JP3368794B2 - Surface-coated cermet throw-away type cutting insert with a hard coating layer with excellent fracture resistance - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hardened surface layer formed on the surface of a substrate (hereinafter, referred to as a cermet substrate) composed of a titanium carbonitride-based cermet. The hardness at the cutting edge ridge portion where the flank and the rake face intersect (hereinafter, simply referred to as the cutting edge ridge portion) is made relatively higher than the hardness at the flank and the rake surface, whereby the surface of the base is formed. The hard coating layer to be subjected to physical vapor deposition (hereinafter, referred to as PVD) and / or chemical vapor deposition (hereinafter, referred to as CVD) is provided with excellent fracture resistance, so that fracture resistance is required. Surface-coated cermet throwaway type designed to provide long-lasting cutting performance without causing chipping or chipping (small chipping) on the cutting edge even when used for high-speed interrupted cutting. Cutting chip (hereinafter,
Simply referred to as a coated cutting tip). 2. Description of the Related Art Conventionally, generally, for example, JP-A-4-3415
No. 80, etc., containing 5 to 14% by weight of Co and / or Ni as a binder phase forming component;
Vickers hardness (hereinafter referred to as Hv), Hv: 140
For the internal hardness of 0 to 1800, the flank of the cutting edge,
A hard coating layer was formed on the surface of a cermet substrate having a surface hardened layer having a uniform hardness distribution with a maximum surface hardness of Hv: 2100 to 2500 on the cutting edge ridge portion and the rake face. 2. Description of the Related Art Coated cutting tips formed by vapor deposition using a PVD method and / or a CVD method with an average layer thickness of ２０20 μm are known, and it is also known that they are used for continuous cutting and interrupted cutting of, for example, steel. Have been.
Further, the cermet substrate constituting the above-mentioned conventional coated cutting tip is subjected to the following conditions: (a) a temperature rising rate to a sintering temperature: 1 to 3 ° C./sec; (b) a temperature from room temperature to 1100 to 1300 ° C. Heating atmosphere:
A vacuum of 0.1 torr or less, (c) a sintering temperature of 1100 to 1300 ° C.
Atmosphere for raising temperature to 0 to 1560 ° C: Nitrogen atmosphere of 5 to 100 torr, (d) Holding time and atmosphere at the above sintering temperature: 60 to
(E) Cooling: Furnace cooling in a vacuum atmosphere of 0.1 torr or less, under a condition satisfying the above conditions (a) to (e), a powder compact having a predetermined composition. It is also known to be manufactured by sintering a body. [0003] On the other hand, in recent years, the performance of cutting devices has been remarkably improved, and there is a strong demand for labor saving. Accordingly, the cutting process tends to be performed at a higher speed. In the case of a conventional coated cutting tip in which the hardness distribution of the surface hardened layer formed on the surface portion of the substrate does not change, if this is used, for example, when performing intermittent cutting of steel at a high speed, the hard coating layer may have insufficient fracture resistance. Due to the cause, chipping or chipping is likely to occur in the cutting blade, and the service life is currently reached in a relatively short time. [0004] Therefore, the present inventors have proposed:
From the viewpoint as described above, paying attention to the conventional coated cutting tip in which a surface hardened layer is formed on the surface of the cermet substrate,
As a result of a study aimed at improving the fracture resistance of the hard coating layer constituting the same, the content of Co and / or Ni as binder phase forming components was reduced to 17.5 to 27% by weight when the cermet substrate was sintered. When sintering is performed under the conditions (a) to (e), which are the above sintering conditions, the cooling atmosphere of the condition (e) is a nitrogen atmosphere of 1 to 5 torr, The cermet substrate after sintering has an Hv: 120
In contrast to the internal hardness of 0 to 1600, the cutting edge ridge line on the surface shows the highest surface hardness of Hv: 2200 to 2600 which is almost the same as the surface hardened layer of the conventional cermet substrate, but the flank surface And the rake face has a relatively lower H
v: a surface-hardened layer having the highest surface hardness of 1400 to 1800 is formed, and the surface of the cermet substrate on which such a surface-hardened layer is formed is hardened by PVD and / or CVD. When the coating layer is deposited, the resulting hard coating layer has excellent fracture resistance, and the effect of improving the fracture resistance of the hard coating layer is the same as that of the surface hardened layer formed on the cermet substrate surface. The hardness distribution, ie, the internal hardness indicating Hv: 1200 to 1600, the cutting edge ridge line shows the highest surface hardness of Hv: 2200 to 2600, while the flank and rake face are relatively more Low Hv: It is thought to be due to the fact that the hardness distribution showing the highest surface hardness of 1400 to 1800 significantly reduces the residual compressive stress of the hard coating layer, and thus The coated cutting insert resulting from the above requires chipping resistance, for example when used for high-speed interrupted cutting of steel, etc. The research results show that they can be used over a long period of time. The present invention has been made based on the results of the above research, and contains 17.5 to 27% by weight of Co and / or Ni as a binder phase forming component, and has an Hv: 1
