JPS63109139A - Titanium carbide sintered alloy for cutting tool parts - Google Patents

Abstract

PURPOSE:To obtain the titled sintered alloy excellent in thermal shock resistance, wear resistance, etc., by specifying the proportion of a binding phase composed principally of Ni or Co to a hard phase with a specific grain size having a specific composition consisting of TiC, TiN, and carbides of group VIa metals. CONSTITUTION:The sintered alloy has a composition consisting of, by weight, 5-25% binding phase composed principally of Ni and/or Co and the balance hard phase containing 20-65% TiC, 18-40% TiN, and 15-40% of one or more kinds among the carbides of the metals of group VIa of the periodic table with inevitable impurities. Further, the above-mentioned hard phase is regulated so that average grain size is 1.0-2.0mum and the grains of <=0.5mum grain size comprise 1-10vol% of the total hard phase. On the other hand, the lattice constant of the above binding phase is regulated to 3.56-3.61Angstrom . Moreover, if necessary, the carbides or nitrides of the metals of group Va of the periodic table can be substituted for 5-31% of the above TiC in the above hard phase, or the carbides or nitrides of Zr of Hf can be substituted for 0.5-8% of the above TiC. In this way, the SiC sintered alloy for cutting tool parts excellent in thermal shock resistance, wear resistance, resistance to thermoplastic deformation, and breaking resistance at high temp. can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention aims to improve the ms impact resistance, which cannot be used in the range of applications ranging from conventional titanium carbide-based sintered alloys to tungsten carbide-based sintered alloys. The present invention relates to a titanium carbide-based sintered alloy for cutting tool parts that has excellent wear resistance, thermoplastic deformation resistance, and fracture resistance at high temperatures.

(Prior art) As for titanium carbide-based sintered alloys, carbide-based alloys represented by TiC-Mo2C-Ni-based sintered alloys were first developed, but compared to tungsten carbide-based sintered alloys, Because of its extremely poor thermoplastic deformation resistance and chipping resistance, it has been put to practical use in some cutting tool parts for high-speed finishing cutting.

By adding TiN or Ti(C,N) to this carbide alloy to suppress grain growth of the hard phase and refine it,
Titanium carbide-based sintered alloys containing nitrogen have achieved improvements in heat resistance, deformability, and fracture resistance.

Many nitrogen-containing titanium carbide sintered alloys have been proposed. In addition to JP-A No. 53-119205, which discloses TiN for mounting members, and JP-A No. 57-2860, which discloses it for wear-resistant J@, TiN or Ti(C,N) is generally used. The grain growth suppressing effect is used to make the hard phase finer and increase the strength.In particular, nitrogen-containing titanium carbide sintered bond and gold for cutting tool parts have an average grain size of 1 to 1. 2
#Lm starting material powder was mixed and ground, and due to the grain growth suppressing effect of TiN or Ti(C,N) added as a nitrogen source, the average particle size of the hard phase was 1 μm or less after sintering. It is something that exists.

In fact, among nitrogen-containing titanium carbide-based sintered alloys for cutting tool parts, the grain size of the hard phase of the sintered alloy is specified, but a representative example is JP-A-50-1025.
There is a publication No. 08.

(Problems to be Solved by the Invention) JP-A-50-102508 contains titanium nitride in an amount of 5 to 40% of the total amount of titanium carbide and titanium nitride,
The alloy contains at least one selected from the group consisting of W, Mo, Ta, and Nb in an amount of 15 to 40% as a carbide, is combined with 3 to 30% of iron group metal, and has no carbide or nitride crystals in the alloy. A sintered alloy is disclosed which is characterized in that the majority has a grain size of 14 m or less. The sintered alloy of JP-A-50-102508 has superior thermal shock resistance, abrasion resistance, and thermoplastic deformation resistance compared to titanium carbide-based sintered alloys that do not contain nitrogen. However, compared to tungsten carbide-based sintered alloys, so-called cemented carbides, which are the most common and widely used cutting tool parts, the alloy properties described above cannot be said to be sufficient, and they are susceptible to large thermal shocks, especially during severe interrupted cutting. Under such conditions, there is a problem that the life of the product is shortened due to defects caused by thermal cracking, making it impossible to put it into practical use.

