JPH0450373B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention provides thermal shock resistance, abrasion resistance, thermoplastic deformation resistance, and high-temperature This invention relates to a titanium carbide-based sintered alloy for cutting tool parts that has excellent fracture resistance. (Prior art) As for titanium carbide-based sintered alloys, carbide-based alloys represented by TiC-Mo ₂ C-Ni-based sintered alloys were first introduced, but compared to tungsten carbide-based sintered alloys, However, 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,
Nitrogen-containing titanium carbide-based sintered alloys have achieved improved thermoplastic deformation resistance and fracture resistance. Many nitrogen-containing titanium carbide-based sintered alloys have been proposed, and among them, for example, Japanese Patent Laid-Open No. 119205/1983 discloses a material for hot rolling equipment parts, and a patent discloses a material for wear resistance. Japanese Patent Application Publication No. 1983
-2860, generally TiN or Ti(C,
The grain growth suppressing effect of N) is used to make the hard phase finer and increase the strength. In particular, nitrogen-containing titanium carbide sintered alloys for cutting tool parts have an average grain size of 1-2 μm starting material powder was mixed and ground and added as a nitrogen source.
Due to the grain growth suppressing effect of TiN or Ti (C, Z),
After sintering, the average grain size of the hard phase is 1 μm or less. 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, and a representative example is JP-A No. 50-102508. There is a public notice. (Problems to be Solved by the Invention) JP-A-50-102508 discloses a titanium nitride containing 5 to 40% of the total amount of titanium carbide and titanium nitride, and consisting of W, Mo, Ta and Nb. The alloy contains 15 to 40% carbide of at least one selected from the group, is bonded with 3 to 30% of iron group metal, and most of the carbide or nitride crystals in the alloy have a grain size of 1 μm or less. A featured bonding alloy is disclosed. 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. Under conditions where impact is applied, there is a problem that the lifespan is shortened due to defects caused by thermal cracks, making it impossible to put it into practical use. The present invention shows that the improvement of the properties of titanium carbide-based sintered alloys for cutting tool parts has conventionally been carried out based on increasing the nitrogen content of the alloy and thereby refining the hard phase. Although it was not possible to obtain performance comparable to that of hard alloys, by increasing the nitrogen content, controlling the hard phase particle size to a relatively coarse grain side, and further strengthening the binder phase, the above-mentioned This problem has been solved, and specifically, 18 to 40% by weight of titanium nitride as a nitrogen source is used.
The average particle size of the hard phase contained is between 1.0 μm and 2.0 μm,
and the hard phase with a particle size of 0.5μm or less is 1 of the total hard phase.
The purpose of the present invention is to provide a sintered alloy that has significantly improved impact resistance, abrasion resistance, and thermoplastic deformation resistance at a concentration of ~10% by volume, and that can be used in the range of use of cemented carbide. (Means for Solving the Problems) The present inventors have found that in order to improve the thermal shock resistance and thermoplastic deformation resistance of a nitrogen-containing titanium carbide-based sintered alloy, the grain size of the hard phase is coarsened to a certain 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 increasing the mean free path of the bonded phase using the method described above does improve heat resistance. Although the impact resistance improved, this time the thermoplastic deformation resistance decreased, causing a problem of causing defects due to thermoplastic deformation. Therefore, we divided the nitrogen-containing titanium carbide-based sintered alloy into both the hard phase and the binder phase, and studied each of them, resulting in the following findings (1) to (4). (1) In order to improve thermal shock resistance, it is necessary to increase the amount of binder phase. It is essential to enhance the high temperature strength of the phase. To achieve this, the nitrogen content in the sintered alloy should be at least 18% in terms of TiN, and the carbide of group 6a metal in the periodic table should be at least 15%, and the lattice constant of the bonding phase should be 3.56 Å to 3.61 Å.
