JPS6131072B2 - - Google Patents

Description

[Detailed description of the invention]

This invention has high hardness, wear resistance, toughness,
High-hardness steel and Ni
The present invention relates to ultra-high pressure sintered tool materials suitable for use as cutting tools, bearings, wire drawing dies, etc., such as base or Co-base superalloys. Conventionally, tungsten carbide-based cemented carbide, which has excellent toughness, has generally been widely used for the above-mentioned applications, but in recent years, as usage conditions have become more severe, better tool materials have been sought. development is strongly desired. Recently, in response to such demands, cubic boron nitride sintered materials and sintered materials containing small amounts of Al and iron group metals have been proposed and commercially available. Although it has excellent wear resistance, it lacks toughness, and the latter sintered material deteriorates in wear resistance especially when used under conditions that involve high heat generation. Currently, none of these materials have satisfactory properties. From the above-mentioned viewpoints, the present inventors have developed a method to replace cubic boron nitride in order to obtain a sintered tool material that has excellent toughness, high-temperature oxidation resistance (heat resistance), and wear resistance. As a result of research focusing on cubic boron carbonitride (hereinafter referred to as cubic BNC), which has high hardness and high toughness, it was found that cubic BNC powder contains carbides, nitrides, and boron of group 4a metals of the periodic table. oxides, carbides and nitrides of Group 5a metals, carbides of Group 6a metals, and these two
solid solutions of more than one species, and one or more of the group consisting of aluminum oxide, aluminum nitride, silicon carbide, silicon nitride, boron carbide, and yttrium oxide (hereinafter collectively referred to as compounds) They found that if the blended powders were homogeneously mixed and sintered under ultra-high pressure, a sintered tool material with good toughness, heat resistance, and wear resistance could be obtained. Therefore, this invention was made based on the above knowledge, and has a composition consisting of: cubic BNC: 10 to 90%, compound: 10 to 90%, and unavoidable impurities: 5% or less, in terms of volume %. It is an ultra-high pressure sintered tool material with excellent toughness, heat resistance, and wear resistance. Next, the reason why the composition range of the ultra-high pressure sintered tool material of the present invention is limited as described above will be explained. (a) Cubic BNC Cubic BNC is produced by mixing BNC powder with a hexagonal or amorphous crystal structure, that is, BxNyCz powder, in a small amount with iron group metal powder and sealing it in a metal container for sintering. It is synthesized by converting it into a cubic crystal structure by holding it for a predetermined period of time at a temperature of 1200°C or higher and a pressure of 40Kb or higher, preferably at a temperature of 1500°C or higher and a pressure of 70Kb or higher using a known ultra-high pressure and high temperature generator. The resulting cubic crystal structure BxNyCz has x=y, and z is usually in the range of 0.1<z<5.0. Therefore, in the following description, BNCz
Using a simple expression, x=y=1. Cubic BNC has extremely high hardness, chemical stability, and excellent toughness, but if its content is less than 10% by volume, it will not have the desired wear resistance. On the other hand, if the content exceeds 90% by volume, the content of the compound will be relatively too small and the toughness and heat resistance will decrease. It was set at 90% capacity. (b) Compounds All of these compounds have high melting points and high hardness, as well as excellent oxidation resistance at high temperatures.Furthermore, they promote grain boundary diffusion during sintering to form strong interparticle bonds. Since it has excellent sinterability, it forms a dense structure and has the effect of improving toughness, but if its content is less than 10% by volume, the desired effect cannot be obtained; If the content exceeds 10 to 90% by volume, the content of cubic BNC will be relatively too small and it will be impossible to secure the desired wear resistance.
It was determined that (c) Unavoidable impurities Unavoidable impurities consist of small amounts of iron group metals that are mixed during cubic BNC synthesis, iron group metals and tungsten carbide that are mixed in from mixing containers when mixing raw material powder during material production. However, since it does not have any adverse effect on the material properties even if it is contained up to 5% by volume, the upper limit was set at 5% by volume. Furthermore, the tool material of the present invention is obtained by blending the cubic BNC powder synthesized as described above and a compound powder in a predetermined ratio, mixing for a long time to make a homogeneous mixed powder, and then adding the mixed powder to a metal. It is then placed in an ultra-high pressure and high temperature generator such as that described in Japanese Patent Publication No. 38-14, and the pressure and temperature are increased to a pressure of 40 Kb or more.
It is manufactured by maintaining the pressure and temperature at a temperature of 1200°C or more for about 5 minutes or more, and then releasing the pressure after cooling. Next, the ultra-high pressure sintered tool material of the present invention will be explained with reference to Examples. First, various amorphous BNC powders and Ni-Al alloy powders were mixed in a volume ratio of 90:10, mixed under normal conditions, and then sealed in a Ta container. Pressure: 70~ with high pressure and high temperature generator
80Kb, temperature: 1500-1700℃, holding time: 20 minutes, after cooling, pressure is released and taken out, followed by pickling, and separation treatment using a separation method that utilizes the difference in specific gravity. Various cubic BNCz (Z: 012, 0.8,
0.95, and 4.5) powder was produced. Next, in addition to these various BNCz powders with an average particle size of 3 μm, we prepared separately prepared BNCz powders of 0.2 to 3 μm.
Various compound powders having an average particle size within the range of After blending and wet mixing in a ball mill for 48 hours and drying, this mixed powder is made of stainless steel with an outer diameter of 12 mmφ.

