JPH0333771B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a nitrogen-containing titanium carbide-based sintered alloy that is suitable for wear-resistant tool parts or cutting tool parts and has excellent strength, wear resistance, and heat deformation resistance. (Prior Art) Generally, titanium carbide has poor affinity with iron group metals and has excellent oxidation resistance compared to tungsten carbide. For these reasons, TiC-based sintered alloys containing TiC as a main component have been put into practical use instead of WC-based sintered alloys, especially for cutting tool parts for cutting ferrous materials. However, TiC-based sintered alloys have a problem of lower strength than WC-based sintered alloys and poor plastic deformation resistance at high temperatures. As a solution to these problems, many nitrogen-containing TiC-based sintered alloys have been proposed. Representative examples of nitrogen-containing TiC-based sintered alloys include JP-A-51-93711 and JP-B-Sho 56-
There is a publication number 51201. (Problems to be Solved by the Invention) JP-A-51-93711 discloses that, in weight percent, tungsten carbide is 10 to 60%, titanium carbide is 5 to 40%, tantalum carbide is 5 to 30%, and titanium nitride is 3 to 20%. %, cobalt, nickel, iron, and other iron group metals by 5 to 20%.
The alloy disclosed in JP-A-51-93711 suppresses the grain growth of solid solution particles and makes fine crystal grains by adding titanium nitride to a composition whose main component is TiC. It has higher hardness and improved wear resistance than base sintered alloys. Furthermore, since titanium nitride has higher thermal shock resistance than titanium carbide, the thermal shock resistance is improved compared to a nitrogen-free TiC-based sintered alloy. However, the alloy disclosed in JP-A-51-93711 has a nucleated structure with titanium carbide as the nucleus, similar to the nitrogen-free TiC-based sintered alloy, so the grain refinement is not remarkable. There is a problem that the plastic deformation resistance at high temperatures is poor. Japanese Patent Publication No. 56-51201 discloses that nitrogen-containing
It is a TiC-based sintered alloy, which is a two-phase mixture consisting of a carbide solid solution rich in titanium and nitrogen and another hard phase rich in Group 6 metal components but poor in nitrogen, and the two-phase mixture forms a microstructure. However, it is characterized in that a carbonitride phase rich in titanium and nitrogen is surrounded by a phase rich in Group 6 metals but poor in nitrogen, forming the main interface with the binder phase alloy. The alloy disclosed in Japanese Patent Publication No. 56-51201 is a nitrogen-free alloy.
Unlike TiC-based sintered alloys, the core is a carbonitride phase rich in titanium and nitrogen, resulting in fine grains. It has excellent characteristics. However, this special public service 56-51201
The alloy disclosed in the publication has a selected composition within the spinodal region and is produced using a spinodal reaction, so it requires manufacturing of the starting raw material powder, the sintering furnace used during sintering, the sintering atmosphere, etc. Unlike the conventional powder metallurgy method, there is a problem in that it cannot be manufactured unless the conditions are controlled very strictly. The present invention solves the above-mentioned problems. Specifically, the present invention has a core made of a carbide containing Ti and W, and this core is surrounded by an outer periphery of carbonitride. The purpose of this invention is to provide a nitrogen-containing titanium carbide-based sintered alloy in which a hard phase with a core structure is formed in a sintered alloy, and which has excellent wear resistance, strength, and heat deformation resistance at high temperatures. (Means for solving the problem) The present inventors added various other carbides to TiC-TiN-Mo ₂ C-Ni alloy, which is the basic system of nitrogen-containing TiC-based sintered alloy. However, when we were considering the role of added carbide, we found that by adding an appropriate amount of tungsten carbide relative to the total amount of titanium nitride and molybdenum carbide, and by controlling the atmosphere during sintering, compared to the addition of other carbides. It was discovered that the alloy structure becomes extremely fine, the high-temperature hardness is improved, the strength is high, and the edge deformation resistance during cutting is excellent. Based on this knowledge, we have completed the present invention. That is, the nitrogen-containing titanium carbide-based sintered alloy of the present invention, which has excellent heat deformation resistance, contains Ni and/or Co.
