JP2514088B2 - High hardness and high toughness sintered alloy - Google Patents

Description

TECHNICAL FIELD The present invention relates to a sintered alloy suitable as a material for a cutting tool or a material for an abrasion resistant tool, and more specifically, a heat-resistant alloy or a heat-resistant alloy.
The present invention relates to a sintered alloy suitable as a material for a cutting tool for cutting a difficult-to-cut material such as a Ti alloy.

(Prior art) A typical cemented alloy consisting of a hard phase containing WC as the main component and a binder phase containing Co as the main component is a cemented carbide alloy classified according to the JIS B4104 usage classification symbol. . These cemented carbides include WC-TiC-TaC- which is said to be a cemented carbide for steel cutting.
There are Co-based cemented carbides and WC-Co-based cemented carbides that are used for casting cutting or for dies and centers. Among these cemented carbides, the WC-TiC-TaC-Co cemented carbide has high hardness at high temperature due to the inclusion of TiC and TaC, and has excellent wear resistance, plastic deformation resistance and heat resistance at high temperatures. In contrast,
WC-Co based cemented carbide tends to have excellent strength and fracture toughness values.

An attempt has been made to develop an alloy that has both the advantages of this WC-TiC-TaC-Co cemented carbide and WC-Co cemented carbide.
Typical examples thereof are proposed in Japanese Patent Laid-Open Nos. 51-124607, 61-195951 and 61-207544.

(Problems to be Solved by the Invention) In JP-A-51-124607, Co4 to 13 vol%, one or more of titanium carbide, tantalum carbide, niobium carbide and vanadium carbide, 10 to 60 vol%, In a tungsten carbide-based cemented carbide having a composition of tungsten carbide and unavoidable impurities: the balance, tungsten carbide as a dispersed phase has an average particle size of 3 μm or less and a particle size of 5 μm.
The solid solution carbide, which is a dispersed phase, has an average particle size of 0.7 μm or less and a particle size of 1 μm.
Disclosed is a tough tungsten carbide based cemented carbide for a cutting tool, characterized by the fact that nothing exceeding m is present. Although the cemented carbide disclosed in this publication is an excellent alloy having both inherently contradictory properties of wear resistance, impact resistance and thermal shock resistance, it has a high strength, especially a fracture toughness. Due to the insufficient strength judged from the values, there is a problem that the cutting edge is likely to be cracked and chipped when it is used as a cutting tool for cutting a heat-resistant alloy which has a large deformation stress and is easily work hardened.

JP-A-61-195951 discloses that tungsten carbide is the main component, vanadium carbide or zirconium nitride is contained as a hard phase in an amount of 0.2 to 0.8 wt% and cobalt is used as a binder phase in an amount of 4 to 20%.
In cemented carbide consisting of wt%, the particle size of the carbon tungsten is at 0.6μm or less, high toughness cemented carbide, characterized in that and the Rockwell hardness H _R A91 or transverse rupture strength is 350 kgf / mm ² or more Alloys are disclosed. The cemented carbide disclosed in this publication is said to have high hardness and high toughness by having high transverse rupture strength, but the hardness at high temperature is low due to the fine grain size of tungsten carbide,
Moreover, since the fracture toughness value is also low, when used as a cutting tool for cutting steel or heat-resistant alloy, for example, there is a problem of short life due to lack of heat resistance and crack propagation resistance.

JP 61-207544 A discloses a hard phase containing WC as a main component.
93 to 97% by weight (however, one or two of TaC and NbC should be 0.1 to
Disclosed is a cemented carbide, characterized in that (5 wt% replaceable) is bonded in a binder phase consisting of Co and Ni in an amount of 3 to 7 wt% and the ratio Co / Ni of Co / Ni is set to 1/9 to 9/1. Has been done. Although the cemented carbide disclosed in this publication has improved toughness without lowering hardness, it has a cutting edge that is strong against mechanical and thermal repetitive stress when used as a cutting tool. However, since the fracture toughness value is almost the same as that of the conventional cemented carbide and the hardness at high temperature is low, there is a problem that it cannot be used as a cutting tool for cutting steel or heat-resistant alloy.