The present invention improves the properties of titanium carbide-based sintered alloys for use in cutting tool parts, based on the conventional method of increasing the nitrogen content of the alloy and thereby refining the hard phase.
As a result, it was not possible to achieve the performance that cemented carbides deserve, but by increasing the nitrogen content, controlling the hard phase grain size to a relatively coarse grain size, and further strengthening the binder phase, , which solves the above-mentioned problems. Specifically, the hard phase containing 18 to 40% by weight of titanium nitride as a nitrogen source has an average particle size of 1.0 μm to 2.0 μm, and The hard phase with a grain size of .5#Lm or less accounts for 1-10% by volume of the total hard phase, significantly increasing thermal shock resistance, wear resistance, and thermoplastic deformation resistance, and covering the range of use of cemented carbide. The purpose of this invention is to provide a sintered alloy that can

(Means for Solving the Problem) The present inventors have discovered that in order to improve the thermal shock resistance and plastic deformation resistance of a nitrogen-containing titanium carbide-based sintered alloy, the grain size of the hard phase should be coarsened to some extent. Moreover, starting from the viewpoint that it is necessary to increase the mean free path of the bonded phase by increasing the amount of the bonded phase, we conducted an investigation and found that it was indeed possible to increase the mean free path of the bonded phase using the method described above. Although the thermal shock resistance is improved, the thermoplastic deformation resistance is decreased, resulting in the problem of causing defects due to thermoplastic deformation0.
Therefore, we divided the nitrogen-containing titanium carbide-based sintered alloy into both the hard phase and the binder phase and examined each.
) to (4) were obtained.

(1) #In order to improve thermal shock resistance, it is necessary to increase the amount of binder phase, and in order not to impair the thermoplastic deformability of the sintered alloy even if the amount of binder phase is increased, It is important to enhance the high temperature strength of the binder phase. for that,
The nitrogen content in the sintered alloy is 18% in terms of T i N.
In addition, the carbide of group 6a metal of the periodic table is contained in an amount of 15% or more, and the lattice constant of the bonded phase is 3.56 Å to 3.56 Å.
When exposed to 61 people, the binder phase of the titanium carbide-based sintered alloy has significantly superior high-temperature strength.

(2) By controlling the particle size of the starting raw material powder and controlling the manufacturing conditions from mixing and pulverization to sintering conditions, the average particle size of the hard phase of the sintered alloy can be adjusted to 1. oμm~2. Oμm and 0.
When the hard phase with a grain size of 5 μm or less accounts for 1 to 10% by volume of the total hard phase, the nitrogen-containing titanium carbide-based sintered alloy slows down the growth rate of thermal cracks and exhibits significantly excellent thermal shock resistance.

(3) Part of titanium carbide is 4a of the periodic table excluding Ti.
When nitrogen-containing titanium carbide-based sintered alloys are replaced with carbides or nitrides listed in the group metal notification, the thermoplastic deformation resistance is further improved.

(4) When part of the titanium carbide is replaced with a carbide or nitride of a group 5a metal in the periodic table, the thermal shock resistance of the nitrogen-containing titanium carbide sintered alloy is further improved.

The present invention has been completed based on the findings (1) to (4) above.

The titanium carbide-based sintered alloy for cutting tool parts of the present invention is made of NI
and/or a binder phase mainly composed of CO, 5 to 25% by weight, the remainder being 20 to 65% by weight of titanium carbide, and 18 to 18% of titanium nitride.
In a sintered alloy consisting of a hard phase containing 40% by weight and at least 115 to 40% by weight of carbides of group 6a metals of the periodic table and unavoidable impurities, the hard phase has an average grain size of 1.
．． 0 part m to 2.0 JLm, and the hard phase with a particle size of 0.5 gm or less accounts for 1 to 10% by volume of the total hard phase, and the bonded phase has a lattice constant of 3.56 Å to 3.5 gm. 61
It is characterized by being human.

The binder phase in the titanium carbide-based sintered alloy for cutting tool parts of the present invention is mainly composed of Ni and/or Co, and includes metals from groups 4a, 5a, and 6a of the periodic table forming the isthmus phase, and nitrogen. , at least one kind of carbon is dissolved in Ni and/or CO and plays a role of strengthening the binder phase, and in particular, in Ni and/or CO of group 6a metal of the periodic table. The amount of solid solution increases, and the thermoplastic deformation resistance is significantly improved.

In particular, when the lattice constant of the bonded phase is 3.56 Å to 3.61 as a guideline representing the total amount of the above-mentioned solute atoms dissolved in the bonded phase containing Ni and/or Co as the main component, It has excellent fracture resistance and thermoplastic deformation resistance. The lattice constant of this binder phase is particularly controlled by the amount of carbon in the alloy, and specifically by the total carbon amount of the starting material powder and the atmosphere during sintering.

