JPS60106938A - Tough cermet - Google Patents

Abstract

PURPOSE:To obtain the titled cermet having superior resistance to plastic deformation and hot cracking by forming a solid solution of a specified amount of W in the binding phase of an alloy having a specified composition consisting of WC, TiC, TaC, Mo2C and TiN as components forming a dispersed phase and of an iron group metal as the binding phase. CONSTITUTION:An alloy is composed of, by weight, 15-50% WC, 10-60% TiC, 5-30% TaC, 0.5-20% Mo2C and 5-30% TiN as components forming a dispersed phase and of 5-20% iron group metal such as Fe, Co or Ni as a binding phase, and 20-25% W with inevitable impurities is formed a solid solution in the binding phase to obtain tough and hard cermet having improved resistance to plastic deformation and hot cracking without deteriorating the toughness of the alloy.

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 crack resistance, which are the weak points of conventional cermets. This is what we provide.

Conventionally, titanium carbide (hereinafter referred to as T1CN) dispersed cermet, which includes titanium carbide (hereinafter referred to as TiC) and titanium nitride, has poor thermal conductivity compared to WCC cemented carbide due to the properties of its main component, TiC, and has a sharp cutting edge. It has the drawback of being prone to plastic deformation and thermal cracks due to high temperatures.

In response to this, it has been proposed to increase the heat resistance of the binder phase by 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 has also been proposed, but the conventional method is 7, M
The amount of I/'a in solid solution is limited and it cannot be said to be perfect. As a result of repeated research to obtain a cermet with improved toughness (at, the amount of solid solution in the binder phase has a strong correlation with the WC content of the alloy, and as the WC content increases).

As shown in FIG. 1, it was found that the amount of solid solution increased up to 25%. Further, FIG. 2 shows the relationship between the amount of W dissolved in the binder phase and the high temperature creep deformation resistance of one alloy.

This is the result obtained under the conditions of cuff 2/d at a temperature of 1000° C., and the vertical axis represents the time until breakage. The longer it takes to break, the more difficult it is to deform at high temperatures. As shown in FIG. 2, when the amount of solid solution exceeds 10%, the high temperature creep deformation resistance is improved, and especially when the solid solution amount is 20% or more, the high temperature creep deformation resistance increases significantly. As a result, it was found that the material was difficult to deform even during actual cutting, and the plastic deformation resistance was significantly improved. It is also shown in FIG. 1 that it is possible to set the W solid solution amount to 20 to 25 inches by adjusting the WC composition and CZN ratio of the alloy. When the C/N ratio is 2, the WC content of one alloy is 13%.
With the above, the solid solution amount of W in the binder phase exceeds 20%, and in the case of a C/N ratio of 3, the amount of W solid solution in the binder phase exceeds 20% when the WC is 828 qb or more.

In this case, 1. If normal raw materials are used.

Even if the WC content is increased, the amount of W dissolved in the binder phase is 25
% is not reached. Therefore, in order to stably form a solid solution in an amount exceeding 20%, in addition to adjusting the CZN ratio and WC content described above, the following nine methods must be used. This method consists of WC-containing (W+Ti)CN, (W, T
The reason for this is that if the carbonitriding raw material does not contain W in advance, the W dissolved in the binder phase will diffuse and solidify into the carbonitride during cooling. This is because the amount of W that remains in the binder phase decreases due to the large amount of W that is dissolved.

In this way, another characteristic that was observed when the amount of W solid solution in the bonded phase was increased to 20% or more is that in the case of +N+ bonded phase, the coercive force becomes O~30 (Oe) and it becomes almost non-magnetic. That's true. Therefore, within the scope of the present invention, in the case of a Ni bonded phase, the coercive force is 0 to 30 (Oe).

IBL thermal cracks have not been studied much in the past, but by carefully observing the propagation path of thermal cracks, we found that they propagate through the carbide-bond phase interface. Based on 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 results.

Since it is difficult to measure the interfacial strength, we measured the wetting angle of the carbide-bond phase, which represents the interfacial strength, and found that it becomes almost 0° when the amount of W in the binder phase is 20 inches or more.

Therefore, when the solid solution amount of W is 20% or more, the wettability is good and carbide-
It is thought that the interfacial strength of the binder phase increased, 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.

fil Tungsten Carbide If the content of tungsten carbide is less than 15%, it is virtually impossible to stably dissolve 20 to 25% of W in the binder phase, and if it exceeds 50%, the wear resistance will deteriorate significantly; 15% or more due to the increase in the amount of skeleton and the deterioration of toughness.
It was set at 50%. Among them, 20 to 40% is most desirable.

(2) If the titanium carbide TiC is less than 10%, the desired wear resistance as a cermet cannot be obtained, and if it is more than 60%, the toughness of the alloy decreases because +'ltc itself is poor in toughness, so the content is 10 to 60%.
And so. Also, Ill i C is (Ti, W)CN
It is preferable to add it in the form of (TiMoW)CN (Ti r Ta, W)CN or the like.

(3) Tantalum carbide (TaC) has a fine-grained structure and contributes to improving the high-temperature properties of alloy 2, but if it is less than 5%, carbide particles will grow abnormally30
% or more, the toughness tends to deteriorate, so it was set at 5 to 30 inches.

(4) Molybdenum carbide Mo=C forms a peripheral structure around the carbide and contributes to improving the wettability with the binder phase, but the desired effect is not observed when it is less than 0.i, and when it is more than 20% So originally MOx
05 because C deteriorates the wear resistance of the alloy due to its low hardness.
~20%.

(5) Titanium nitride The addition of TiN improves the high temperature strength of the alloy.