The present invention has solved the above problems, and specifically, has a high fracture toughness value and WC-TiC-TaC-Co cemented carbide which are one of the advantages of WC-Co cemented carbide. The purpose of the present invention is to provide a sintered alloy that has one of the advantages of alloys, that is, high hardness at high temperature, and that is suitable as a cutting tool for cutting difficult-to-cut materials such as heat-resistant alloys and Ti alloys. To do.

(Means for Solving Problems) When the present invention uses a cutting tool to cut a heat-resistant alloy such as Inconel that has a large deformation stress and is easily work-hardened, the cutting tool of the cutting tool is used during cutting. We have been considering to solve the problem that the temperature up to the cutting edge becomes considerably high, and therefore plastic deformation of the cutting edge and welding with the work material are more likely to occur than in the case of other work materials. Firstly, in order to enhance the plastic deformation resistance of a cutting tool, for example, in the case of cemented carbide, tungsten carbide is made into coarse grains, and carbides and carbonitrides of 4a, 5a, 6a group metals in the periodic table are used. And a so-called WC-TiC-TaC-Co cemented carbide containing at least one of these cubic compounds is preferable,
Further, in order to enhance the welding resistance to the work material, it is preferable to contain a cubic compound and reduce the amount of binder phase such as Co. Plastic deformation resistance and welding resistance to the work material It has been found that a high hardness at a high temperature is preferable as a standard for improving the property.

Secondly, as a result of observing the tool loss state when cutting difficult-to-cut materials such as heat-resistant alloys, it is found that the cracks generated at the boundary damage part of the tool gradually progress and lead to the loss. It is necessary to increase the fracture toughness value in order to prevent the progress, and in order to increase the fracture toughness value, for example, in the case of cemented carbide, it is preferable that the tungsten carbide has coarse grains. This finding was contrary to the first finding that it is preferable that the amount of the system compound is small and the amount of the binder phase is large.

Based on these first and second findings, by further optimizing the alloy structure and composition including the grain size of tungsten carbide, the amount of cubic compound and the amount of binder phase, high hardness and high hardness at high temperature were obtained. The present invention has led to the completion of the alloy of the present invention having a fracture toughness value.

That is, the high hardness and high toughness sintered alloy of the present invention comprises at least one hard phase in carbides, carbonitrides and mutual solid solutions of 4a, 5a and 6a metals of the periodic table, Co and Co. / Or a sintered alloy consisting of a binder phase containing Ni as a main component and unavoidable impurities, wherein the hard phase is a carbide, a carbonitride of a metal of group 4a, 5a, 6a of the periodic table or a mutual solid solution thereof. 3 to 10 VOl% of at least one cubic compound and 78 to 89 VOl% of tungsten carbide, and the binder phase is 8 to 12 VOl.
% Becomes, the upstanding orthorhombic compound is an average particle diameter of 0.5 to 1.0 [mu] m, carbon, tungsten is an average particle diameter of 1 to 25 m, the fracture toughness of said sintered alloy is 10.3MN · m ^-3/2 Above, and Miroku Vickers hardness at 1000 ℃ 420
The above is a feature.

The hard phase in the high hardness and high toughness sintered alloy of the present invention is specifically, for example, TiC, ZrC, HfC, VC, NbC, TaC, Cr.
₃ C ₂ , Mo ₂ C, WC, Ti (C, N), Zr (C, N), Hf (C, N), V (C,
N), Nb (C, N), Ta (C, N), (W, Ti) C, (W, Zr) C, (Ta,
Ti) C, (W, Ta, Ti) C, (W, Ta, Nb, Ti) C, (W, Ti) (C,
N), (W, Ta, Ti) (C, N), (W, Ta, Nb, Ti) (C, N) and the like. This hard phase is composed of WC and, for example, Ti
C, ZrC, HfC, VC, NbC, TaC, Ti (C, N), Ta (C, N), (W, Ti)
C, (W, Ta, Ti) C, (W, Ta, Nb, Ti) C, (W, Ta, Ti) (C, N)
And a cubic compound having a cubic crystal structure, such as tungsten carbide.
When the cubic compound is contained in an amount of up to 89 vol% and 3 to 10 vol% of the whole, it is preferable as a cutting tool material for difficult-to-cut materials such as heat resistant alloys. Further, the crystal grain size of the tungsten carbide constituting this hard phase has an average grain size of 1-2.
It is preferable that the fine tungsten carbide having a particle size of 0.5 μm or less is 2% or less of the entire tungsten carbide and the coarse tungsten carbide having a particle size of 3.5 μm or more is not present, and that the crystal of the cubic compound is 5 μm. The average particle size is 0.
It is also preferable to use uniform particles having a particle size of 5 to 1.0 μm and a particle size of more than 1.5 μm and no cubic compound.