When the bonding phase of the titanium carbide-based sintered alloy is made to have a high temperature strength, the high-temperature strength becomes significantly superior. (2) By controlling the particle size of the starting raw material powder and the manufacturing conditions from mixing and pulverization to sintering conditions, the average particle size of the hard phase of the sintered alloy is set to 1.0 μm to 2.0 μm,
In addition, when the hard phase with a particle size of 0.5 μm or less is 1 to 10% by volume of the total hard phase, the rate of thermal crack propagation of the nitrogen-containing titanium carbide sintered alloy is slowed down and the thermal shock resistance is significantly improved. thing. (3) A part of titanium carbide is added to the periodic table excluding Ti.
When substituted with a carbide or nitride of a group 4a metal, the nitrogen-containing titanium carbide-based sintered alloy has further improved thermoplastic deformation resistance. (4) When a portion of titanium carbide is replaced with a carbide or nitride of a group 5a metal in the periodic table, the thermal shock resistance of a 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 has a binder phase 5 to 5 containing Ni and/or Co as main components.
25% by weight, remaining titanium carbide 20 to 65% by weight, titanium nitride 18 to 40% by weight, a total of 15 to 40% by weight of tungsten carbide and molybdenum carbide, and/or a hard phase consisting of a mutual solid solution of two or more of these. A sintered alloy consisting of inevitable impurities, the hard phase has an average grain size of 1.0 μm to 2.0 μm, and the hard phase with a grain size of 0.5 μm or less accounts for 1 to 10% by volume of the total hard phase. , and the atomic ratio of W and Mo in the hard phase is W:Mo=48.4~
70.0:51.6~30.0, and the lattice constant of the bonded phase is
It is characterized by having a thickness of 3.56 Å to 3.61 Å. 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 contains other hard phases such as 4a of the periodic table,
At least one of group 5a and 6a metals, nitrogen, and carbon is solid-dissolved in Ni and/or Co, and plays a role in strengthening the binder phase. The amount of solid solution in Ni and/or Co increases, and the thermoplastic deformation resistance is significantly improved. If the lattice constant of the bonded phase is between 3.56 Å and 3.61 Å, which represents the total amount of solute atoms solidly dissolved in the bonded phase containing Ni and/or Co as the main component, the defect resistance will be improved. It also has excellent thermoplastic deformability. 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 not preferable. Therefore, the content of Ni and/or Co 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 consists of a titanium carbide core made of two or more metals from groups 4a, 5a, and 6a of the periodic table (in the compound used as the starting material). A first cored hard phase surrounded by the outer periphery of a carbonitride solid solution of metal elements), or a core of a carbide of titanium and at least one group 6a metal of the periodic table 4a, 5a, A second cored hard phase formed by surrounding the outer periphery of a carbonitride solid solution of two or more types of Group 6a metals (consisting of the metal elements in the compound used as the starting material), or a second cored hard phase of the periodic table.
Consisting of a carbonitride solid solution of two or more metals of groups 4a, 5a, and 6a (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 The third cored hard phase is formed by surrounding Mo with a periphery rich in group 6a metals and poor in N, or the core of titanium carbonitride is combined with two or more metals from groups 4a, 5a, and 6a of the periodic table ( The fourth cored hard phase surrounded by the outer periphery of the carbonitride solid solution (consisting of the metal element in the compound used as the starting material), and the core of titanium nitride in the form of 4a, 5a, and 6a of the periodic table. A fifth cored hard phase surrounded by the outer periphery of a carbonitride solid solution of two or more types of group metals (consisting of metal elements with the compound used as the starting material); This includes a hard phase with a homogeneous structure. The carbonitride solid solution of two or more metals of groups 4a, 5a, and 6a of the periodic table described here remains in the alloy structure in a non-equilibrium state, 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), ( Examples include Ti, W, Mo, Ta, Zr) (C, N) (Ti, W, Mo, Ta, Nb, Zr) (C, N). 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 if titanium carbide is less than 20% by weight, it is not practical for cutting tool parts. On the other hand, if the content exceeds 65% by weight, the thermal shock resistance will decrease, which is not preferable. Therefore, the content of titanium carbide in the sintered alloy is determined to be 20 to 65% by weight. Titanium nitride, which mainly constitutes the hard phase, is
If it is less than 18% by weight, strengthening of the binder phase cannot be achieved;
On the other hand, if the content exceeds 40, sintering is difficult and pores are likely to occur, resulting in a decrease in wear resistance. Therefore, the titanium nitride contained in the sintered alloy is 18
~40% by weight. The total carbide content of tungsten carbide and molybdenum carbide, which mainly constitute the hard phase, is 15% by weight.
