Investigations on temperature-activated coatings for friction reduction during turning of titanium alloys
Metal-Cutting and Abrasive Manufacturing Engineering
Final Report Abstract
The titanium alloy TiAl6V4 is an attractive lightweight material due to its material properties and is established in the market. It is used in various applications, including aerospace, medical technology, and the automotive industry. Compared to steel materials, TiAl6V4 has a low elastic modulus, high yield strength, low thermal conductivity, and a pronounced tendency for cold work hardening. As a result, the alloy is classified as difficult to machine. The heat generated during the machining process is only partially dissipated through the chip and mostly remains in the tool. Additionally, adhesion to chip and clearance surfaces increases, altering cutting geometry and intensifying tool wear. Due to the relatively low Young’s modulus with high yield strength of titanium, a springback effect occurs at the free surface, which reduces the effective clearance angle. As a result, additional self-excited vibrations are induced in addition to the vibrations caused by the lamellar chip formation. One way to reduce tool damage and increase productivity during machining of TiAl6V4 is to use physical vapor deposition (PVD) hard coatings. Within the scope of the research project, triboactive coatings were developed whose mode of operation is based on the formation of easily shearable oxide phases. These are intended to minimize thermal and mechanical stresses during the machining of titanium alloys. Numerous analyses were carried out to understand the application behavior of the triboactive coatings in contact with TiAl6V4 under various conditions. One focus was the analysis of the thermal and mechanical loading in the machining process. This included the investigation of temperature development, cutting and friction forces as well as the wear behavior of the tools. Through these investigations, it was found that in addition to strong adhesion, crater wear and plastic cutting edge deformation also affect tool wear. Another focus was the investigation of the oxidation and diffusion behavior of the coating. Here, the formation of friction-reducing oxide phases was demonstrated despite the use of cooling lubricant. In addition, diffusion of metallic coating components into the TiAl6V4 chip can be ruled out. The results obtained offer the possibility of exploiting the potential for increasing productivity and improving the quality of the machined workpieces, particularly in finishing processes, through the targeted further development of the coatings investigated. This research project thus represents an important step towards more efficient and environmentally friendly processes in the economic machining of titanium alloys.
Publications
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Development of a Process-Oriented Tribological Test Rig for the Performance Assessment of Tool Coatings in Turning of Titanium Ti6Al4V. SSRN Electronic Journal.
Hintze, Wolfgang; Ploog, Petter; Bluehm, Melchior & Möller, Carsten
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Functional PVD Hard Coatings for High Temperature Cutting Processes. Lecture Notes in Production Engineering, 266-274. Springer Berlin Heidelberg.
Stachowski, N.; Kruppe, N. C.; Brögelmann, T. & Bobzin, K.
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Self-Lubricating PVD Hard Coatings through Tribological Activation. Defect and Diffusion Forum, 404, 109-116.
Bobzin, Kirsten; Brögelmann, Tobias; Kruppe, Nathan Christopher & Stachowski, Nina
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Oxidation and Diffusion Behavior of CrAlVN Hard Coatings for Machining Ti6Al4V. Lecture Notes in Production Engineering, 212-220. Springer International Publishing.
Stachowski, N.; Carlet, M.; Kalscheuer, C. & Bobzin, K.
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Self‐lubricating CrAlVN coatings for turning of Ti6Al4V: oxidation and wear behavior. Materialwissenschaft und Werkstofftechnik, 52(12), 1394-1412.
Bobzin, K.; Brögelmann, T.; Stachowski, N.; Hintze, W.; Möller, C. & Ploog, P.
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Wear development of self-lubricating CrAlVN coatings during turning Ti6Al4V, (December 1, 2021), Proceedings of the Machining Innovations Conference (MIC) 2021
K. Bobzin; C. Kalscheuer; M. Carlet; N. Stachowski; W. Hintze; C. Möller & P. Ploog
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Influence of self-lubricating tool coatings on cutting temperature and coefficient of friction during turning of Ti6Al4V, Proceedings of the 19th Plansee Seminar, International Conference on Refractory Metals and Hard Materials May 30 – June 3 (2022)
W. Hintze; C. Möller; P. Ploog; K. Bobzin; C. Kalscheuer; M. Carlet & N. Stachowski
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Self-lubricating CrAlMoN high performance tool coatings for machining of TiAl6V4. Production Engineering, 17(3-4), 437-444.
Bobzin, K.; Kalscheuer, C.; Carlet, M.; Stachowski, N.; Hintze, W.; Möller, C. & Ploog, P.
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Oxidation and wear behavior of CrAlMoN with varied Mo-content for cutting Ti6Al4V. Production Engineering, 18(1), 87–97.
Bobzin, K.; Kalscheuer, C.; Stachowski, N.; Dege, J.; Hintze, W.; Möller, C. & Ploog, P.