The binder phase in the high-hardness and high-toughness sintered alloy of the present invention specifically includes, for example, Co, Ni, Co-Ni alloys or 4a, 5a, 6a group metals or Fe constituting the hard phase in these alloys and trace amounts of Fe. The total amount of this binder phase is 8-12 vo
It is preferable that the content is 1%.

To produce the high strength and high toughness sintered alloy of the present invention,
Although it is possible to perform the manufacturing process from the blending of the starting materials to the sintering in a conventional manner, especially in the composition components of the starting materials, the particle size and particle size distribution of the starting materials, and the mixing and grinding process of the starting materials. Strict control is important together with adjustment of particle size. For example, after sintering, a predetermined amount of powder for forming the cubic compound and a predetermined amount of powder for forming the binder phase are first mixed and pulverized to obtain an average particle size of the powder for forming the cubic compound. The diameter is 0.7-1.0 μm,
Next, add tungsten carbide powder that has an average particle size of approximately 2.5 μm and does not contain coarse particles of 3.5 μm or more, and secondarily mix and pulverize in a short time to suppress the crushing of tungsten carbide powder and uniformly mix it. The above method is preferable because the high hardness and high toughness sintered alloy of the present invention can be easily obtained. Of course, in order to produce a high hardness and high toughness sintered alloy of the present invention, as in the conventional cemented carbide or cermet, the carbon content, the nitrogen content and the unavoidable impurities such as oxygen content, CaO content and CaS content. And control
It is also necessary to strictly control the porosity of the obtained sintered alloy.

(Operation) In the high hardness and high toughness sintered alloy of the present invention, the hard phase mainly acts to increase the hardness of the sintered alloy at 1000 ° C.,
Although the binder phase mainly acts to increase the fracture toughness value, the control of factors such as the compositional components of the sintered alloy, the grain size of the hard phase, the amount of the hard phase, and the amount of the binder phase is essentially a conflict. It is possible to simultaneously increase the hardness at 1000 ° C. and the fracture toughness value, which are the alloy properties of the alloy.

(Example) Example 1 Uniform WC powder (a-WC) having a particle size of 2.5 to 3 m, particle size 1
The respective samples shown in Table 1 were compounded using TiC powder, TaC powder of less than μm and Co powder of about 1 μm. Of these compounded powders, TiC, TaC and Co powders were put into a stainless steel container together with φ6mm cemented carbide balls and acetone, and after 48 hours of primary mixing and grinding, WC powder was added and further Secondary mixing and pulverization for 15 hours was performed to obtain a mixed powder. After drying this mixed powder, paraffin was added and the mixture was pressed at a pressure of 1 ton / cm ² using a mold to obtain a molded body. The paraffin in the molded body was heated and volatilized, and then sintered under the conditions of a vacuum of 10 ^-2 torr and a temperature of 1420 ° C. and a holding time of 1 hour to obtain products 1, 2 and 3 of the present invention.

As a comparison, WC powder (b-WC) with an average particle size of 1 μm, WC powder (c-WC) with an average particle size of 2.8 μm, and an average particle size of 3.5 μm
Each sample shown in Table 1 was compounded using the WC powder (d-WC) and the above-mentioned powders of TiC, TaC, and Co. These compounded powders were put into a stainless steel container together with a cemented carbide ball having a diameter of 6 mm and acetone, and mixed and pulverized for 63 hours to obtain a mixed powder. This mixed powder was molded and sintered in the same manner as the above-described product of the present invention to obtain comparative products 1 to 6.

Each of the inventive products 1, 2, 3 and the comparative products 1, 2, 3, 4, 5, 6 thus obtained was observed with a metallurgical microscope for the grain size of the hard phase, and the hardness at room temperature was 1000 ° C. The fracture toughness values were obtained by the method of indentation of the hardness and Vickers hardness, and the respective results are shown in Table 2.