If the content is less than 40% by weight, the binder phase cannot be strengthened and chipping resistance is poor, and if the content exceeds 40% by weight, the abrasion resistance, welding resistance and oxidation resistance at high temperatures are undesirably reduced. Therefore, the total amount of carbides of tungsten carbide and molybdenum carbide contained in the sintered alloy is set at 15 to 40% by weight. Mo contained in the hard phase and making up the hard phase
When the atomic ratio of Mo/W+Mo>51.6%, the hard phase becomes significantly coarse grained and has low hardness;
If W + Mo < 30.0%, lower carbide (η phase)
Alternatively, free carbon is likely to be generated, making adjustment during sintering difficult. 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. The average particle size of the hard phase is
If it is less than 1 μm, 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 it exceeds 2 μm, thermal cracks tend to propagate within the hard phase grains. This results in a decrease in fracture resistance. Therefore, the average particle size of the hard phase is 1.0 μm.
It is determined to be ~2.0 μm. In addition, the hard phase with a particle size of 0.5 μm or less is 10% by volume of the entire hard phase.
If it exists in excess of , the mean free path of the binder phase becomes small, promoting the propagation of thermal cracks and reducing thermal shock resistance. Conversely, for the entire hard phase,
In order to suppress the hard phase with a grain size of 0.5 μm or less to less than 1% by volume, there is no other way than to actively promote grain growth (Ostwald growth) during sintering, which causes significant grain growth of the hard phase. If this happens, the grain growth of the hard phase will become significant, leading to a decrease in toughness. Therefore, the amount of the hard phase having a particle size of 0.5 μm or less is determined to be 1 to 10% by volume based on the entire hard phase. 5~ of titanium carbide contained in the above-mentioned hard phase
If 31% by weight is replaced with at least one carbide or nitride of group 5a metal in the periodic table, crack propagation within the hard phase grains will be inhibited and thermal shock resistance will be improved, so substitution should be made as necessary. is preferable. In addition, if 0.5 to 8% by weight of the titanium carbide contained in the hard phase is replaced with at least one of Zr or Hf carbide or nitride, the thermoplastic deformation resistance will be improved, so it may be replaced as necessary. is preferable. When manufacturing the titanium carbide-based sintered alloy for cutting tool parts of the present invention, most of the manufacturing 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 powder Special consideration needs to be given to the selection of 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 that the particle size is about twice the average particle size of the target hard phase, for example, the average particle size is 2 to 2.
It is best to select one with a diameter of 3 μm. Further, a solid solution powder of titanium carbide and titanium nitride (part or all of titanium carbide and titanium nitride), or a solid solution powder of titanium carbide and tungsten (part or all of titanium carbide and tungsten carbide) may be used as the starting material. Furthermore, carbides of group 6a metals of the periodic table are
For example, when tungsten carbide powder is used as a starting material, it is possible to control the value of the lattice constant of the binder phase by adding a part of it as tungsten powder and carbon powder as necessary. 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.
The following may be used, or easily pulverizable nickel oxide and/or cobalt oxide may be used as the starting 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. Once the particle size has been determined, it is necessary to place great importance on the mixing and crushing method and time. In reality, it is preferable to combine the average particle diameter of the starting raw material powder and the mixing and pulverizing method, and to determine the practical conditions after considering the processing time in advance. Regarding the sintering conditions, in order to reduce fine hard phase particles of 0.5 μm or less, it is preferable to perform sintering at a higher temperature or for a longer time than usual. 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 appearance of the liquid phase, in order to suppress the above-mentioned denitrification,
It is preferable to sinter in a nitrogen atmosphere of 20 torr. The sintered alloy obtained by the above method is heated at a temperature of 1300℃ or higher for 1000℃ in a nitrogen gas or inert gas atmosphere.
