JPS63130743A - Nitrogen-containing cermet - Google Patents

Abstract

PURPOSE:To enhance resistance to thermal cracking and chipping and to improve a machining characteristic by specifying the content of Ti in the metal atoms of a hard dispersion phase, the content of N in the nonmetal atoms therein and the occupying ratio of a bond metal phase and incorporating a specific ratio of CBN therein. CONSTITUTION:The content of Ti in the metal atoms of the hard dispersion phase of nitrogen-contg. cermet consisting of double carbonitride of Ti, Ta, W, and Mo as the hard dispersion phase and the metal consisting of Ni and Co as the bond metal phase is specified to 0.5-0.95 atomic ratio. The content of N in the nonmetal atom is specified to 0.1-0.9 and the ratio at which said bond metal phase occupies in the alloy is specified to 3-50wt%. In addition, the CBN powder is incorporated at 0.1-10wt% therein. The above-mentioned CBN powder is dispersed into the alloy of such cermet, by which the quantity of the heat generated at a blade edge at the time of cutting is quickly dissipated to suppress thermal expansion and to decrease the generation of thermal cracks. The nitrogen-contg. cermet which is improved in the resistance to chipping and has the extremely high machining characteristic is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is an extremely strong and highly durable cutting tool useful in the field of cutting tools that can be used, for example, under harsh conditions such as high speed, high feed cutting and severe interrupted cutting. It concerns quality nitrogen-containing cermets.

(Prior art) A nitrogen-containing cermet in which double carbonitrides of Ti, Ta, W, and Mo are bonded with a metal consisting of Ni and CO has a hard dispersed phase that is significantly finer than a conventional cermet that does not contain nitrogen. As a result, high temperature creep resistance is significantly improved.

However, cermets containing Ti(CN) as a main component have a drawback of being inferior in heat cracking resistance during interrupted cutting such as milling, compared to so-called cemented carbide containing WC as a main component. This means that the thermal conductivity of cemented carbide is approximately 1.
．． 0 W/cm·K, whereas that of cermet is approximately 0.17 W/cm-K. This is because the heat dissipation does not follow the heat generation and the heat is concentrated at the cutting edge.

As a countermeasure to this problem, an attempt has been made to increase the proportion of nitrogen in double carbonitride, which is a hard dispersed phase, and to increase the content of TiN in order to improve fracture toughness and thermal shock resistance (Japanese Patent Publication No. 54-28129). ).

It has also been proposed to add AIN or Al4C3 to eliminate residual bores (for example, JP-A-58-12
No. 6954).

(Problems to be Solved by the Invention) However, these conventional techniques have not yet completely eliminated structural defects such as bores, and do not have sufficient strength for interrupted cutting. Even in continuous cutting,
As the work material becomes more difficult to cut, the diffusion of heat that depends on thermal conductivity cannot keep up with the amount of heat generated, and the material becomes inferior in plastic deformation resistance.

Further, alloys containing a large amount of nitrogen have a problem of insufficient wear resistance.

The inventors conducted studies in view of the problems of the conventional method described above, and as a result, they arrived at the present invention.

(Means for solving problems) That is, the nitrogen-containing cermet of the present invention contains Ti and Ta.

Double carbonitrides of W and Mo are used as the hard dispersed phase, and Ni (!
: In a nitrogen-containing cermet having a metal composed of Co as a bonding metal phase, the amount of Ti in the metal atoms of the hard dispersed phase is 0.5 or more and 095 or less in atomic ratio, and the amount of Ti in the nonmetal atoms is
The bonding metal phase occupies 3 to 50% by weight in the alloy, and contains 01 to 10% by weight of CBN powder. .

In other words, CBN (13W/cm-K) has extremely high thermal conductivity and minimizes the content of nitrogen, which tends to cause bore formation.
powder. Furthermore, CBN is completely thermally stable up to 1 soo'c under normal pressure under vacuum and nitrogen or argon atmospheres, which are the usual sintering conditions for cermets, and does not transform into hBN, which is a high-temperature phase. It is also very preferable.

(Function) A problem with cermet as a tool is the occurrence of so-called thermal cracks vertically from the surface to the inside during interrupted cutting. There are various disagreements as to why cermets are more prone to thermal cracking than cemented carbide, but
One of the causes is considered to be dimensional changes caused by thermal expansion due to the rapid temperature rise of the cutting edge immediately after the start of cutting and contraction during idle running. Therefore, in addition to the coefficient of thermal expansion, the key point is how quickly the large amount of heat generated at the cutting edge can be dissipated.

Therefore, using the means shown above, CB with high thermal conductivity
By dispersing N into the alloy, the amount of heat generated at the cutting edge during cutting can be quickly dissipated throughout the alloy, suppressing thermal expansion and reducing the occurrence of thermal cracks.

Below, various reasons for limitations in the present invention will be explained.

(1) The composition of the double carbonitride of the components i, Ta, Mo, and W of the hard dispersed phase indicates that when the proportion of Ti in the metal atoms is less than 0.5 in atomic ratio, the wear resistance of the cermet is insufficient. However, if it exceeds 0.95, the sinterability deteriorates, which is not preferable. Further, if the proportion of nitrogen in the nonmetallic atoms is less than 0.1 in terms of atomic ratio, there is no effect of suppressing the grain growth of the hard dispersed phase during sintering, and if it exceeds 0.9, the sinterability will be poor, which is not preferable.