Example 2 Using the products 1 to 3 of the present invention and the comparative products 1 to 6 obtained in Example 1, a cutting test was conducted under the following cutting conditions (A) to (I), and the results are shown in Table 3. Indicated.

(A) Cutting Conditions Workpiece Inconel 718 (H _R C 41.8) chip shape CNMG one hundred and twenty thousand four hundred and eight cutting speed 30 m / min Depth of cut 1.5mm Feed 0.3 mm / rev Cutting oil used, the evaluation average flank wear V _B = 0.4 mm cutting time to reach (B) cutting conditions workpiece Inconel 718 (H _R C 41.8) chip shape CNMG one hundred twenty thousand four hundred and eight cutting speed 40 m / min Depth of cut 1.5mm feed 0.3 mm / rev cutting oil used, evaluate the average flank wear V cutting time to reach the _B = 0.4 mm (C) cutting condition (intermittent cutting) workpiece Inconel 718 (H _R C 41.8) 4 this slot input chip shape CNMG one hundred twenty thousand four hundred and eight cutting speed 20 m / min Depth of cut 1.0mm feed 0.1mm / rev cutting oil used, evaluate chipping or number of impacts until defect occurs (D) cutting conditions workpiece Naimonikku 80A (H _R C 37.9) chip shape CNMG 120 408 cutting speed 30 m / min Depth of cut 1.5mm feed 0.3 mm / rev Evaluation Cutting until reaching average flank wear amount V _B = 0.3 mm Time (E) Cutting Conditions Workpiece Naimonikku 80A (H _R C 37.9) to reach the chip shape CNMG one hundred twenty thousand four hundred and eight cutting speed 40 m / min Depth of cut 1.5mm Feed 0.3 mm / rev rate Average flank wear V _B = 0.3 mm cutting time (F) cutting conditions (intermittent cutting) workpiece Naimonikku 80 (H _R C 37.9) 4 this slot input chip shape CNMG one hundred and twenty thousand four hundred and eight cutting speed 20 m / min Depth of cut 1.0mm feed 0.1 mm / rev cutting oil used, evaluate chipping Or the number of impacts before chipping (G) Cutting conditions Work material Ti-6Al-4V alloy Chip shape CNMG 120408 Cutting speed 40m / min Depth of cut 1.5mm Feed 0.3mm / rev Cutting oil used, evaluation Average flank wear Cutting time until reaching V _B = 0.4mm (H) Cutting conditions Work material Ti-6Al-4V alloy Chip shape CNMG 120408 Cutting speed 60m / min Depth of cut 1.5mm Feed 0.3mm / rev Using cutting oil, evaluation average clearance surface wear amount V _B = cutting time to reach 0.4 mm (I) off Conditions number of impacts until (interrupted cut) Work material Ti-6Al-4V alloy four slots incoming chip shape CNMG one hundred twenty thousand four hundred and eight cutting speed 30 m / min Depth of cut 1.0mm Feed 0.1 mm / rev Cutting oil used, the evaluation chipping or defect occurs (Effect of the invention) As a result of the above, the high hardness and high toughness sintered alloy of the present invention is
Both the hardness and the fracture toughness value at 1000 ° C, which were considered to be antinomy characteristics in the conventional sintered alloy, are excellent in balance, and as a result, Inconel, Nimonic When used as a cutting tool material for cutting a heat-resistant alloy or a Ti alloy, it exerts an effect of excellent wear resistance and impact resistance in a well-balanced manner.

Claims (1)

(57) [Claims] 1. A hard phase of at least one of carbides, carbonitrides, and mutual solid solutions of metals of groups 4a, 5a, and 6a of the periodic table, and a binder phase containing Co and / or Ni as a main component. And a unavoidable impurity in the sintered alloy, wherein the hard phase is at least one cubic compound of carbides, carbonitrides of group 4a, 5a, and 6a metals of the periodic table and their mutual solid solutions. Ten
vol% and 78 to 89 vol% tungsten carbide, the binder phase is 8 to 12 vol%, and the cubic compound has an average particle size.
0.5 to 1.0 μm, and the tungsten carbide has an average particle size of 1
~ 2.5μm, the fracture toughness value of the sintered alloy is 10.3MN ・
A high hardness and high toughness sintered alloy, characterized in that it has m ^−3/2 or more and a ^Mylo Vickers hardness at 1000 ° C. of 420 or more.