The hard phase consists of 7 to 34 wt% of titanium nitride, 4 to 24.5 wt% of tungsten carbide, and 4 to 12.5 wt% of molybdenum carbide. , plus 2wt%
A composition consisting of at least one of the following hafnium carbide, 2wt% or less zirconium carbide, 5wt% or less niobium carbide, or 10wt% or less tantalum carbide, and the remainder titanium carbide, and the hard phase is Ti The core of the composite carbide containing Ti, W, Mo, and at least one of Hf, Zr, Nb, and Ta
It contains 0.4 to 7 vol% of the first hard phase surrounded by the outer periphery of composite carbonitride containing seeds (however, the hard phase contains a core of titanium nitride according to the periodic table).
2 of carbides and nitrides of group 4a, 5a, 6a metals
Cases containing 0.5 to 5 vol% of a cored hard phase surrounded by the outer periphery of more than one type of mutual solid solution are excluded. )
It is characterized by this. Specifically, the hard phase in the nitrogen-containing titanium carbide-based sintered alloy with excellent heat deformation resistance of the present invention has a core made of a composite carbide of (Ti, W)C (Ti, W, Mo, M ) (C, N) (hereinafter, M represents at least one of Hf, Zr, Nb, Ta).
It contains 0.4 to 7 vol% of hard phase.
The remaining hard phase, excluding this first hard phase, has a core made of, for example, TiC carbide (Ti, W, Mo,
M) A second hard phase surrounded by an outer peripheral part made of a composite carbonitride of (C, N), a core part made of a composite carbonitride of (Ti, W) (C, N), Mo, M)
A third hard phase surrounded by a composite carbonitride of (C,N), a core made of carbonitride of Ti(C,N), (Ti, W, Mo,
M) A fifth hard phase surrounded by an outer periphery made of a composite carbonitride of (C, N) (however, the fifth hard phase is 0.5~
Excludes cases containing 5vol%. ), etc. In particular, from the viewpoint of easy sinterability and heat deformation resistance of the sintered alloy, it is preferable that the hard phase consists of a first hard phase and a second hard phase. The core portion and the outer peripheral portion constituting these hard phases have a stoichiometric composition or a non-stoichiometric composition. It is particularly preferable that the average particle diameter of the first hard phase contained as the hard phase is from 0.1 to 1.5 μm, since it tends to have excellent strength and heat deformation resistance. Further, the average particle size of the remaining hard phase excluding the first hard phase is preferably 3 μm or less, preferably
When the thickness is 1.0 μm or less, the properties of the sintered alloy tend to be excellent. The binder phase in the nitrogen-containing titanium carbide-based sintered alloy with excellent heat deformation resistance of the present invention is composed of Ni and/or Co, and 0.1% of other elements constituting the hard phase, particularly Mo and C. In some cases, the following impurities are dissolved in solid solution. Next, the reasons for limiting the numerical values in the nitrogen-containing titanium carbide-based sintered alloy with excellent heat deformation resistance of the present invention will be described below. When the binder phase is less than 3 wt%, the hard phase becomes relatively large, exceeding 97 wt%, making sintering difficult. This makes it difficult to obtain a dense and strong alloy. On the other hand, if the binder phase exceeds 18 wt%, the hard phase becomes relatively less than 82 wt%, resulting in a decrease in wear resistance. For this purpose, the content of the binder phase is determined to be 3 to 18 wt%. When titanium nitride in the hard phase is less than 7wt%,
The entire hard phase shows a tendency towards coarse graining, reducing wear resistance. On the other hand, if the amount of titanium nitride exceeds 34 wt%, sintering becomes difficult and it becomes difficult to obtain a dense sintered alloy. For this reason, the content of titanium nitride in the hard phase is determined to be 7 to 34 wt%. When the content of tungsten carbide in the hard phase is less than 4wt%, the first hard phase with (Ti, W)C as the core becomes
