ІНСТРУМЕНТАЛЬНИЙ МАТЕРІАЛ З КУБІЧНОГО BN ДЛЯ ОБРОБКИ ВОЛЬФРАМО-КОБАЛЬТОВИХ ТВЕРДИХ СПЛАВІВ

• Date: 2023
• Main Authors: Петруша, Ігор, Мельнійчук, Юрій, Осіпов, Олександр, Мощіль , Віктор, Стратійчук, Денис, Смірнова, Тамара, Білявина, Надія, Ткач, Василь, Кузьменко, Євген, Садова, Юлія
• Format: Article
• Language: Ukrainian
• Published: Институт сверхтвердых материалов им. В. Н. Бакуля Национальной академии наук Украины 2023
• Subjects: графітоподібний гексагональний нітрид бору; високі тиски; пряме конверсійне спікання; кубічний BN; інструментальний матеріал; точіння цементованого твердого сплаву ВК 15.
• Online Access: http://altis-ism.org.ua/index.php/ALTIS/article/view/282
• Journal Title: Tooling materials science

The process of direct conversion sintering (DCS) of graphite-like hexagonal boron nitride (hBN), in which at sufficiently high parameters of thermobaric exposure, the formation of a single-phase polycrystalline structure exclusively on the basis of cubic BN is possible, was used to obtain a substantially pure (translucent) high-hard material for instrumental use (PcBN). To achieve the necessary p,T-conditions for complete hBN®cBN conversion, a toroidal high-pressure device (АВТТ-30) was applied. Translucent PcBN samples with a diameter of up to 12.2 and a thickness of 4.5 mm were obtained at a pressure of р=8–9 GPa and a temperature of T >2250 °C with a process duration of 40 s. X-ray studies showed the presence of a strong axial texture [111] in the material, such that its axis is normal to the end surface of the sample. The highest reticular density of the (111) planes of cBN crystallites and their substructural features determine the extremely high hardness of this surface. So, when testing using the Vickers pyramid, HV = 80.9 GPa (load F=49 N). The thermal conductivity of the obtained PcBN at 300 K was l @ 195,4 ± 2,3 W/(m×K). The wear resistance test of the materials in the cutting tool was performed in extreme conditions of mechanical processing – turning of parts made from cemented carbide (WC-Co, VK 15 grade). In comparison with the cutting ceramics of the BH group based on cBN (~ 97 vol. %), the wear resistance of a PcBN cutter is 1.5–1.9 times higher, depending on the processing conditions. In addition, it is possible to increase the turning speed by approximately 2 times. It is expected that the obtained PsBN can be effective in milling titanium alloys, Co-Cr alloys and nickel-based heat-resistant alloys.