TiB₂ particle reinforced high-stiffness steel is one of the composite materials that aim to improve Young’s modulus by compositing TiB₂ particles into a stainless steel base phase. This material is designed to exhibit higher rigidity and strength than conventional iron-based materials by using TiB₂ particles as the reinforcing phase, and is expected to reduce the weight of high-load components in engines. For this reason, tool life is very short when machining this material. Therefore, high Young’s modulus steel containing TiB₂ particles is known to be one of the most difficult-to-cut materials. The purpose of this study was to investigate how to extend tool life in the milling of high-Young’s-modulus steel. Cutting speed dependence of tool life was investigated by end milling using a binderless CBN tool with excellent hardness and bending strength. In addition, the tool damage mechanism was also investigated. The results showed that tools composed of binderless CBN tool have a longer life than conventional CBN tool. In this type of binderless CBN tool, the tool wear rate tended to increase with increasing cutting speed. In addition, the longest tool life was obtained at a cutting speed of 1.25 m/s, though wear rate increased at a boundary cutting length of 1300 m. The wear rate was found to increase with increasing cutting speed. Temperature measurement results indicate that the primary cause of tool damage was mechanical wear, as the temperatures were much too low for a reaction between cBN and Fe. Friction tests revealed scratch marks on the tool originating from crushed cBN particles produced by the crushing of the cutting edge. This indicates that wear is accelerated by the high frictional energy of the cBN powder rubbing against the flank face.

1. [1] W. Zhang and J. Xu, “Advanced lightweight materials for Automobiles: A review,” Materials & Design, Vol.221, Article No.110994, 2022. https://doi.org/10.1016/j.matdes.2022.110994
2. [2] Y. Daijyo, “Present and Future Technologies for Automobiles Resolving Problems Associated with Environment and Energy,” NTN Technical Review, Vol.70, pp. 2-7, 2002 (in Japanese).
3. [3] H. Fujii and M. Saga, “Non-Ferrous Structural Materials (Titanium, Aluminum),” Nippon Steel Technical Report, No.101, pp. 171-176, 2012.
4. [4] T. Saito, “Affordable High-performance Ti/TiB Metal Matrix Composites Tailored for Automobile Engine Components: Materials Design, Manufacturing Process, and Remaining Issues,” R&D Review of Toyota CRDL, Vol.51, No.1, pp. 1-30, 2020.
5. [5] K. Tanaka and T. Saito, “Phase Equilibria in TiB₂-Reinforced High Modulus Steel,” J.of Phase Equilibria, Vol.20, No.3, pp. 207-214, 1999. https://doi.org/10.1361/105497199770335730
6. [6] K. Tanaka, T. Ohshima, and T. Saito, “Mechanical properties and hot workability of TiB₂-particle reinforced high stiffness steel,” Iron and Steel, Vol.84, No.10, pp. 747-754, 1998 (in Japanese). https://doi.org/10.2355/tetsutohagane1955.84.10_747
7. [7] K. Nishino, H. Kawaura, H. Tanaka, T. Horie, T. Saito, and H. Uchida, “High performance alloys for turbochargers,” Toyota Central R&D Labs R&D Review, Vol.35, No.3, pp. 27-34, 2000 (in Japanese).
