OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 7 No. 2 2025 capable of providing productivity intensification [2]. Modern ceramic cutting tools are made in the form of ceramics based on aluminium oxide, zirconium dioxide, cermets, silicon nitride and carbide, SiAlON, and others [2]. The martensitic transformation from a metastable tetragonal phase to a stable monoclinic phase creates a stress field around propagating cracks, which is critical to the phenomenon of increasing the fracture toughness of zirconium dioxide ceramics due to phase transformation [3, 4]. Alloying impurities such as Y2O3 are commonly added to stabilize the high-temperature tetragonal and/or cubic phase in the microstructure of sintered ceramics [3, 5]. Despite its excellent mechanical properties, the applicability of tetragonal polycrystalline zirconium dioxide (Y-TZP) for wear-resistant applications is limited due to its low hardness [5]. However, for example, micro-sized end mills made of Y-TZP ceramics have shown the best results among ceramic materials in terms of tool cutting edge sharpness. It is worth noting the reported increase in wear resistance in micro-milling tests using Y-TZP tools [6], in which the dimensional effects of cutting edge microgeometry, such as the ratio of the uncut chip thickness to the radius of cutting edge rounding, are known to lead to high mechanical stresses [6]. Ceramic composites with a high hardness using an aluminium oxide matrix with zirconium dioxide inclusions increasing its fracture toughness (ZTA) are widely used as ceramic cutting tools for machining hard and wear-resistant materials [2, 7‑16]. In [12], high-performance ceramic cutting tools of complex shaped ZTA were designed with a chipbreaker and were investigated for the first time. The investigated samples were fabricated using 3D printing based on bath photopolymerisation combined with a hot isostatic sintering process. Cutting tools with a relative density of 99.34 %, a Vickers hardness of 17.98 ± 0.20 GPa, a bending strength of 779 ± 47 MPa and a fracture toughness of 5.41 ± 0.29 MPa·m1/2 were obtained. The effects of three cutting parameters, namely cutting speed, feed rate and depth of cut on cutting tool performance were investigated, and the wear mechanisms of cutting tools were studied. The study published in [13] demonstrates the potential of cutting tools made of ZTA composites with in-situ formed SrAl12O19 as a solution for the woodworking industry, offering an alternative to conventional single carbide tools (WC+Co group). The cutting performance and failure mechanisms of ZTA-MgO (ZTA/MgO/MWCNT) ceramic cutting inserts reinforced with multilayer carbon nanotubes (MWCNTs) during continuous dry turning of hardened AISI 4340 steel (≈40 HRC) at high cutting speeds were studied in [14]. ZTA/MgO/ MWCNT tools showed improved performance compared to ZTA/MgO tools, especially in the cutting speed range of 200‑300 m/min. The increased microhardness, nanohardness and fracture toughness of ZTA/MgO/ MWCNT tools contributed to a significant improvement in cutting performance, especially at high cutting speeds, low feed rates and minimum depth of cut. In [15], a new self-lubricating ceramic cutting insert was developed by incorporating 10 wt. % molybdenum (Mo) into a ZTA composite by pressureless sintering. Temperatures encountered during high-speed turning of AISI 4340 steel resulted in the formation of thin lubricating tribofilms of Mo oxides (MoO2 and MoO3) in the contact zone. The self-lubricating properties of the developed insert successfully resisted abrasion and provided an 11 % increase in tool life over common cutting tools. Singh et al. [16] studied the machining of AISI 4340 steel using hot-pressed ZTA and ZTA-CuO inserts under optimized cutting conditions: cutting speed of 300 m/min, feed rate of 0.16 mm/rev and depth of cut of 0.5 mm. Due to the increased fracture toughness, the CuO-reinforced ZTA cutting insert achieved longer tool life (20 min) together with a 20 % reduction in wear on the back surface at the end of machining compared to the monolithic insert. During dry machining, the maximum temperature can exceed 1,000 °C [16]. Most high-speed steels and carbide cutting tools fail under these conditions due to excessive wear, resulting in poor tool life [16]. However, dry machining is a promising approach for economical, efficient and safe machining. Effective implementation of dry machining requires research and evaluation of the cutting process mechanism, cutting tool design and material, and equipment associated with the machining process [2, 15, 17, 18]. Innovations in self-lubricating cutting inserts have positioned dry machining as an attractive manufacturing technology with minimal environmental impact, resulting in a number of positive environmental consequences [15]. Ceramic tools made of ZTA ceramics have demonstrated exceptional high-temperature stability, fracture
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