JPS63286550A - Nitrogen-containing titanium carbide-base alloy having excellent resistance to thermal deformation - Google Patents

Abstract

PURPOSE:To develop a nitrogen-contg. titanium carbide-base sintered alloy as a cutting tool having excellent strength, wear resistance and resistance to thermal deformation by using a sintered material having a hard phase consisting of TiC as well as TiN, WC, Mo2C, and other carbides and bond phase consisting of Co or Ni as a stock. CONSTITUTION:The sintered alloy made of the compsn. contg. 3-18% Co or Ni as the bond phase metal at the time of sintering, having, by weight %, 7-34% TiN, 4-24.5% WC, 4-12.5% Mo2C, and at least one kinds among HfC, ZrC, NbC, and TaC and consisting of the balance TiC as the hard phase of the balance is used as the material for the cutting tools having the excellent resistance to thermal deformation as well as the high hardness and high strength. The hard phase is formed of 0.4-7vol.% the 1st hard layer which is made of (Ti, W)C as its core part, is made of Ti, W, Mo and the double carbonitride of at least one kind among Hf, Zr, Nb and Ta as its coating layer and has 0.1-1.5mum average grain size and the balance the 2nd hard phase consisting of the TiC core part and the coating of Ti, W, Mo, and the double carbonitride of >=1 kinds among Hf, Zr, Nb, and Ta.

Description

Detailed Description of the Invention (Field of Industrial Application) 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. It is.

(Prior Art) In general, titanium carbide has poor affinity with iron group metals and is superior in oxidation properties 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, Tjc2! The i-sintered alloy has a problem in that it has lower strength than the WC-based sintered alloy and also has 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-5B-51.
There is a publication No. 201.

(Problems to be Solved by the Invention) JP-A-51-93711 discloses that 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% by weight. %,cobalt,
This is a cemented carbide for cutting, characterized by comprising 5 to 20% of iron group metals such as nickel and iron. This JP-A-51
The alloy of Publication No. 93711 suppresses the grain growth of solid solution particles to form fine crystal grains by adding titanium nitride to a composition whose main component is TiC, and as a result, a nitrogen-free TiC-based sintered alloy is produced. It has higher hardness and improved wear resistance. In addition, since titanium nitride has higher thermal shock resistance than titanium carbide, nitrogen-free Ti
It has improved thermal shock resistance compared to C-based sintered alloys. 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 of poor plastic deformability at high temperatures.

Japanese Patent Publication No. 5B-51201 discloses that nitrogen-containing Ti
A C-based sintered alloy, it is a two-phase mixture consisting of a carbonitride 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 alloy.

Unlike the nitrogen-free TiC-based sintered alloy, the alloy disclosed in Japanese Patent Publication No. 5B-51201 has fine crystal grains because it has a carbonitride phase rich in titanium and nitrogen as its core. Therefore, the alloy has excellent properties such as wear resistance, strength, and heat deformation resistance. However, since the alloy disclosed in Japanese Patent Publication No. 56-51201 has a selected composition within the spinodal region and is produced using the Subinodal reaction, the starting material powder, the sintering agent used during sintering Unlike the conventional powder metallurgy method, there is a problem in that production cannot be performed without extremely strict control of manufacturing conditions such as the furnace and sintering atmosphere.

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 the present 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 9 strength and heat deformation resistance at high temperatures.

(Means for solving the problem) The inventors added various other carbides to a TiC-TiN-MO2C-Ni alloy, which is the basic system of a nitrogen-containing TiC-based sintered alloy. While considering the role of the added carbide, in particular, adding an appropriate amount of tungsten carbide to the total amount of titanium nitride and molybdenum carbide,
The knowledge that by controlling the atmosphere during sintering, the alloy structure becomes significantly finer than when low-order compounds are added, and that high-temperature hardness is improved, resulting in high strength and excellent resistance to edge deformation during cutting. This is what I got. 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, consists of a binder phase of 3 to 18 wt% of Ni and/or Co, and the remaining hard phase and unavoidable impurities. 7-34 vt% titanium nitride and 4-24
．． 5 wt% tungsten carbide, 4 to 12.5 wt% molybdenum carbide, and at least one of 2 wt% or less hafnium carbide, 2 wt% or less zirconium carbide, 5 wt% or less niobium carbide, or 10 wt% or less tantalum carbide. The core of the composite carbide, which has a composition consisting of a seed and the remaining titanium carbide, and the hard phase contains Ti and W, is combined with Ti, W, Mo, and Hf*Zr*Nb,T
0.4 to 7 maon% of the first hard phase surrounded by the outer periphery of a composite carbonitride containing at least one of a.
It is characterized by containing.