8. [8] A. Manna and B. Bhattacharayya, “A Study on Machinability of Al/SiC-MMC,” J. of Materials Processing Technology, Vol.140, Issues 1-3, pp. 711-716, 2003. https://doi.org/10.1016/S0924-0136(03)00905-1
9. [9] T. Hasegawa, T. Miura, and N. Nishikwaki, “Relation between wear of sintered tools and particle hardness in tools and work materials during cutting of particle strengthened aluminum composites,” J. of Japan Institute of Light Metals, Vol.44, No.10, pp. 543-548, 1994 (in Japanese). https://doi.org/10.2464/jilm.44.543
10. [10] I. Çiftci, M. Turker, and U. Şeker, “CBN cutting tool wear during machining of particulate reinforced MMCs,” Wear, Vol.257, Issues 9-10, pp. 1041-1046, 2004. https://doi.org/10.1016/j.wear.2004.07.005
11. [11] X. Ding, W. Y. H. Liew, and X. D. Liu, “Evaluation of machining performance of MMC with PCBN and PCD tools,” Wear, Vol.259, Issues 7-12, pp. 1225-1234, 2005. https://doi.org/10.1016/j.wear.2005.02.094
12. [12] C. J. E. Andrewes, H.-Y. Feng, and W. M. Lau, “Machining of an aluminum/SiC composite using diamond inserts,” J. of Materials Processing Technology, Vol.102, Issues 1-3, pp. 25-29, 2000. https://doi.org/10.1016/S0924-0136(00)00425-8
13. [13] H. Sumiya, Y. Ishida, K. Arimoto, and K. Harano, “Real indentation hardness of nano-polycrystalline cBN synthesized by direct conversion sintering under HPHT,” Diamond and Related Materials, Vol.48, pp. 47-51, 2014. https://doi.org/10.1016/j.diamond.2014.06.009
14. [14] H. Sumiya and K. Harano, “Wear Characteristics of Binder-Less Nano-Polycrystalline Diamond and Cubic Boron Nitride,” Advanced Materials Reserch, Vol.1017, pp. 406-410, 2014. https://doi.org/10.4028/www.scientific.net/AMR.1017.406
15. [15] H. Kato, K. Shintani, and H. Sumiya, “Cutting performance of a binder-less sintered cubic boron nitride tool in the high-speed milling of gray cast iron,” J. of Materials Processing Technology, Vol.127, Issue 2, pp. 217-221, 2002. https://doi.org/10.1016/S0924-0136(02)00145-0
16. [16] K. Hamaguchi, H. Kodama, and K. Okuda, “Tool Wear and Surface Roughness in Milling of Die Steel Using Binderless CBN End Mill,” Int. J. Automation Technol., Vol.11, No.1, pp. 84-89, 2017. https://doi.org/10.20965/ijat.2017.p0084
17. [17] D. Suzuki, F. Itoigawa, K. Kawata, and T. Nakamura, “Using Pulse Laser Processing to Shape Cutting Edge of PcBN Tool for High-Precision Turning of Hardened Steel,” Int. J. Automation Technol., Vol.7, No.3, pp. 337-344, 2013. https://doi.org/10.20965/ijat.2013.p0337
18. [18] J. Polte, M. Polte, D. Lorenz, D. Oberschmidt, H. Sturm, and E. Uhlmann, “Binderless-cBN as Cutting Material for Ultra-Precision Machining of Stainless Steel,” Advanced Materials Research, Vol.1018, pp. 107-114, 2014. https://doi.org/10.4028/www.scientific.net/AMR.1018.107
19. [19] Z. G. Wang, M. Rahman, and Y. S. Wong, “Tool wear characteristics of binderless CBN tools used in high-speed milling of titanium alloys,” Wear, Vol.258, Issues 5-6, pp. 752-758, 2005. https://doi.org/10.1016/j.wear.2004.09.066
20. [20] K. Shintani, H. Kato, K. Kanada, I. Iguchi, and Y, Ito, “Study on cutting of TiB₂ particle composite high stiffness steel,” J. of Japan Society for Precision Engineering, Vol.79, No.4, pp. 368-372, 2013 (in Japanese). https://doi.org/10.2493/jjspe.79.368
21. [21] H. Sumiya, S. Uesaka, and S. Satoh, “Mechanical properties of high purity polycrystalline cBN synthesized by direct conversion sintering method,” J. Materials Science, Vol.35, pp. 1181-1186, 2000. https://doi.org/10.1023/A:1004780218732
22. [22] H. Sumiya and S. Uesaka, “Microstructure and Properties of High-purity Polycrystalline cBN,” J. of the Japan Society of Powder and Powder Metallurgy, Vol.49, No.4, pp. 327-332, 2002 (in Japanese). https://doi.org/10.2497/jjspm.49.327
23. [23] K. Hirosaki, K. Shintani, H. Kato, F. Asakura, and K. Matsuo, “High Speed Machining of Bio-Titanuium Alloy with a Binder-Less PcBN Tool,” JSME Int. J., Series C, Vol.47, No.1, pp. 14-20, 2004. https://doi.org/10.1299/jsmec.47.14
24. [24] T. Hosono, H. Hidai, and K. Tokura, “Reactivity of high temperature metals with cBN,” J. of Japan Society for Precision Engineering, Vol.70, Issue 10, pp. 1271-1275, 2004 (in Japanese). https://doi.org/10.2493/jspe.70.1271