Analyzing wear mechanisms and developments of surface layers in WC/Co-cemented carbide cutting inserts is of great importance for metal-cutting manufacturing. By knowing relevant processes within the surface layers of cutting tools during machining the choice of machining parameters can be influenced to get less wear and high tool life of the cutting tool. Tool wear obviously influences tool life and surface integrity of the workpiece (residual stresses, surface quality, work hardening, etc.), so the choice of optimised process parameters is of great relevance. Vapour-deposited coatings on WC/Co-cemented carbide cutting inserts are known to improve machining performance and tool life, but the mechanisms behind these improvements are not fully understood. The interaction between commercial TiN-coated and uncoated WC/Co-cemented carbide cutting inserts and a normalised SAE 1045 steel workpiece was investigated during a dry plain turning operation with constant material removal under varied machining parameters. Tool wear was assessed by light-optical microscopy, scanning electron microscopy (SEM), and EDX analysis. The state of surface layer was investigated by metallographic sectioning. Microstructural changes and material transfer due to tribological processes in the cutting zone were examined by SEM and EDX analyses. 1. Introduction At machining metals it is important to know about the wear behaviour of the cutting tool. This importance arises due to the fact that the surface integrity of the machined workpiece is influenced by tool wear [1, 2]. In this case surface integrity is described by three main parameters: the surface roughness, the residual stress state, and the work hardening in the surface zone [1]. For further improvement in the knowledge of wear behaviour of cutting tools the surface layer states of the worn tools are important to distinguish between different wear mechanisms acting in the cutting zone. One possibility at investigating wear with respect to the applied cutting parameters (e.g., cutting speed, feed rate, and depth of cut) is the idea proposed by Lim and Ashby with the wear mechanism maps [3]. Here the most important aspects of wear (seizure, delamination wear, mild wear, severe wear, etc.) are displayed with respect to the parameters varied in the wear tests (sliding velocity, pressure, etc.). The wear map approach is also applied to metal machining, and therefore the wear is displayed as a function of cutting speed and feed rate [4, 5]. In this work the aim is to develop a better understanding of the wear characteristics
References
[1]
I. S. Jawahir, E. Brinksmeier, R. M’Saoubi et al., “Surface integrity in material removal processes: recent advances,” CIRP Annals—Manufacturing Technology, vol. 60, no. 2, pp. 603–626, 2011.
[2]
Q. Xie, A. E. Bayoumi, and L. A. Kendall, “On tool wear and its effect on machined surface integrity,” Journal of Materials Shaping Technology, vol. 8, no. 4, pp. 255–265, 1990.
[3]
S. C. Lim and M. F. Ashby, “Wear-mechanism maps,” Acta Metallurgica, vol. 35, no. 1, pp. 1–24, 1987.
[4]
S. C. Lim, Y. B. Liu, S. H. Lee, and K. H. W. Seah, “Mapping the wear of some cutting-tool materials,” Wear, vol. 162-164, pp. 971–974, 1993.
[5]
S. C. Lim, “Recent developments in wear-mechanism maps,” Tribology International, vol. 31, no. 1–3, pp. 87–97, 1998.
[6]
S. Karag？z and H. F. Fischmeister, “Metallographic observations on the wear process of TiN-coated cutting tools,” Surface and Coatings Technology, vol. 81, no. 2-3, pp. 190–200, 1996.
[7]
“ISO 3685: tool-life testing with single-point turning tools,” 1993.
[8]
V. P. Astakhov, Tribology of Metal Cutting, vol. 52 of Tribology and Interface Engineering Series, Elsevier, 2006.
[9]
V. P. Astakhov, “The assessment of cutting tool wear,” International Journal of Machine Tools and Manufacture, vol. 44, no. 6, pp. 637–647, 2004.
[10]
S. Jacobson and P. Wallén, “A new classification system for dead zones in metal cutting,” International Journal of Machine Tool Design and Research, vol. 28, no. 4, pp. 529–538, 1988.
[11]
P. K. Philip, “Built-up edge phenomenon in machining steel with carbide,” International Journal of Machine Tool Design and Research, vol. 11, no. 2, pp. 121–132, 1971.
[12]
H. Opitz and M. Gappisch, “Some recent research on the wear behaviour of carbide cutting tools,” International Journal of Machine Tool Design and Research, vol. 2, no. 1, pp. 43–73, 1962.
[13]
J. A. Arsecularatne, L. C. Zhang, and C. Montross, “Wear and tool life of tungsten carbide, PCBN and PCD cutting tools,” International Journal of Machine Tools and Manufacture, vol. 46, no. 5, pp. 482–491, 2006.
[14]
H. O. Gekonde and S. V. Subramanian, “Tribology of tool-chip interface and tool wear mechanisms,” Surface and Coatings Technology, vol. 149, no. 2-3, pp. 151–160, 2002.
[15]
“Oerlikon Balzers product information BALINIT A,” 2011.
[16]
“Springer Materials: the Landolt B？rnstein database, the worlds largest resource for physical and chemical data,” 2009.
[17]
Valentin L. Popov, Kontaktmechanik und Reibung: Von der Nanotribologie bis zur Erdbebendynamik, Springer, Berlin, Germany, 2010.
[18]
J. Gerth, M. Larsson, U. Wiklund, F. Riddar, and S. Hogmark, “On the wear of PVD-coated HSS hobs in dry gear cutting,” Wear, vol. 266, no. 3-4, pp. 444–452, 2009.