(2) Amount of binder metal phase in the alloy If it is less than 6% by weight, toughness will be insufficient, and if it exceeds 50% by weight, wear resistance will be insufficient, which is undesirable. (3) Amount of CBN powder in the alloy will be 0. If it is less than 1% by weight, there is no heat dissipation effect;
If it exceeds % by weight, the sinterability will be poor and undesirable.

In the present invention, it goes without saying that the effect remains the same even if the metal elements in the double carbonitride in the hard dispersed phase are replaced with V, Cr, Zn, Nb, Hf, etc. or added.

(Example) Examples of the present invention will be described below.

Example 1 Commercially available Ti(CN), TaC, WC, Mo2C, CBN
, C, Ni, and Co powders were counted, mixed, and press-molded, then heated in a vacuum sintering furnace at 1000° C. and sintered at 1480° C. for 1 hour at a nitrogen partial pressure of 20 Torr. The composition of the obtained cermet is expressed in molar ratio (Tio, 85Ta
o. 5Wo, 06Moo,. 4) (CO, 58NO,
42) 0.9-7” 1wt%Co-7,8wt%Ni
-2.5% by weight CBN. This cermet is referred to as A, and the one obtained by subjecting cermet A to hot isostatic pressing treatment (hereinafter referred to as HIP treatment) at 1400°C, 1000 atm for 1 hour is referred to as cermet B0.In addition, T1CN, TaC, WC, Mo2C ,C,Ni
+Co powder at 1450℃ elemental partial pressure sT'or
The cermet sintered at r for 1 hour is designated as C. The composition of this cermet C is (T10.87'Iho, (6W
o, @s Mo 0.02 )(C(1,55N 6.
45) g, g 7-0wt%Co-7,4wt%N
It was i.

Furthermore, the composition created by the same method as the above cermet Δ is (TiO, 82TaO, 04WO, 08M00.06)
(C0,55NO045)0.9-7.1wt%C0-
The cermet which is 7.5% by weight Ni-12.1% by weight CBN is designated as D. However, the cermet DJfi did not shrink sufficiently and many bores remained.

The thermal conductivities of these four types of cermets A, B, C, and D are A: 0.78 W/σ·K and B: 0.78 W/σ·K.
81 W/cm-K.

C: 0.18W/1m'K, D: 0.82
It was W/cm・K.

The transverse rupture strength and hardness of these cermets are shown in Table 1.

Thermets containing an appropriate amount of CBN) A has improved alloy properties compared to C and D, and BFi has been further subjected to HIP treatment.
It showed even better characteristics.

Table 1 Next, the cutting performance of these cermets A to D was tested under the following conditions.

Cutting conditions 1゜Work material: SCM435 (HB=240), 100mX
Square timber of IDO++IIn.

Cutting speed: 150 m/min, feed: 0, 2
5mm/rev.

Depth of cut: 2.5 wn, tip shape: 5PG4
22.

Cutter: DPG4160R, cutting time = 10 minutes As a result, no thermal cracks occurred in cermets A and BK/-J, and the flank wear amount was 0.28 for A and 0.28 for wn1B.
It was 21 years old.

On the other hand, in Cermet C, six thermal cracks occurred, and chipping occurred from five of them. Further, the flank wear amount was 0.35wn.

Cermet D broke off immediately after the start of cutting.

Example 2 Various alloys shown in Table 2 were prepared from various powders in the same manner as in Example 1, and these were heated at 1450'C under a nitrogen partial pressure of 3° Torr.
It was sintered for 1 hour. Table 3 shows the amount of flank wear and the number of thermal cracks generated under cutting conditions 2 shown below.

Cutting conditions 2 Work material: 545C (HB=270), 5D+mnX1
00wn angle.

Cutting speed: 170m/min, feed: 0.05mm/r
ev.

Mini cut 0.2 m, f knob shape: SD
KN42MT.

Cutter: FPG4100R, Cutting time: 20 minutes Table 3 (Effects of the invention) As detailed above, according to the present invention, thermal cracks at the cutting edge are prevented by incorporating CBN with high thermal conductivity into the nitrogen-containing cermet. It suppresses the occurrence of cracks and has good heat cracking resistance.
Still, it has the excellent effect of providing a nitrogen-containing cermet with improved chipping resistance and extremely high cutting properties.

Claims (1)

[Claims] (1) In a nitrogen-containing cermet in which a hard dispersed phase is a double carbonitride of Ti, Ta, W, and Mo, and a bonded metal phase is a metal consisting of Ni and Co, the amount of Ti in the metal atoms of the hard dispersed phase is The atomic ratio is 0.5 or more and 0.95 or less, the amount of N in the nonmetallic atoms is 0.1 or more and 0.9 or less in atomic ratio, and the bonded metal phase accounts for 3 to 50% by weight in the alloy. A nitrogen-containing cermet characterized by containing 0.1 to 10% by weight of CBN powder.