JPS63505B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] This invention has high hardness and high strength, and when used as a cutting tool, has excellent wear resistance and plastic deformation resistance, and is suitable for high-speed cutting that requires these properties. The present invention relates to a method for producing a coated ultra-hard sintered alloy that exhibits excellent cutting performance. [Conventional technology and its problems] In recent years, high-speed cutting has been considered in the cutting field to improve processing efficiency, but increasing the cutting speed increases the temperature of the cutting tool's cutting edge and causes the cutting edge to wear out. Rather, in many cases, the cutting tool reaches the end of its life or cannot be used due to plastic deformation due to high temperatures. For example, WC-based cemented carbide and TiC-based cermet, which are currently in practical use as cutting tools, each have a content of 4 to 20% by weight of Co and Ni, which are bonding metals.
(Japanese Industrial Standards), so the cutting edge temperature is 1000℃.
If the cutting speed exceeds 200 m/min, the cutting edge will suddenly soften, so it cannot currently be used for cutting at cutting speeds exceeding 200 m/min. On the other hand, for the purpose of improving the wear resistance of the above-mentioned WC-based cemented carbide, the surface of the WC-based cemented carbide is coated with elements from the periodic table.
Group 4a carbides, nitrides, carbonitrides, carbonates,
Coated cemented carbide for cutting with a surface coating layer consisting of one or more layers of oxynitrides, carbonate nitrides, and oxides and oxynitrides of Al has been put into practical use and has become the mainstream for throw-away chips. However, even with this coated cemented carbide, the base is
Since it is a WC-based cemented carbide containing 5 to 10% by weight of Co, there was a problem in that the cutting edge softened when the cutting speed exceeded 250 m/min. Therefore, for cutting at cutting speeds exceeding 250 m/min, Al ₂ O ₃ -based ceramics were considered, but
Due to the low strength of Al ₂ O _tri- based ceramics, which has a transverse rupture strength of 50 to 80 Kg/mm ² , its use has been limited to a portion of casting cutting. Therefore, attempts have been made to reduce the amount of Co in WC-based cemented carbide to improve the hardness of the alloy, which in turn improves its wear resistance during cutting, as well as its plastic deformation resistance. In both attempts, when the amount of Co in the WC-based cemented carbide is reduced,
Although the hardness and plastic deformation resistance of the alloy were improved, the transverse rupture strength was significantly reduced, resulting in an alloy with a strength equivalent to that of the above-mentioned ceramics, making it impossible to put it to practical use. [Object of the Invention] Therefore, the object of the present invention is to provide a material that has higher strength than the above-mentioned ceramics, has strength comparable to general WC-based cemented carbide, and has higher hardness and plastic deformation resistance. The object of the present invention is to produce a material that can also be used as a cutting tool for high-speed cutting in excess of /min. [Prior Art and Knowledge] The present inventors previously discovered a composite metal carbonitride solid solution powder having a composition formula: (M, W) (C, N) (where M = Ti, Zr, and Hf). (one type or two or more types): 20 to 90% by weight, tungsten carbide (hereinafter referred to as WC) powder: 10 to 80% by weight, Co powder: 0.5 to 3% by weight. By sintering it in a nitrogen atmosphere, it has fewer small pores and has a hardness of Rockwell A hardness (hereinafter referred to as HRA).
We have discovered that it is possible to obtain a superhard sintered alloy with high hardness and strength, with a transverse rupture strength of 92.5 or higher and a transverse rupture strength of 150Kg/ ^mm2 or higher. Using such an alloy as a substrate, carbides, nitrides, carbonitrides, carbonates, oxynitrides, and carbonitrides of group 4a of the periodic table of elements are formed on the surface of the alloy.
and one of Al oxides and oxynitrides
Forming a surface coating layer or a surface coating layer consisting of two or more layers improves the plastic deformation resistance of the entire coated ultra-hard sintered alloy, and also prevents peeling of the surface coating layer due to plastic deformation of the base, making it difficult to use conventional WC. Compared to coated WC-based cemented carbide, in which the surface of the base cemented carbide is coated with the above-mentioned hard material, the wear resistance improvement rate due to the surface coating layer is extremely high, and as a result, the cutting speed exceeds 250 m/min. It was discovered that it exhibits excellent cutting performance even when used as a cutting tool at high speeds. [Matters Essential to the Structure of the Invention] The present invention is a method for producing a coated ultra-hard sintered alloy for cutting tools based on the above-mentioned knowledge. C, N)
Composite metal carbonitride solid solution powder having (however,
M: one or more of Ti, Zr, and Hf), tungsten carbide powder, and Co powder are prepared, and these raw material powders are mixed in weight% as follows: Composite metal carbonitride solid solution powder: 20 to 90 %, tungsten carbide powder: 10~80%, Co powder: 0.5~3%, mixed under normal conditions, formed into a green compact, sintered in a nitrogen atmosphere, and then An ultra-hard sintered alloy base for a cutting tool having hardness and high strength is manufactured, and then at least the cutting surface of the ultra-hard sintered alloy base is coated with carbides, nitrides, etc. of group 4a of the periodic table of elements,