It is preferable to perform hot isostatic pressure (HIP) treatment at a pressure higher than atmospheric pressure, as this further improves the strength at room temperature. (Function) The titanium carbide-based sintered alloy for cutting tool parts of the present invention has a binder phase at the grain boundaries of the hard phase, and the titanium carbide forming the hard phase has the effect of improving wear resistance. , titanium nitride promotes the 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 to be included in the hard phase improve the strength of the hard phase, prevent crack propagation within the hard phase grains, and increase the grain size of the hard phase. Zr or Hf carbide or nitride also works to improve thermal shock resistance. (Example) Example 1 Various carbide powders with an average particle size of 2 to 3 μm,
Nitride powder, carbonitride solid solution powder, carbide powder and metal W, metal Mo, carbon powder and average particle size
Using various starting material powders of 1.0 μm Ni and Co,
The compositions shown in Table 1 were mixed and ground in a mixing container containing acetone and cemented carbide balls. The mixing and grinding conditions were as follows: titanium carbide powder and other powders except solid solution powder were first mixed for 45 hours, and then
Titanium carbide powder and/or each solid solution powder was additionally blended and mixed for further 5 hours. The mixed powder thus obtained was pressed into a predetermined shape to obtain a powder compact. Next, the temperature was raised to 1400°C in a vacuum of 5 × 10 ^-2 torr, 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 all the samples, the lattice constant of the binder phase was controlled by substituting a part of WC or Mo ₂ C with metal W or metal Mo, or by adding a small amount of carbon powder. Table 1 shows the compounding composition and sintering conditions of the inventive product and the comparative product. Each of the samples in Table 1 was made mainly by controlling the amount of carbon.
The lattice constant of the binder phase of the sintered body is controlled, and specifically, the comparative product No. 10 and
Comparative product No. 3 in Table 1 was produced by producing Comparative product No. 11 and further reducing the amount of carbon compared to the product of the present invention in Table 1. The compositional components of the sintered alloys of the present invention products (1) to (10) and comparative products (1) to (11) thus obtained, and the W and Mo contained in the hard phase of the sintered alloys.
The atomic ratios were determined and shown in Table 2-1. Then,
A photograph of each sintered alloy was taken with a scanning electron microscope magnified 5000 times, and the average particle size of the hard phase and the volume fraction of the hard phase with a particle size of 0.5 μm or less present in the hard phase were determined. 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 anti-destructive strength and stiffness of each alloy were measured. These results are also listed in Table 2-2.

【table】

【table】

【table】

[Table] Example 2 The inventive product and comparative product obtained in Example 1 and the commercially available
Adding cemented carbide equivalent to JIS standard P30, the following (a)
A cutting test was conducted under continuous turning conditions, and the average flank wear amount, crater wear amount, and thermoplastic deformation amount were measured and compared. In addition, using each sample, a cutting test was conducted by interrupted cutting under the condition (b) below.
The time until loss was compared. The cutting test results under these conditions (a) and (b) are shown in Table 3. (a) Conditions (wear resistance and thermoplastic deformation resistance) Work material SNCM439 (H _B 230) 250mmφ Chip shape SPGN422 (0.1×30° linear honing) Cutting speed 160m/min Depth of cut 1.5mm Feed rate 0.3mm/ rev Cutting time 3min (dry) (b) Conditions (fracture resistance) Work material SCM440 (H _B 280) 50×150 square wood chip shape SPGN422 (0.1×−30° linear honing) Cutting speed 160m/min Depth of cut 1.5mm feed rate
0.14mm/blade (single blade, dry type, center shaving)

[Table] * This is a defect caused by thermal cracking.
