JPS60106941A - Tough cermet - Google Patents

Abstract

PURPOSE:To provide high-toughness cermet having excellent resistance to plastic deformation and thermal cracking by making an alloy consisting of the dispersion phase composed of WC, TiC, TaC, NbC, Mo2C and TiN and the bond phase such as Ni non-magnetic. CONSTITUTION:An alloy consisting of 5-50wt% WC, 10-60% TiC, 5-30% TaC, 0.5-20% Mo2C and 5-30% TiN as the components for forming a dispersion phase and consisting of 5-20% Ni in addition to unavoidable impurities as a bond phase is formed a solid solution with the bond phase of about 20-25% W so as to make the coercive force of the alloy 0Oe by which the highly wear- resistant high-toughness cermet having excellent resistance to plastic deformation and thermal cracking is obtd. A part or the whole of said TaC can be substed. with NbC. The cutting tool consisting of the above-mentioned cermet has a long life and exhibits stable performance in interrupted cutting and exhibits stable performance under the cutting conditions of high speed and high feed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cermet used as a cutting tool material, and is a tough cermet that has excellent cutting properties, particularly plastic deformation resistance and heat crank resistance, which are the weak points of conventional cermets. This is what we provide.

Conventionally, titanium carbide (hereinafter abbreviated as 'l'ic) 1 and titanium carbide (hereinafter abbreviated as T1CN) dispersed cermets containing titanium nitride have lower thermal conductivity than WCC cemented carbide due to the properties of TiC, which is the main component. Unfortunately, the cutting edge becomes hot, causing plastic deformation and thermal cranking.

In response to this, it has been proposed to increase the heat resistance of the binder phase through precipitation strengthening by adding AI.

There is a drawback that the ductility of the binder phase itself becomes poor and the toughness of the alloy deteriorates. Solid solution strengthening of the binder phase has also been proposed, but conventional methods cannot be said to be perfect because the amount of solid solution of W and Mo is limited.

The present inventors have conducted repeated research to improve the drawbacks of the above-mentioned prior art and to create a strong cerment with improved plastic deformation resistance and heat cracking resistance without deteriorating the toughness of the AT1 alloy (at1 alloy coercive force As shown in Figure 1, there is a correlation with the amount of W dissolved in the binder phase, and when the solid solute WC exceeds 20 (Oe) K, it becomes approximately 0 (Oe) K. Hue
) It has been found that the strength of the alloy at high temperatures is significantly improved by solidly dissolving wl in the binder phase to the extent that wl is dissolved in the binder phase. The reason for this is thought to be that the binder phase undergoes significant solid solution strengthening and plastic deformation of the binder phase, which is the cause of plastic deformation of the alloy at high temperatures, is suppressed. As a result, it was confirmed that the material had excellent plastic deformation resistance even in actual cutting.

In order to achieve a coercive force of 0 to 30 (Oe), which is a feature of the present invention, it is necessary to set the W solid solution amount to 20 to 25 inches, but it is not possible to set the W solid solution amount to 15 to 25 inches. Figure 2 shows what is possible by adjusting the WC composition and ψN ratio of the alloy.

From Figure 2, at CZN ratio 2, the WC content of the alloy is 10%.
As described above, it has been found that when the WC content of the alloy is 25 or more when the N ratio is 3, the W content in the binder phase is 15 or more.

We have also discovered that NbC contributes to the high-temperature properties of the alloy, including its heat resistance and deformability. This is to allow the particles to grow to some extent, to prevent the upward movement of dislocations in the bonded phase, and to increase the deformation resistance of the bonded phase.

When ordinary raw materials are used to increase the amount of W dissolved in the binder phase, even if the WC content is increased, the amount of W solid dissolved in the binder phase does not reach 15 to 25 T. Therefore, in order to stably dissolve more than 15% in solid solution, the above-mentioned L/
In addition to adjusting the N ratio and WC content, the following method must be used. This method contained WC (W'l
The reason for this is that if W is not previously included in the carbonitriding raw material, W will be dissolved in solid solution in the binder phase during cooling. Because there is a large amount of diffused solid solution into carbonitrides,
This is because the amount of W remaining in the bonding phase is reduced.

IBL thermal cracks have not been studied extensively in the past, but by carefully observing the propagation path of thermal cracks, we found that they propagate through the carbide-bond phase interface. Therefore, from the viewpoint that the resistance to thermal crack propagation can be increased by improving the interfacial strength, we studied the relationship with the binder phase composition and obtained the following result.