When the content is less than 0.4 vol%, the hard phase becomes coarse grained, resulting in a decrease in wear resistance and plastic deformation resistance. Conversely, when the amount of tungsten carbide exceeds 24.5 wt%, tungsten carbide precipitates in the hard phase, inhibits refinement of the hard phase, and reduces strength. For this,
The content of tungsten carbide in the hard phase is determined to be 4 to 24.5 wt%. When molybdenum carbide in the hard phase is less than 4 wt%, sintering becomes difficult and it becomes difficult to obtain a dense sintered alloy. On the other hand, if the amount of molybdenum carbide exceeds 12.5 wt%, the outer periphery forming the hard phase becomes coarse, resulting in a decrease in strength. For this reason, the molybdenum carbide content in the hard phase is determined to be 4 to 12.5 wt%. Hafnium carbide exceeding 2wt% in the hard phase,
If more than 2wt% of zirconium carbide, more than 5wt% of niobium carbide, or more than 10wt% of tantalum carbide is present, the outer periphery becomes thicker, and the hard phase eventually becomes coarser, resulting in a decrease in strength. For this reason, the hard phase contains hafnium carbide at most 2 wt%, zirconium carbide at most 2 wt%, niobium carbide at most 5 wt%, and tantalum carbide at most 10 wt%. When the first hard phase in the hard phase is less than 0.4 vol%, the hard phase becomes coarse grained, and the strength and heat deformation resistance are reduced. On the other hand, if the first hard phase exceeds 7 vol %, tungsten carbide will precipitate, inhibiting the refinement of the hard phase and reducing strength and heat deformation resistance. For this reason, the first hard phase in the hard phase is 0.4 to 7 vol.
%. In order to produce the nitrogen-containing titanium carbide-based sintered alloy with excellent heat deformation resistance of the present invention, starting raw material powder with an average particle size of 3 μm or less is wet-mixed and pulverized in an organic solvent. After molding the pulverized powder using the conventional powder metallurgy molding method, after degreasing as necessary, it is heated to 1400~
It is sufficient to sinter it by holding it at a temperature of 1500°C. especially,
In order to form the first hard phase in the sintered alloy, it is important to minimize the amount of oxygen attached to or dissolved in the green compact after molding, and to increase the amount of oxygen to the point where the liquid phase is generated during sintering. During heating, H ₂ , H ₂ −CO, H ₂ −N ₂ or
It is preferable to create a reduced pressure gas atmosphere of H ₂ -CO-N ₂ and then to create a slightly high vacuum from the generation of the liquid phase to the completion of sintering. (Function) In the nitrogen-containing titanium carbide-based sintered alloy of the present invention, which has excellent heat deformation resistance, the first hard phase acts to make the crystals of the entire hard phase finer, especially in the core part of the first hard phase. The W dissolved in the solid solution functions to make the crystals of the first hard phase fine and also to make the crystals of the entire hard phase fine. Furthermore, at least one of Hf, Zr, Nb, and Ta present in the outer peripheral portion of the hard phase has the effect of improving oxidation resistance, heat deformation resistance, and strength. Due to the interaction between the core in the first hard phase and the composite carbonitride forming the outer periphery of the hard phase, the sintered alloy of the present invention has improved hardness and strength at room and high temperatures. This has the effect of improving the wear resistance, oxidation resistance, and heat deformation resistance. (Example) Example 1 Using WC powder with an average particle size of 1 μm, various carbide powders, nitride powder, Ni powder, and Co powder with an average particle size of 1 to 3 μm as starting materials, each sample in Table 1 was blended. did. Each sample in Table 1 was placed in a hexane solvent using a stainless steel container and a cemented carbide ball.