Specifically, the hard phase in the nitrogen-containing titanium carbide-based sintered alloy with excellent heat deformation resistance of the present invention includes (Ti, W
) A core made of a composite carbide of (Ti, W, Mo,
M) Composite carbonitride of (C, N) (hereinafter, M is Hf, Zr
, Nb, and Ta), which is surrounded by an outer peripheral portion, and contains 0.4 to 7 vol% of the first hard phase. The remaining hard phase except for this first hard phase has a core made of, for example, TiC carbide (Ti
, W, Mo, M) (C, N), a second hard phase surrounded by a composite carbonitride of (Ti, W) (C,
A core made of composite carbonitride of (Ti, W, Mo
. M) The fourth hard phase surrounded by the outer periphery made of composite carbonitride of (C, N), or the core made of nitride of TiN, of (Ti, W, Mo, M) (C, N) Examples include a fifth hard phase surrounded by an outer peripheral portion made of composite carbonitride. 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 and outer peripheral portions constituting these hard phases have a stoichiometric or non-stoichiometric composition. If the average particle size of the first hard phase contained as this hard phase is 0.1 to 1.57 zm, it tends to have excellent strength and heat deformation resistance.
This is particularly preferred. In addition, excluding the first hard phase,
The average particle size of the remaining hard phase is 3 pm or less, preferably 1.
If it is 0 Bm 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 the other elements constituting the hard phase, particularly MO and C, are 0. In some cases, impurities of 1% or less 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 relatively hard phase becomes 97%.
Since the amount exceeds wt%, it becomes difficult to sinter. This makes it difficult to obtain a dense and strong alloy. On the other hand, when the binder phase is increased to more than 18 wt%, the wear resistance is relatively lowered to 82 wt% or less than 2 wt% of the hard phase. For this purpose, the amount of the binder phase is determined to be 3 to 18 wt%.

When the content of titanium nitride in the hard phase is less than 7 wt%, the entire hard phase tends to become coarse grained, resulting in decreased 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 tungsten carbide in the hard phase becomes less than 4 wt%,
The first hard phase with (Ti, W)C as the core is 0.4 Maaf
If it becomes less than L%, the hard phase becomes coarse grained, resulting in a decrease in wear resistance and plastic deformation resistance. Conversely, tungsten carbide is 2
When the amount exceeds 4.5 wt%, tungsten carbide precipitates in the hard phase, inhibits refinement of the hard phase, and reduces strength. For this reason, the amount 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 and the strength decreases by 1. For this reason, molybdenum carbide in the hard phase is determined to be 4 to 12.5 wt%.

More than 2 wt% hafnium carbide in the hard phase.

If zirconium carbide exceeds 2 wt%, niobium carbide exceeds 5 wt%, or tantalum carbide exceeds 10 wt%, the outer periphery becomes thicker, and the hard phase eventually becomes coarser, resulting in a decrease in strength. For this purpose, the hard phase contains hafnium carbide 2wt% or less, zirconium carbide 2wt% or less,
Niobium carbide is set at 5 wt% or less, and tantalum carbide is set at 10 wt% or less.

The first hard phase in the hard phase is 0.4 mao! ; When it is less than L%, 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 maan%, tungsten carbide will precipitate, inhibiting the refinement of the hard phase and reducing the strength and heat deformation resistance. For this reason, the first hard phase in the hard phase is determined to be 0.4 to 7%.