It is characterized by forming a surface coating layer consisting of one or more layers of carbonitrides, carbonates, oxynitrides, carbonate nitrides, and oxides and oxynitrides of Al. [Constituent elements of the invention] The configuration of the present invention will be explained in detail below. () Regarding manufacture of the substrate (i) Particle size of raw powder In order to improve the transverse rupture strength of the alloy obtained for both the composite metal carbonitride solid solution powder and the WC powder, it is desirable that the powder particle size be fine. For example, the average particle size of the composite metal carbonitride solid solution powder is preferably within the range of 0.5 to 5.0 μm, and the average particle size of the WC powder is preferably within the range of 0.5 to 5.0 μm. It is desirable that the Co powder has an average particle size within the range of 0.5 to 3.0 μm. (ii) Mixture composition (a) (M, W) (C, N) This component is the first hard dispersed phase forming component of the alloy produced by this invention, and the composition changes when nitrided. death,
Improves the sinterability of the alloy, makes it a dense sintered body, and improves the transverse rupture strength of the alloy. In addition, since the solid solution contains one or more of Ti, Zr and Hf as essential metal components, it itself has a high hardness and thus has the effect of improving the hardness of the alloy. If the content is less than 20% by weight, the desired effect described above cannot be obtained, while if it exceeds 90% by weight, the transverse rupture strength of the alloy will decrease. %. (b) WC WC is the second hard dispersed phase-forming component of the alloy obtained by this invention, and the above (M, W) (C, N) inhibits the formation of skeletons and inhibits the hard phase-forming component. It has the effect of improving dispersion and improving the transverse rupture strength of the alloy, but if the combined amount is less than 10% by weight, the desired effect described above cannot be obtained;
If the content exceeds 10 to 80, the wear resistance during cutting will decrease.
It was determined as weight%. (c) Co Co is the conventional WC in this invention.
The above (M, W), which is the main component of the alloy, plays a catalytic role rather than a binding metal role like Co in the base cemented carbide.
It has the effect of making it easier to change the solid solution composition due to nitridation of (C, N), significantly improving the sinterability of the alloy, and greatly improving the resistance of the alloy. It is effective with a smaller amount of Co than that contained in Co. If the content is less than 0.5% by weight, the above effects will not be sufficient, while if it exceeds 3% by weight, the hardness will decrease and the wear resistance during cutting will also decrease, making it different from conventional WC-based cemented carbides. Since there is no difference in wear resistance, the content can be reduced.
The content was determined to be 0.5 to 3% by weight. In this invention, in addition to the above three components,
Up to 2% by weight of TaC, NbC, VC, Cr ₃ C _2, etc., which are added to WC-based cemented carbide as a WC grain growth inhibitor, may be added. (iii) Mixing Mixing is carried out under normal conditions, e.g. in a ball mill.
This is done by wet grinding (eg in alcohol) mixing for 72 hours. (iv) Molding After drying the powder mixture, it is press-molded at a pressure of 10 to 30 kg/mm ² to form a green compact. (v) Sintering Sintering needs to be carried out in a nitrogen atmosphere in order to nitride the composite metal carbonitride solid solution, change its composition, and improve the sinterability of the alloy. The nitrogen pressure is preferably 0.01 atm or higher. This is because the nitridation of the composite metal carbonitride solid solution does not proceed sufficiently if the pressure is less than 0.01 atmosphere. The sintering temperature is preferably 1400 to 1800°C. If the temperature is lower than 1400℃, many large cavities will remain in the sintered compact and the transverse rupture strength of the alloy will decrease.On the other hand, if the temperature exceeds 1800℃, the ( This is because M, W) (C, N) and WC cause grain growth, resulting in a decrease in transverse rupture strength. () Regarding the formation of the surface coating layer (i) Layer structure The surface coating layer consists of carbides, nitrides, carbonitrides, carbonates, oxynitrides, and carbonitrides of group 4a of the periodic table of elements, and oxides of Al. and one or more layers of oxynitride. Group 4a of the periodic table of elements is Ti, Zr and Hf
It is a group consisting of. Therefore, carbides, nitrides, carbonitrides of group 4a of the periodic table of elements,
One or more layers of carbonates, oxynitrides, carbonate nitrides, and oxides and oxynitrides of Al are Ti carbides, nitrides,
Carbonitrides, carbonates, oxynitrides and carbonitrides, Zr carbides, nitrides, carbonitrides, carbonates, oxynitrides and carbonitrides, Hf carbides, nitrides, carbonitrides, carbonates , oxynitrides, carbonate nitrides, and oxides and oxynitrides of Al, or one or more of the above-mentioned layers are sequentially stacked thereon. (ii) Average layer thickness The average layer thickness of the entire surface coating layer consisting of one or more layers is preferably 0.5 to 20 μm. This is because if the average layer thickness is less than 0.5 μm, the desired wear resistance cannot be ensured, whereas if the average layer thickness exceeds 20 μm, the toughness of the coated ultra-hard sintered alloy will significantly deteriorate. (iii) Layer formation method Formed by ordinary chemical vapor deposition or physical vapor deposition. [Example] Next, the configuration and effects of the present invention will be explained in detail using Examples and Comparative Examples. Examples and Comparative Examples Each raw material powder was blended into the composition shown in Table 1, wet-pulverized and mixed in a ball mill for 72 hours, dried, and then press-molded at a pressure of 15 kg/mm ² .