After mixing for 40 hours, paraffin mixing, drying and
Molding was performed at a pressure of 1 ton/cm ² . Next, the compacted compact was placed in a vacuum furnace to create a vacuum of 1×10 ^-2 Torr, and then
The temperature was raised to 1350° C. in a reduced pressure gas of H ₂ —CO, and then sintered at 1400 to 1500° C. for 1 hour in a vacuum of 5×10 ⁻² Torr. The hardness at room temperature, hardness at 1000° C., and resistance at room temperature of the obtained sintered alloy of the present invention were measured, and the results are shown in Table 2. In addition, the structure of each sintered alloy was observed using an X-ray microanalyzer and a scanning electron microscope, and in particular, the average particle size and content of the first hard phase were determined and are also listed in Table 2. In addition, as a comparative product, the sintering conditions are 5×
Comparative products obtained in the same manner as above except in a vacuum of 10 ^-2 Torr are also listed in Tables 1 and 2.

【table】

[Table] Example 2 Using each sample obtained in Example 1, a cutting test was conducted under the following conditions, and the results are shown in Table 3. Cutting test conditions by turning Work material S48C (CH _B 233) φ250×750 Cutting speed 250m/min Feed rate 0.3mm/rev Depth of cut 1.5mm Cutting time 10min Chip shape SPGN 160308 0.1×(-30°) with honing Dry cutting

【table】

[Table] (Effects of the Invention) As a result, the nitrogen-containing titanium carbide-based sintered alloy of the present invention with excellent heat deformation resistance, the sintered alloy without the first hard phase, and the sintered alloy other than the present invention. Hardness is slightly improved compared to comparative alloys such as bonded metals,
The resistance strength is improved by about 20 to 60%, the amount of flank wear when cutting steel is reduced to about 2/5 to 3/4, and the amount of thermal deformation when cutting steel is reduced to about 1/2 to 1/8. It has the effect of For this reason, the sintered alloy of the present invention can be used in cutting tool parts for turning tool areas and wear-resistant tool parts that are not subjected to much impact force, which are used with conventional titanium carbide-based sintered alloys. Cutting tool parts for areas or high feed areas, cutting tool parts for milling, cutting tool parts for drilling tools such as end mills and drills, cutting tool parts for magnetic tape, paper, metal foil plates, etc., or diamond, CBN, TiC,
It is an industrially useful material that can also be used as a base material for forming coating layers such as TiN and Al ₂ O ₃ .

Claims (1)

[Claims] 1. 3 to 18 wt% binder phase made of Ni and/or Co.
, the remaining hard phase and unavoidable impurities, and the hard phase consists of 7 to 34 wt% titanium nitride and 4 to 24.5 wt% titanium nitride.
of tungsten carbide, 4 to 12.5 wt% of molybdenum carbide, and further 2 wt% or less of hafnium carbide,
A composition consisting of at least one of 2wt% or less zirconium carbide, 5wt% or less niobium carbide, or 10wt% or less tantalum carbide, and the remainder titanium carbide, and the hard phase contains Ti and W. The core of the composite carbide is made of Ti, W, Mo, Hf, Zr,
A first hard phase surrounded by a composite carbonitride containing at least one of Nb and Ta.
Contains 0.4 to 7 vol% (However, in the hard phase,
0.5 to 5 vol.
% is excluded. ) Nitrogen-containing titanium carbide-based sintered alloy with excellent heat deformation resistance. 2 The above hard phase contains 0.4 to 7 vol of the above first hard phase.
% and the remaining titanium carbide core with Ti, W, and Mo.
A second layer surrounded by a composite carbonitride containing at least one of Hf, Zr, Nb, and Ta.
A nitrogen-containing titanium carbide-based sintered alloy having excellent heat deformation resistance as claimed in claim 1, characterized in that the nitrogen-containing titanium carbide-based sintered alloy comprises a hard phase. 3 The first hard phase has an average particle size of 0.1 to 1.5 μm.
A nitrogen-containing titanium carbide-based sintered alloy having excellent heat deformation resistance as claimed in claim 1 or 2.