If Ni and/or Co is less than 5% by weight, the toughness will be significantly insufficient, and if it exceeds 25% by weight, the wear resistance will be significantly lowered, which is undesirable.
The content is set at 5 to 25% by weight.

The hard phase in the titanium carbide-based sintered alloy for cutting tool parts of the present invention is composed of titanium carbide cores 4a, 5a of the periodic table,
A first cored hard phase surrounded by the outer periphery of a carbonitride solid solution of two or more of Group 6a metals (consisting of the metal elements in the compound used as the starting material), or titanium and Group 6a metal. 4a and 5a of the periodic table.
, a second cored hard phase formed by surrounding the outer periphery of a carbonitride solid solution of two or more of Group 6a metals (consisting of the metal elements in the compound used as the starting material), or 4a of the periodic table. ,
Consisting of a carbonitride solid solution of two or more of group 5a and 6a metals (consisting of the metal elements in the compound used as the starting material), the core of the carbonitride solid solution rich in Ti and N is treated with W or Mo. The third region is surrounded by an outer periphery rich in 6a metal deposits and poor in N.
The cored Koga phase, or the core of titanium carbonitride, is a carbonitride solid solution of two or more metals from groups 4a, sa, and sa of the periodic table (consisting of the metal elements in the compound used as the starting material). The fourth cored hard phase is surrounded by the outer periphery of the titanium nitride, and furthermore, the core of titanium nitride is surrounded by two or more metals from groups 4a, 5a, and Sa of the periodic table (metals in the compound used as the starting material). These include a fifth cored hard phase surrounded by the outer periphery of a carbonitride solid solution (consisting of elements), and other hard phases in which the core and outer periphery have a homogeneous structure. 4a, 5a of the periodic table mentioned here,
The carbonitride solid solution of two or more group 6a metals remains in the non-equilibrium state in the alloy M1 weave, and its specific component structure is, for example, (Ti, W) (C, N).

(Ti, Mo) (C, N).

(Ti, Cr) (C, N) (Ti, W, Mo) (C, N).

(Ti, W, Cr) (C, N).

(Ti, W, Ta) (C, N).

(Ti, W, Mo, Ta) (C, N).

(Ti, W, Ta, Zr) (C, N).

(Ti, W, Mo, Ta, Zr) (C, N) (Ti, W
, Mo, Ta, Nb, Zr) (C, N), and the like.

Titanium carbide, which mainly constitutes the hard phase in the titanium carbide-based sintered alloy for cutting tool parts of the present invention, improves wear resistance, and titanium carbide contains 20 ffr amount%.
If the content is less than 65% by weight, the wear resistance will not be sufficient for practical use as cutting tool parts, and if the content exceeds 65% by weight, the thermal shock resistance will decrease, which is undesirable. The content of titanium carbide is determined to be 20 to 65% by weight.

Titanium nitride, which mainly constitutes the hard phase, cannot strengthen the binder phase if it is less than 18% by weight, and on the other hand, if it is contained in excess of 40 times, it is difficult to sinter and pores are likely to occur. This results in a decrease in wear resistance. Therefore, the amount of titanium nitride to be contained in the sintered alloy is determined to be 18 to 40% by weight.

Carbides of group 6a metals in the periodic table, which mainly constitute the hard phase, cannot strengthen the binder phase if it is less than 15% by weight and have poor defectiveness, and conversely if it is contained in an amount exceeding 40% by weight. , the wear resistance, welding resistance, and oxidation resistance at high temperatures decrease, which is undesirable. Therefore, the carbide of group 6a metal of the periodic table to be included in the sintered alloy is 15 to 40% by weight.
This is what has been established.

In the titanium carbide-based sintered alloy for cutting tool parts of the present invention, in addition to the respective component compositions that constitute the hard phase and the binder phase, the particle size of the hard phase plays a very important role.
If the average particle size of this hard phase is less than 1 gm, the mean free path of the binder phase becomes too small, which reduces the propagation resistance of thermal cracks and reduces thermal shock resistance.On the other hand, if the average particle size of the hard phase exceeds 2 gm, the 8-crack It becomes easier to propagate within the hard phase grains, reducing fracture resistance. Therefore, the average particle size of the hard phase is 1.0 μm.
~2.0gm. In addition, the hard phase with a particle size of 0.5 uLm or less is 10% by volume based on the entire hard phase.
If the amount exceeds 100%, the mean free path of the binder phase becomes small, promoting the propagation of cracks, and reducing thermal shock resistance. On the other hand, in order to suppress the hard phase with a grain size of 0.5 μm or less to less than 1% by volume with respect to the entire hard phase, there is no other way than to actively promote grain growth (Ostwald growth) during sintering. Otherwise, the grain growth of the hard phase will become significant, leading to a decrease in toughness. Therefore.

