Mehmet Öte/ Surface Engineering Institute, RWTH Aachen University, Germany Fritz Klocke/ Fraunhofer Institute for Production Technology IPT, Germany Christoph Brummer/ Fraunhofer Institute for Production Technology IPT, Germany Stefan Graefe/ Fraunhofer Institute for Production Technology IPT, Germany |
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HVOF sprayed WC-Co coatings are widely used as high quality protective coatings against wear and corrosion. For applications such as hard chrome replacements, the as-sprayed WC Co coatings do not meet the requirements of surface quality and thus must be finished. Today, they are almost only ground and polished using diamond tools instead of being turned or milled due to high wear rates of turning and milling tools and due to the lower qualities of the turned or milled surfaces compared to grinding and polishing. A new turning process laser-assisted turning has recently been developed and successfully applied to finish Si3N4 ceramics. This process can also be a promising alternative to grinding of WC Co coatings, because the cutting resistance of the WC-Co coatings can be significantly reduced thanks to enhanced local surface temperatures by laser heating compared to conventional turning, thus leading to improved surface qualities, reduced wear of turning tools and improved finishing efficiency. In this study, a WC-CoCr coating is produced using a HVOF spray system K2 (GTV, Luckenbach, Germany). The as-sprayed coating is characterized in terms of its surface morphology, microstructure, phase composition, hardness and wear resistance. In the next step, the coating is turned with the aid of laser heating using different parameters. The influence of parameters on the surface quality is investigated. Finally, the turned coating is again characterized concerning the above mentioned aspects. In this way, the feasibility of laser-assisted turning of WC-Co coatings is evaluated. |