Polycrystalline cubic boron nitride and production method therefor

[0070] [First Embodiment: Cubic Boron Nitride Polycrystal]

[0071] A cubic boron nitride polycrystal according to one embodiment of the present disclosure will be described.

[0072]

[0073] The cubic boron nitride polycrystal of the present disclosure is a cubic boron nitride polycrystal containing more than 98.5% by volume of cubic boron nitride, wherein the dislocation density of the cubic boron nitride is greater than 8×10 15 / m 2 The cubic boron nitride polycrystal contains a plurality of crystal grains, and the median diameter d50 of the circle-equivalent diameters of the plurality of crystal grains is not less than 0.1 μm and not more than 0.5 μm.

[0074] The cubic boron nitride polycrystal of the present disclosure is a sintered body, but usually the sintered body is mostly intended to contain a binder, so the term "polycrystal" is used in the present disclosure.

[0075] When the cubic boron nitride polycrystal of the present disclosure is used as a tool, especi

[0168] [Second Embodiment: Manufacturing Method of Cubic Boron Nitride Polycrystal]

[0169] use Figure 1 to Figure 5 A method for producing the cubic boron nitride polycrystal of the present disclosure will be described. figure 1 is the pressure-temperature phase diagram of boron nitride. Figure 2 ~ Figure 4 It is a figure for demonstrating the manufacturing method of the cubic boron nitride polycrystal of this disclosure. Figure 5 It is a figure for demonstrating the conventional example of the manufacturing method of the cubic boron nitride polycrystal.

[0170] The method for producing a cubic boron nitride polycrystal of the present disclosure is the method for producing a cubic boron nitride polycrystal of the first embodiment. The manufacturing method of the cubic boron nitride polycrystal of the present disclosure includes: a first step of preparing hexagonal boron nitride powder (hereinafter, also referred to as "first step"); passing the hexagonal boron nitride po

[0259] In Example 1, the production conditions of the cubic boron nitride polycrystal, the composition (composition, median grain size, and dislocation density) of the obtained cubic boron nitride polycrystal, and the use of The relationship between tool life in the case of high-load machining of difficult-to-cut materials performed with cubic boron nitride polycrystalline tools was investigated.

[0260]

[0261] Cubic boron nitride polycrystals of Sample 1-1 to Sample 9 were prepared according to the following procedure.

[0262] (first process)

[0263] 6 g of hexagonal boron nitride powder (“Denka boron nitride” (trade name) manufactured by Denka Corporation, particle diameter: 5 μm) was prepared. The above-mentioned hexagonal boron nitride powder was filled into a capsule made of molybdenum, and set in an ultra-high pressure and high temperature generator.

[0264] (second process and third process)

[0265] [Sample 1-1, Sample 1-3, Sample 2-2, Sample 3-2, Sample 4 to S