【table】

[Table] Packed in a container and heated using a known ultra-high pressure and high temperature generator.
Predetermined maximum heating temperature within the range of 1400-1600℃, 30
By sintering at a predetermined maximum applied pressure within the range of ~60 Kb and a holding time of 10 minutes, cooling, and releasing the pressure, a composition that is substantially the same as the blended composition (but in both cases Invention ultra-high pressure sintered tool materials 1-27, comparative ultra-high pressure sintered tool materials 1-2, containing tungsten carbide and iron group metals mixed in from a ball mill etc. during mixing in a range of 4% or less as inevitable impurities) , and conventional ultra-high pressure sintered tool materials, respectively. In addition, comparative ultra-high pressure sintered tool materials 1 and 2 all have compositions in which any of the constituent components (those marked with * in Table 1) are outside the scope of the present invention. be. Next, for the various ultra-high pressure sintered tool materials obtained as a result, the Vickers hardness was measured for the purpose of evaluating wear resistance, and the fracture toughness value was measured for the purpose of evaluating toughness. A cutting edge is cut out using a cutting method, and this cutting edge is brazed to a WC (tungsten carbide)-based cemented carbide chip using silver solder to make a cutting tool. Work material: Hardness H _R C62. Bearing steel (JIS/
SUJ2), Cutting speed: 150m/min, Feed: 0.2mm/rev, Depth of cut: 0.5mm, Turning test on high hardness steel, Work material: Rene 41 Cutting speed: 80m/min, Feed: 0.2 Continuous cutting tests were conducted on Ni-based superalloy under the following conditions: mm/rev., depth of cut: 1 mm, and in each test, the cutting time until the flank wear width of the cutting edge reached 0.2 mm was measured. The measurement results are shown in Table 1. From the results shown in Table 1, the ultra-high pressure sintered tool materials 1 to 27 of the present invention all have excellent wear resistance and toughness, and fully demonstrate excellent performance in cutting tests. Although conventional ultra-high pressure sintered tool materials exhibit excellent wear resistance, they have poor toughness, so it is clear that they do not exhibit sufficiently satisfactory performance in cutting tests. Furthermore, as seen in Comparative Ultra-High Pressure Sintered Materials 1 and 2, if the content of any of the constituent components falls outside the scope of the present invention, at least one of the above properties may be lost. It is clear that the characteristics will be inferior. As mentioned above, the ultra-high pressure sintered tool material of this invention has excellent toughness, heat resistance, and wear resistance, so it can be used in high-hardness steel, Ni-based or Co-based superstructures that require these properties. It exhibits excellent properties when used as an alloy cutting tool, as well as in bearings, wire drawing dies, etc.

Claims (1)

[Claims] 1. Cubic boron carbonitride: 10 to 90%, carbides, nitrides, borides, and oxides of metals from group 4a of the periodic table, carbides, nitrides, and nitrides of metals from group 5a of the periodic table. Group 6a metal carbides, solid solutions of two or more of these, and one or more of the group consisting of aluminum oxide, aluminum nitride, silicon carbide, silicon nitride, boron carbide, and yttrium oxide: An ultra-high pressure sintered tool material having a composition (volume %) consisting of: 5 to 60%, inevitable impurities: 5% or less, and having particularly excellent toughness.