Since it is difficult to measure the interfacial strength, we measured the wetting angle of the carbide-bond phase, which represents the interfacial strength.
It has been found that (Oe) becomes almost 0' when the amount of iron in the binder phase is 15% or more. This is thought to result in good wettability and high carbide-bonded phase interface strength, making it difficult for thermal cracks to propagate.

It has been discovered that due to the effects of (al and (bl), a cermet can be obtained that has less deterioration in toughness than precipitation type alloys, is less deformable at high temperatures, and has almost no thermal cracks.

Next, the reason for the above-mentioned numerical limitations in the tough cermet of the present invention will be described.

(1) Tungsten carbide If the tungsten carbide content is less than 5%, it is virtually impossible to solidly dissolve 209b to 25% of W in the binder phase, and s
If it exceeds ow, the wear resistance will be significantly deteriorated, and the amount of skeleton will increase and the toughness will also deteriorate, so it was set at 5 to 50%. Among them, 20 to 40 inches seems to be the most desirable.

(2) If the titanium carbide 'l'ic is less than 10%, the desired wear resistance as a cermet cannot be obtained, and if the titanium carbide is more than 60%, it is 1lliC.
Since the lack of toughness of alloy 9 appears in the alloy properties and the toughness of alloy 9 decreases, it was set to 10 to 60 inches. Also 'ri(:ha(1'i, W
) ON (Ti MoW) UN (T i, Ta,
W) Addition of TE in the form of UN is preferred.

(3) Tantalum carbide (Ta e) contributes to improving the high-temperature properties of 0-alloy with a finer grained structure, but carbide particles grow abnormally when the structure is less than 5 mm.
5 to 30% since toughness tends to deteriorate when it is more than 0%.
And so.

(4) When replacing niobium carbide TaC with NbC, as the amount of substitution increases, the high temperature strength of the alloy increases and the plastic deformation resistance improves. However, in general, Nb(,' tends to reduce toughness, but in this research, no major deterioration in toughness was observed even when all of TaC, up to 30 pieces, was replaced with Nbe.
Partial or complete substitution of 1"aC is possible.

(5) Molybdenum carbide Mo2C forms a peripheral structure around the carbide and contributes to improving wettability with the binder phase.

At 0.5% or less, the desired effect is not observed.

In addition, if Mo2C exceeds 20%, the wear resistance of the alloy deteriorates due to the low hardness of Mo2C.

(6) The addition of titanium nitride (TiN) has been shown to improve the high-temperature strength and toughness of the alloy; however, the desired effect is not observed when the content is less than 50%, and when the content exceeds 30%, wetting with the binder phase The thickness was set at 5 to 30 inches to avoid deterioration in performance.

(7) Binding Phase If the binding phase content is less than 5%, the toughness is insufficient, and if it exceeds 20%, the strength at high temperatures will be weakened, so that the desired properties can be obtained as a tough cermet with heat resistance, which is the object of the present invention. Since it is not possible to do so, it was set at 5 to 20 inches. For cutting purposes, 8 to 15% is considered to be particularly desirable.

(8) Coercive force If the coercive force is 30 (Oe) or more, the amount of W dissolved in solid solution in the binder phase is small and the desired carbide-bond phase wettability cannot be obtained, so it was set to 0 to 300e.

Next, the characteristics of the tough cermet of the present invention will be specifically explained using examples.

Example 1 First, (TiW)UN with a C/N atomic ratio of 1 or more, ('l
'iTa W) UN, and (Ti Mo W)
The raw material powder for forming the dispersed phase with the composition of
NO,! (2.04) TiN (1.2μ)
we (1.0μ) MO2C (1.5μ) and Tag (1.4μ) powder in appropriate amounts.

After mixing in a ball mill, react in vacuum at 1,600 to 1,900°C for 2 hours to perform solid solution treatment, and after cooling, use a ball mill to reduce the average particle size to d.
It was adjusted by grinding to 1.0μ.

The raw material powder for forming the binder phase was Ni (1.0μ
) CO (1.0μ) and W (0.5μ) powders were used.