(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 better wear resistance than conventional titanium carbide-based sintered alloys, especially when compared with the same amount of binder phase. Although the hardness and thermoplastic deformation resistance are almost the same, the fracture resistance is 2.3 to 5.8 times better. In addition, conventional titanium carbide-based sintered alloys could only be used in parts of P05 to P10 of the JIS standard even if they were used in the area where cemented carbide is used, but the titanium carbide of the present invention for cutting tool parts Compared to JIS standard P30 cemented carbide, the sintered alloy is
Crater wear resistance and thermoplastic deformation resistance are equivalent,
Fracture resistance is the same or about 16% better,
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 an industrially very useful material.

Claims (1)

[Claims] 1 Binding phase mainly composed of Ni and/or Co 5 -
25% by weight, remaining titanium carbide 20 to 65% by weight, titanium nitride 18 to 40% by weight, a total of 15 to 40% by weight of tungsten carbide and molybdenum carbide, and/or a hard phase consisting of a mutual solid solution of two or more of these. A sintered alloy consisting of inevitable impurities, the hard phase has an average grain size of 1.0 μm to 2.0 μm, and the hard phase with a grain size of 0.5 μm or less accounts for 1 to 10% by volume of the total hard phase. , and the atomic ratio of W and Mo in the hard phase is W:Mo=48.4 ~
70.0:51.6~30.0, and the lattice constant of the bonded phase is
A titanium carbide-based sintered alloy for cutting tool parts, characterized by a thickness of 3.56 Å to 5.61 Å. 2 Binding phase 5 containing Ni and/or Co as a main component
25% by weight, remaining 5-31% by weight of at least one carbide or nitride of group 5a metal of the periodic table, and remaining titanium carbide, totaling 20-65% by weight, titanium nitride 18
~40% by weight, a total of 15 to 40% by weight of tungsten carbide and molybdenum carbide, and/or a hard phase that is a mutual solid solution of two or more of these, and inevitable impurities, the hard phase comprising: The average particle size is
The hard phase with a particle size of 1.0 μm to 2.0 μm and 0.5 μm or less accounts for 1 to 10% by volume of the total hard phase, and the atomic ratio of W and Mo in the hard phase is W:Mo = 48.4 to 70.0: 51.6
~30.0, and the lattice constant of the bonded phase is ~3.65Å
A titanium carbide-based sintered alloy for cutting tool parts, characterized by a thickness of 3.61Å. 3 Binding phase 5 containing Ni and/or Co as a main component
25% by weight, remaining 0.5 to 8% by weight of at least one type of carbide or nitride of Zr or Hf, and remaining titanium carbide, 20 to 65% by weight, 18 to 18% titanium nitride.
40% by weight, a total of 15 to 40% by weight of tungsten carbide and molybdenum carbide, and/or a mutual solution of two or more of these, and an unavoidable impurity. particle size
The hard phase with a particle size of 1.0 μm to 2.0 μm and 0.5 μm or less accounts for 1 to 10% by volume of the total hard phase, and the atomic ratio of W and Mo in the hard phase is W:Mo = 48.4 to 70.0: 51.6
~30.0, and the bonded phase has a lattice constant of ~3.56Å
A titanium carbide-based sintered alloy for cutting tool parts, characterized by a thickness of 3.61Å. 4 Binding phase mainly composed of Ni and/or Co 5 ~
Zr or
At least one carbide or nitride of Hf 0.5
~8% by weight and the remainder titanium carbide, totaling 20-65% by weight, titanium nitride 18-40% by weight, tungsten carbide and molybdenum carbide totaling 15-40% by weight, and/or a mutual solid solution of two or more of these. A sintered alloy consisting of a hard phase and unavoidable impurities, the hard phase has an average grain size of 1.0 μm to 2.0 μm, and the hard phase with a grain size of 0.5 μm or less accounts for 1 to 10 volumes of the total hard phase. %, and the atomic ratio of W and Mo in the hard phase is W:Mo
A titanium carbide-based sintered alloy for cutting tool parts, characterized in that the bonding phase has a lattice constant of 3.56 Å to 3.61 Å.