The hard phase having a particle size of 0.5 Bm or less is determined to be 1 to 9 aM% with respect to the entire hard phase.

When 5 to 31% by weight of the titanium carbide contained in the above-mentioned hard phase is replaced with at least one carbide or nitride of a group 5a metal in the periodic table, crack propagation within the hard phase grains is inhibited and heat resistance is improved. Since it improves impact resistance, it is preferable to perform inspection as necessary. Furthermore, when 0.5 to 8% by weight of titanium carbide contained in the hard phase is replaced with at least one carbide or nitride of Zr or Hf,
Since it improves thermoplastic deformability, it is preferable to replace it as necessary.

When producing the titanium carbide-based sintered alloy for cutting tool parts of the present invention, most of the production processes are based on conventional powder metallurgy methods, but since it is necessary to control the particle size of the hard phase, the starting material Special consideration must be given to the selection of powder particle size, mixing and grinding process, and sintering conditions.

First, among the starting raw material powders, those for forming the core of the cored hard phase and the homogeneous hard phase described above are selected to have as narrow a particle size distribution as possible, and the average particle size is determined later. Considering the mixing and pulverizing process, it is preferable to select particles with a size that is approximately twice the average particle size of the target hard phase (1, for example, an average particle size of 2 to 3 gm). and a part or all of the titanium nitride into a solid solution powder of titanium carbonitride, or one of titanium carbide and tungsten carbide.
It is also possible to use part or all of a solid solution powder of titanium carbide/tungsten as a starting material.Furthermore, carbides of group 6a metals of the periodic table may be 1. For example, if tungsten carbide powder is used as a starting material, part of it may be used as a starting material. By adding tungsten powder and carbon powder as necessary, it is possible to control the value of the lattice constant of the binder phase. The Ni and/or CO powder, which is the main component of the binder phase, should be as fine as possible, for example, with an average particle size of 1 μm or less, or it should be started from easily pulverized nickel oxide and/or cobalt oxide. It can also be used as a raw material powder.

It is preferable to carry out mixing and pulverization in as short a time as possible so as not to increase the amount of fine powder. It is necessary to place importance on the mixing and pulverizing method and time to the extent that the particle size can be said to be determined. In reality, it is preferable to combine the average particle size of the starting material powder and the mixing and pulverizing method, and to study the processing time in advance before determining the conditions for practical use.

Regarding the sintering conditions, it is preferable to perform sintering at a higher temperature or for a longer time than usual in order to reduce fine hard phase particles of 0.57 tm or less. When performing high-temperature sintering, since denitrification occurs when performing normal vacuum sintering, the temperature is first raised to the temperature at which the liquid phase appears in a vacuum or reducing gas atmosphere, and then, after the liquid phase appears, In order to suppress the above-mentioned denitrification, it is preferable to sinter in a nitrogen atmosphere of 1 to 20 torr.

When the sintered alloy obtained by the above method is subjected to hot isostatic pressure (HIP) treatment at a temperature of 1,300°C or higher and a pressure of 1,000 atm or higher in a nitrogen gas or inert gas atmosphere, the strength of the layer at room temperature decreases. This is a good thing.

(Function) The titanium carbide-based sintered alloy for cutting tool parts of the present invention has a binder phase in the grain boundaries of the hard phase, and the titanium carbide forming the hard phase has the effect of improving wear resistance. Titanium carbide acts to promote solid solution of group 6a metals in the periodic table into the binder phase, thereby strengthening the binder phase. Furthermore, by controlling the particle size of the hard phase, the mean free path of the binder phase is prevented from becoming small, thereby improving thermal shock resistance. Furthermore, if necessary, carbides or nitrides of Group 5a metals of the periodic table may be added to the hard phase to improve the strength of the hard phase, prevent crack propagation within the hard phase grains, and improve the strength of the hard phase. The carbide or nitride of Zr or Hf has the effect of improving the thermal shock resistance along with the grain size, and the carbide or nitride of Zr or Hf has the effect of improving the plastic deformation resistance.