Although an improvement in toughness has been observed, if it is less than 5%, the desired effect is not observed, and if it exceeds 30%, the wettability with the binder phase decreases, so it was set at 5 to 30%.

(6) Binding Phase If the binder phase is less than 5 inches, the toughness will be insufficient, and if it exceeds 20 inches, the strength at high temperatures will be weakened, and the desired properties will be obtained as a tough cermet with heat resistance, which is the object of the present invention. Since this is not possible, it was set at 5 to 20%. For cutting purposes, 8 to 15 inches is particularly desirable. (7) Amount of W in the binder phase If the amount of W in the binder phase is less than 20%, the desired carbide-bond phase wettability cannot be obtained. In addition, in order to increase the concentration to 25% or more, other means such as rapid cooling are required for manufacturing purposes, and C/
Unless the N ratio is set to 1 or less, it is difficult to obtain an alloy with a stable solid solution of 25% or more. In this case, defects such as bores may occur. Therefore, in terms of stable production, the W content should be 20~
It was set at 25%.

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

Example 1 First, (TiW)CN with a C/N atomic ratio of 1 or more, (Ti
Commercially available 'l'ic
(Average particle size 1.3 fi) Ti Co, s No,
s (ZOμ) TiN (1.2μ) We (1.0μ)
μ) Mo t C (1.5μ) and TaC (1.5μ)
．． After mixing an appropriate amount of powder (4μ) in a ball mill, reacting in vacuum at 1600 to 1900℃ for 2 hours for solid solution treatment, and after cooling, grinding with a ball mill to an average particle size of 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) CN+ (Ti 'ra W) C
N.

(TiMoW)CN and a binder phase powder are used, and the rest is the above-mentioned WC2TaC, etc., as needed.Then, the mixed powder is dried and then pressed to form a powder. The cermets 1 to 6 of the present invention were manufactured by molding the compacts and firing the green compacts in a vacuum of 10-3 to 10-'IilHg for 1 hour. The component compositions of the cermets 1 to 6 of the present invention are shown in Table 1. In addition, Table 1 (2 is a comparative cermet manufactured under the same conditions as the above-mentioned conditions for manufacturing the cermet of the present invention except that the alloy composition and binder phase composition were changed) A-B are also listed.

Next, regarding cermets B, C, D, and E for comparison with the above-mentioned inventive cermets 1.2.3.4 and 6, continuous and interrupted cutting and thermal crack comparison cutting tests were conducted under the cutting conditions shown below (without comparison) These results are also listed. has been done.

■Continuous cutting line V+<measurement of sag on cutting edge) Work material 8 CM440 (Hs 40) Depth of cut 2
．． 0111 Feed rate Q, 7 ml/rev Cutting speed 200 m/rrin Cutting time 30 seconds ■Intermittent cutting conditions Work material 8CM440 (Hs 40) Depth of cut 2.0 Tsuru Cutting speed 100 m/min Cutting time Each feed 1m1n ■Thermal crack Cutting conditions Work material 80M440 (Hs 40) Work material shape 5 x 300 x 200 Cutting speed 15
0 =/min Feed rate Q, 3111/blade depth of cut 21 Cutting time 1.5 m1n As is clear from Table 1, 1. The cermet of the present invention has extremely excellent heat crack resistance and plastic deformation resistance, and It can be seen that it is superior to inferior toughness, and no deterioration in toughness is observed.

Example 2 Same raw material powder and average particle size 1 as used in Example ■
．． 5μ Ni-Al (Ni: 70%, An: 30
%) alloy powder and the present invention cermet 7.8 and comparative cermet) F-H were manufactured under similar manufacturing conditions. Table 2 shows the physical properties of the binder phase component 9 alloy of both cermets and the same cutting test results as in Example 1. Second
As is clear from the table, the cermet of the present invention has plastic deformation resistance comparable to that of the γ' phase precipitated cermet, and is significantly superior in fracture resistance and heat crank resistance.

As mentioned above, the cermet of the present invention has excellent carbide-bond phase interface strength, is extremely resistant to thermal cracking, and has excellent toughness, so it is extremely effective in interrupted milling cutting where thermal cycles occur (something that conventional cermets were not good at). In addition to long life, it exhibits particularly stable performance in intermittent heavy cutting with large feed rates.

■It has excellent plastic deformation resistance and wear resistance due to significant solid solution strengthening of the binder phase, so it exhibits stable performance under high-speed, high-feed cutting conditions.

[Brief explanation of the drawing]

Figure 1 shows the WC of the alloy when the (/N ratio is taken as a parameter)
This figure shows the relationship between t and the amount of W solid solution in the binder phase. FIG. 2 shows the relationship between the amount of W solid solution in the binder phase and the rupture time in a high temperature creep test. Applicant Hitachi Cemented Carbide Co., Ltd. Figure 1 Alloy wc (**%) Figure 2 Sho-Apakuya/IW quantity procedure amendment 1 Indication of hand properties 1982 Patent Application No. 214796 3, person making the amendment Relationship with handmade work Patent applicant 4, date of amendment order February 8, 1980 (shipment date February 28, 1980)
5. Symmetry of correction

Claims (1)

[Claims] Tungsten carbide 15 at a weight ratio of 1 as a dispersed phase forming component
~50% titanium carbide 10-60%, tantalum carbide 5-3
01 Molybdenum carbide 0.5-20 t, titanium nitride 5-
In an alloy consisting of 5 to 20% of ferrous metals such as iron, conorct, nibkel, etc., the binder phase contains W in a weight ratio of 20 to 25%, in addition to unavoidable impurities.
A tough cermet characterized by % solid solution.