PVD-coating of electroplated cBN grinding tools to optimize the wear and application behavior when grinding nickel-based alloys
Final Report Abstract
The overall objective of the research project was to develop physical vapor deposition (PVD) coatings for electroplated cBN grinding wheels. The use of the coating was intended to reduce wear and friction processes in the machining of nickel-based alloys. Another objective was to increase the chip space by reducing the grain embedding depth. The coating was intended to compensate for any resulting disadvantages in grain stability. The results showed that the TiN, AlTiN, AlTiSiN and TiB2 coatings formed good coating adhesion on the abrasive body for almost all the coating parameters investigated. The overall adhesion on the nickel bond was more pronounced than on the abrasive grain. To investigate the grain retention forces, specimens with grain embedment depths of 45 %, 55 % and 70 % (industrial standard) of the average grain diameter were obtained from the manufacturer. No significant differences in the grain retention forces were observed. On average, a slight increase in the grain retention force was observed for all specimens as a result of the coating. The AlTiN and TiB2 coatings were then selected for the grinding tests. The selection was based on the coating tests and other coating properties, such as hardness, oxidation resistance, thermal barrier effect and friction properties. In tribology tests, 43% lower friction coefficients were demonstrated for TiB2 using cooling lubricant than for AlTiN. This was attributed to the low surface roughness and possible formation of friction-reducing compounds at higher temperatures. In the grinding tests, uncoated and coated grinding wheels with a grain embedment depth of 70 % (reference) and 50 % were used. The AlTiN and TiB2 coating were applied to grinding wheels with 50% grain embedment depth. As a result, the reduced grain embedment depth of the uncoated grinding wheels already reduced the process forces by 25%. In the case of the coating systems, only the use of TiB2 further reduced the process forces by up to 18%. Compared to the uncoated grinding wheel, the coated grinding wheels led to a higher peripheral zone influence, which is attributed to the thermal barrier effect of the coatings. However, at higher cutting volumes, less peripheral zone influence was observed with TiB2 indicating a lower thermo-mechanical stress. The coating only leads to minor additional tool costs, which are in the range of 4% of the total costs. Regarding the possibility of reducing tool changes, tool optimization by means of coating thus offers high potential for an economic application. In future investigations, further studies on tool life under different process conditions should be carried out. In addition, the transferability to other workpiece materials should be investigated.
Publications
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Neue Potenziale für die Schleif-bearbeitung von Superlegierungen. ZWF Zeitschrift für wirtschaftlichen Fabrikbetrieb, 115(10), 723-726.
Hartig, Jörg; Kirsch, Benjamin & Aurich, Jan C.
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PVD-Hartstoffschichten für Schleifwerkzeuge zum Bearbeiten von Superlegierungen/Wear resistant PVD coatings for cBN grinding tools. wt Werkstattstechnik online, 111(06), 419-429.
Hartig, Jörg; Kirsch, Benjamin & Aurich, Jan C.
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Entwicklung von PVD-Schutzschichten zur Leistungssteigerung galvanisch gebundener Hochleistungsschleifscheiben. Jahrbuch Schleifen, Honen, Läppen und Polieren - Verfahren und Maschinen 70 (2022): S. 148-165.
J. Hartig, B. Kirsch, S. Diederichs, E. Kerscher & J.C. Aurich