In order to produce the nitrogen-containing titanium carbide-based sintered alloy of the present invention with excellent heat deformation resistance, the starting material powder must have an average particle size of 31
After wet-mixing and pulverizing the mixed pulverized powder in an organic solvent using Lm or less, molding the mixed pulverized powder using a conventional molding method in powder metallurgy, and after degreasing if necessary, the Sintering can be carried out by holding at a temperature of °C.

In particular, 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 prevent the generation of the liquid phase during sintering. N2 + H2Co during heating.

It is preferable to create a reduced pressure gas atmosphere of N2-N2 or N2-Co-N2, 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. (Example) Example 1 WC powder with an average particle size of 1 pm, various carbide powders with an average particle size of 1 to 3 pm, and nitriding. Each sample in Table 1 was formulated using Co powder, Nl powder, and Co powder as starting materials. Each sample in Table 1 was mixed in a hexane solvent using a stainless steel container and a cemented carbide ball for 40 hours, mixed with paraffin, dried, and molded at a pressure of 1 ton/c+s2. Place the body in a vacuum furnace and
After creating a vacuum of 1 O-2 Tarr, the temperature was raised to 1350 °C in a reduced pressure gas of N2-Co, and then 5 X 10-
Sintering was carried out at 1400 to 1500° C. for 1 hour in a vacuum of 2 Torr. The hardness at room temperature, the hardness at 1000° C., and the transverse rupture strength at room temperature of the obtained sintered alloy of the present invention were measured, and the results are shown in Table 2. Also, each sintered alloy is
The structure was observed using a line microanalyzer and a scanning electronic Ill microscope, and in particular, the average particle size and content of the first hard phase were determined and are also listed in Table 2.

As a comparative product, the sintering conditions were 5 x 10-2 Tar.
Comparative products obtained in the same manner as above except for being in a vacuum of r are also listed in Tables 1 and 2.

Margin Example 2 Cutting tests were conducted under the following conditions using each sample obtained in Example 1, and the results are shown in Table 3.

Cutting test conditions by turning Work material 348C (CHe 233)
φ250X750 Cutting speed 250 m/win Feed rate 0.3 mm/rev Depth of cut 1.5 mm Cutting time 10 sin Chip shape 5PGN 160308 0, I ) Results 1 The nitrogen-containing titanium carbide-based sintered alloy of the present invention with excellent thermal deformability is superior to comparative alloys such as sintered alloys without the first hard phase and sintered alloys other than the present invention. Hardness is slightly improved compared to
Improved flank wear amount when cutting steel, approximately 215 ~
The amount of thermal deformation when cutting steel is reduced by about 1/2.
This has the effect of reducing the number to ~178.

For this reason, the sintered alloy of the present invention can be used for 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, as well as for higher speed cutting tools. 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.

It is an industrially useful material that can also be used as a base material for forming coating layers such as Tic, TiN, and Al103.

Claims (3)

[Claims] (1) 3 to 18 wt% binding phase made of Ni and/or Co
The hard phase consists of 7 to 34 wt% titanium nitride, 4 to 24.5 wt% tungsten carbide, 4 to 12.5 wt% molybdenum carbide, and 2 wt% or less of molybdenum carbide. The composition is composed of at least one of hafnium carbide, 2 wt% or less of zirconium carbide, 5 wt% or less of niobium carbide, or 10 wt% or less of tantalum carbide, and the remainder is titanium carbide, and the hard phase is composed of Ti and W. The core of the composite carbide containing Ti and W
and a first compound surrounded by an outer periphery of a composite carbonitride containing Mo and at least one of Hf, Zr, Nb, and Ta.
A nitrogen-containing titanium carbide-based sintered alloy having excellent heat deformation resistance and containing 0.4 to 7 vol% of a hard phase. (2) The hard phase has a volume of 0.4 to 7 vo of the first hard phase.
1%, and the remaining titanium carbide core is Ti, W, Mo, and Hf.
, a second hard phase surrounded by a composite carbonitride containing at least one of Zr, Nb, and Ta. Nitrogen-containing titanium carbide-based sintered alloy with excellent deformability. (3) The first hard phase has an average particle size of 0.1 to 1.5μ
A nitrogen-containing titanium carbide-based sintered alloy having excellent heat deformation resistance as claimed in claim 1 or 2, characterized in that m.