Therefore, regarding the production of the tough cermet of the present invention, the above-mentioned (Ti W)UN (Ti Ta W)UN('l
' i Mo W ) (,: Using a powder that forms a binder phase with at least one type of N, the rest is the above-mentioned W as necessary.
C, 'l'a C, etc. are used alone and blended in a ball mill.') After drying the mixed powder, it is pressed to form a green compact. '
The thermets of the present invention are baked for 1 hour in the vacuum of a wag) 1
-6 were produced. The component compositions of the thermets 1-1 to 1-6 of the present invention are shown in Table 1. Table 1 shows comparative cermets A-B manufactured under the same manufacturing conditions as the cermet of the present invention described above except for changing the alloy composition and binder phase composition.
is marked 0F.

Next, regarding the above-mentioned inventive thermets) 1.2.3.4 and 6 and the above-mentioned inventive thermets) B, C, i) and B, continuous and intermittent cutting and thermal crack comparison cutting tests were conducted under the cutting conditions shown below, and the results were as follows. is also listed.

■Continuous cutting conditions (measurement of sag on cutting edge) Cutting material 8 parts M440 ()ls40) Depth of cut 2.
0- Feed rate 0.7ms/rev Cutting speed 200m/= Cutting time 30 seconds ■ Intermittent cutting conditions Work material aCM440 ()is 40 ) Depth of cut
2. 〇- Cutting speed 100m/sm Cutting time 6 feeds 91- ■Thermal crack Cutting conditions Work material aCM440 (Hs40) Work material shape 5X300X200 Cutting speed 150m/Y feed rate 0.3mm/blade depth of cut 2- Cutting time 15゜As is clear from Table 1, the cermets of the present invention have extremely excellent heat crank resistance and plastic deformation resistance, and no deterioration in toughness is observed.

Example 2 Same raw material powder and average particle size 1 as used in Example 1
．． 5 μ of Ni-AI (Ni: 70%, Al: 3
Comparison cermet 7.8 and cermet 7.8 of the present invention were manufactured using alloy powder and under similar manufacturing conditions. The components of these cermets, the physical properties of the binder phase component 9 alloy,
The same cutting test results as in Example 1 are shown in Table 2. As is clear from Table 2, the cermets of the present invention have plastic deformation resistance comparable to that of the γ' phase precipitated cermets, and are far superior in chipping resistance and heat cracking resistance.

Example 3 Under the same conditions as in Example 1, cermets 9 to 12 of the present invention (comparative cermets) l-K were produced. The composition, binder phase composition, physical properties, and cutting test results of both cermets are shown in Table 3.

As is clear from Table 3, the addition of NbC.

It is recognized that this has a significant effect on the plastic deformation resistance of the alloy at high temperatures.

As mentioned above, the cermet of the present invention has a weak interfacial strength between the charcoal material and the binder phase, is extremely resistant to thermal cracking, and has excellent toughness [which conventional cermets were not good at], so it is extremely effective in interrupted milling cutting where thermal cycles occur. In addition to having a long lifespan.

Shows particularly stable performance in intermittent heavy cutting with large feed rates.

■) It exhibits stable performance under high-speed, high-feed cutting conditions due to its excellent binder phase solid solution strengthening, plastic deformation resistance, and wear resistance.

[Brief explanation of the drawing]

Figure 1 shows the relationship between the degree of Wg dissolved in the binder phase and the coercive force of the alloy, and Figure 2 shows the relationship between the amount of WC in the alloy and the amount of W solid dissolved in the binder phase. It is something. Applicant: Hitachi Choukou Co., Ltd. Procedural amendments to the Commissioner of the Japan Patent Office 1 Handwritten indication Patent Application No. 214799 of 1983 3 Relationship with the nature of the person making the amendments Patent applicant 4 Date of amendment order 1988 February 8th (Shipping date: February 28th, 1982)
5. Symmetry of correction

Claims (2)

[Claims] (1) As dispersed phase forming components, 1 weight ratio of tungsten carbide is 5 to 50%, titanium carbide is 10 to 6i, and tantalum i-ide is 5 to 50%.
30%, molybdenum carbide 0.5-20% titanium nitride 5
~30% as the bonded phase. A tough cermet characterized by having a coercive force of 9 alloys equal to 0 (Oe) in an alloy consisting of 5 to 20% nickel in addition to unavoidable impurities. (2) A tough cermet according to claim 1, characterized in that part or all of the tantalum carbide is replaced with niobium carbide.