【table】

[Table] Comparative ultra-hard sintered alloy substrates 1 to 1 to 22 of the ultra-hard sintered alloy substrates of the present invention were obtained by forming a green compact and then sintering this green compact under the sintering conditions shown in Table 1. -6 were produced. The HRA and transverse rupture strength of the substrate are also shown in Table 1. In addition, comparative ultra-hard sintered alloy substrate 1
Comparative ultra-hard sintered alloy substrates 5 to 5 have compounding compositions that are outside the compounding composition range of this invention (the compounding ratios of components that are out of the compounding composition range of this invention are marked with *). Further, this invention differs from the present invention in that it is sintered in a vacuum rather than in a nitrogen atmosphere (indicated by *). Furthermore, the comparative ultra-hard sintered alloy substrate 6 differs from the present invention only in that it is sintered in a vacuum instead of in a nitrogen atmosphere (indicated by *). Next, cutting chips in the shape of CIS/SNP432 were manufactured from these substrates. The entire surface of these chips is coated with TiN using the usual chemical vapor deposition method (when coating TiC in a heat-resistant alloy reaction vessel, react by flowing TiCl ₄ , CH ₄ , and H ₂ gases at 1000°C) to coat TiN. TiCl ₄ , N ₂ , H ₂
When reacting gases at 1000°C to coat Ti carbonate, react with TiCl ₄ , CO ₂ , H ₂ gas at 1000°C, and when covering Al ₂ O ₃ use AlCl ₃ , CO ₂ ,
React _H2 gas at 950℃. Further, when coating a composite compound, a coating layer is formed by appropriately mixing various gases and reacting them. ), a surface coating consisting of 1 to 3 layers with the layer structure shown in Table 2 (the formulas representing the compounds constituting the layers are written stoichiometrically) and the average layer thickness of each layer. Inventive coated ultra-hard sintered alloy chips 1-29 and comparative coated ultra-hard sintered alloy chips 1-6 were prepared by forming layers. Next, these cutting chips were tested for high-speed continuous cutting of steel under the following conditions: Work material: SNCM8 (Brinell hardness: 240) round bar cutting conditions: Cutting speed: 300 m/min Feed: 0.3 mm/rotational depth of cut: 1mm Cutting time: 10 minutes and high-speed interrupted cutting test of cast iron under the following conditions Work material: FC25 (Brinell hardness: 140) grooved round bar Cutting conditions Cutting speed: 270m/min Feed: 0.3mm/ Rotary depth of cut: 2 mm Cutting time: 10 minutes. In the high-speed continuous cutting test on steel, the wear width of the cutting edge and the wear depth on the rake face were measured, and in the high-speed intermittent cutting test on cast iron, the flank wear width and crater wear were measured. The depth was measured and the results are shown in Table 2. For the purpose of comparison, comparative ultra-hard sintered alloy chips 1 to 5 were prepared from the ultra-hard sintered alloy substrates 4, 5, 6, 8, and 9 of the present invention without a surface coating layer.
WC-based cemented carbide chip equivalent to P10 (conventional alloy chip 1; composition is 73% WC - 15% TiC - 5% TaC - 7
%Co), WC-based cemented carbide chip equivalent to KO5

【table】

【table】

〔Effect of the invention〕

As described above, the coated super hard sintered alloy of the present invention is
The base material has high hardness and strength, and has excellent plastic deformation resistance, so by depositing a hard coating layer on the surface of this base material, when used as a cutting tool, it is practically impossible to use with conventional alloys or conventional coated alloys. This enabled high-speed cutting of over 250 m/min, which was previously impossible.

Claims (1)

[Claims] 1. As raw material powder, composition formula: (M, W) (C,
A composite metal carbonitride solid solution powder having N) (M: one or more of Ti, Zr, and Hf), tungsten carbide powder, and Co powder are prepared, and these raw material powders are %, composite metal carbonitride solid solution powder: 20-90%, tungsten carbide powder: 10-80%, Co powder: 0.5-3%, mixed under normal conditions, and made into a green compact. and then sintered in a nitrogen atmosphere to produce an ultra-hard sintered alloy base for a cutting tool having high hardness and high strength, and then, on at least the cutting surface of the ultra-hard sintered alloy base, carbides and nitrides of group 4a of the periodic table of elements;
A coating for a cutting tool characterized by forming a surface coating layer consisting of one or more layers of carbonitride, carbonate, oxynitride, carbonitride, and oxide and oxynitride of Al. A method for producing ultra-hard sintered alloys.