(Example) Example 1 Various carbide powders, nitride powders, carbonitride solid solution powders, and carbide powders with an average particle size of 2 to 3 gm and an average particle size of 1
．． Using various starting material powders of Ni and Co of 0μm,
The compositions were blended as shown in Table 1 and mixed and pulverized in a mixing container containing acetone and a cemented carbide pole. The mixing and pulverizing conditions were such that the titanium carbide powder and other powders except the solid solution powder were first mixed for 45 hours, then the titanium carbide powder and/or each solid solution powder were additionally blended, and the mixture was further mixed for 5 hours.

The mixed powder thus obtained was pressed into a predetermined shape to obtain a powder compact.Then, it was heated to 1400°C in a vacuum of 5X 102 torr for 57 days, and after 1400°C, it was placed in a nitrogen atmosphere of 5 torr. In this atmosphere, the temperature was raised to the sintering temperature and held, and sintered to obtain a sintered alloy of the present invention and a comparative sintered alloy. However, in each sample, the lattice constant of the binder phase was controlled by replacing part of WC or MO2C with W and C or MO and C, or by adding only a small amount of carbon powder. °1st
The table shows the compounding composition and sintering conditions of the inventive product and the comparative product. Inventive products (+) to (13) thus obtained and comparative product (
1) - (11) were photographed with a 5000x magnification using a scanning type electronic type A mirror. j! The i rate was calculated. Furthermore, after dissolving and removing the hard phase on the surface of each alloy, the lattice constant of the bonded phase was determined by X-ray diffraction. Furthermore, the transverse rupture strength and sag of each alloy were measured. These results are also listed in Table 2.

The following margin is Example 2 The present invention product and comparative product obtained in Example 1 and commercially available JIS
A cutting test was conducted by continuous turning under the following conditions (a) by adding a cemented carbide equivalent to standard P30, and the average flank wear throughput, crater wear amount, and thermoplastic deformation amount were measured and compared.

In addition, using each sample, a cutting test was conducted by intermittent rolling under the following condition (b), and the time until breakage was compared.

The cutting test results under these conditions (a) and (b) are shown in Table 3.

(a) Conditions (wear resistance and hardness,!!11 plastic deformability) Work material SN0M439 (Hs 230) 250a
+mφ Chip shape 5PGN422 (0, lX-30° linear honing) Cutting speed 160 m/win Cut stitch 1, 5 + W layer feed speed 0, 3 m + m/rev cutting time 3
m1n (dry type) % type %) Chip shape 5PGN422 (0,l ) The following margin (effects of the invention) As a result of the above, the titanium carbide-based sintered alloy for cutting tool parts of the present invention has a higher performance when compared with conventional titanium carbide-based sintered alloys, especially when compared with the same amount of binder phase. Although the wear resistance and thermoplastic deformation resistance are approximately the same, the fracture resistance is 2.3 to 5.8 times better. Furthermore, even if conventional titanium carbide-based sintered alloys were used in the area where cemented carbide is used, they could only be used for a portion of PO5 to PIO according to the JIS standard. Compared to JIS standard P30a hard alloy, titanium-based sintered alloy has the same crater wear resistance and thermoplastic deformation resistance, and the same or about 16% better fracture resistance.
The effect is that the flank wear resistance is approximately twice as good. For these reasons, the titanium carbide-based sintered alloy for cutting tool parts of the present invention is a very useful material for industrial use.

Claims (3)

[Claims] (1) Bonded phase 5 to 2 mainly composed of Ni and/or Co
5% by weight, remaining 20 to 65% by weight of titanium carbide, 18 to 40% by weight of titanium nitride, a hard phase containing 15 to 40% by weight of at least one carbide of group 6a metal of the periodic table, and inevitable impurities. In the sintered alloy, the hard phase has an average grain size of 1.0 μm to 2.0 μm and 0.5 μm.
The hard phase with a particle size of m or less is 1 to 10% by volume of the total hard phase, and the bonded phase has a lattice constant of 3.56 Å to
A titanium carbide-based sintered alloy for cutting tool parts, characterized by having a thickness of 3.61 Å. (2) The hard phase is 5 to 31% by weight of the titanium carbide.
2. The titanium carbide-based sintered alloy for cutting tool parts according to claim 1, wherein the titanium carbide-based sintered alloy contains at least one carbide or nitride of a group 5a metal of the periodic table. (3) The hard phase is characterized in that 0.5 to 8% by weight of the titanium carbide is replaced with at least one carbide or nitride of Zr or Hf. The titanium carbide-based sintered alloy for cutting tool parts according to item 1 or 2.