For the internal hardness of 200 to 1600, the cutting edge ridge line shows the highest surface hardness of Hv: 2200 to 2600, and the flank and rake face show the highest surface hardness of Hv: 1400 to 1800. A hard coating layer having an average layer thickness of 1 to 20 μm is deposited on the surface of a cermet substrate having a hardened layer on the surface by a PVD method and / or a CVD method. The characteristic feature is the coated cutting tip having the following characteristics. [0006] The hardness distribution of the surface hardened layer formed on the surface of the cermet substrate constituting the coated cutting tip of the present invention is such that the content of Co and / or Ni as binder phase forming components is 17.5. After specifying the cooling atmosphere, the cooling atmosphere of the condition (e) of the conditions (a) to (e), which are the sintering conditions of the cermet substrate constituting the conventionally coated cutting tip, is set to 1 to 27% by weight as described above. It is adjusted by performing sintering under the condition of a nitrogen atmosphere of 5 torr, that is, the content of Co and / or Ni is reduced within the above range, and the pressure of the nitrogen atmosphere under the condition (e) is set within the above range. The higher the temperature, the higher the hardness of the ridge and the flank and rake face, and conversely, the higher the Co and / or Ni content within the above range, and the lower the pressure of the nitrogen atmosphere. When the content of the binder phase forming component exceeds 27% by weight and the nitrogen atmosphere is less than 1 torr, the maximum surface hardness of the cutting edge ridge portion is less than Hv: 2200. The maximum surface hardness of the flank and the rake face is less than Hv: 1,400. When such a hardness distribution is obtained, the difference in hardness from the internal hardness becomes too small, and the hard coating deposited on the The desired excellent fracture resistance of the layer cannot be ensured, while the content of the binder phase forming component is 17.5.
When the nitrogen atmosphere exceeds 5 torr with the content being less than 5% by weight, the maximum surface hardness of the cutting edge ridge portion exceeds Hv: 2600, and the maximum surface hardness of the flank and rake face is Hv:
It exceeds 1800, and as a result, the hardness difference from the internal hardness becomes too large. Even if such a hardness distribution is obtained, the hard coating layer does not have the desired effect of improving the fracture resistance. The hardness distribution of the hardened surface layer in the cermet substrate was determined as described above. Also, the average thickness of the hard coating layer was set to 1 to 20 μm,
If the thickness is less than 1 μm, the desired excellent abrasion resistance provided by the hard coating layer cannot be secured,
On the other hand, this is based on the reason that when the thickness exceeds 20 μm, a tendency to decrease the fracture resistance appears. Next, a coated cutting tip of the present invention will be described in detail with reference to examples. As raw material powder,
In any case, TiCN having a predetermined average particle size in the range of 0.5 to 2 μm [by weight (the same applies hereinafter), TiC / TiN
= 50/50] powder, TiN powder, TaC powder, NbC
Powder, WC powder, Mo ₂ C powder, VC powder, ZrC powder, Cr ₃ C ₂ powder, (Ti, W, Mo) CN [Ti /
W / Mo = 80/10/10, C / N = 70/30] powder, (Ti, Ta, V) CN [Ti / Ta / V = 70 /
20/10, C / N = 50/50] powder, (Ti, T
a, Nb) CN [Ti / Ta / Nb = 70/15/1
5, C / N = 60/40] powder, (Ti, W, Nb) C
N [Ti / W / Nb = 80/10/10, C / N = 70
/ 30] powder, (Ti, Nb, Mo) CN [Ti / Nb
/ Mo = 60/30/10, C / N = 60/40] powder, (Ti, W) CN [Ti / W = 80/20, C / N
= 70/30] powder, Co powder, and Ni powder were prepared, and these raw material powders were blended in the composition shown in Table 1, wet-mixed in a ball mill for 24 hours, dried, and dried.
A green compact is pressed at a pressure of ton / cm ² ,
Next, these green compacts were heated from the room temperature to 1300 ° C. in a vacuum atmosphere of 0.1 torr at a temperature rising rate of 1.5 ° C./min to increase the temperature to 1300 ° C.
After the temperature was raised to 150 ° C., the atmosphere was changed to a nitrogen atmosphere of 15 torr, the temperature was raised to 1500 ° C. at the same temperature rising rate, and the temperature was kept at 1500 ° C. for 60 minutes in the same atmosphere.
A cermet substrate A having a throw-away tip shape according to ISO standard SNMG120408 by sintering under a condition of furnace cooling in a predetermined nitrogen atmosphere within a range of torr and subjecting the sintered body to a round honing of 0.05 mm. M were each manufactured. Further, for the purpose of comparison, green compacts A to A having the same composition as shown in Table 1 were used, and the sintering thereof was performed in the final step of the above sintering conditions in which the furnace cooling was 0%. Cermet substrates a to m were produced under the same conditions except that the cermet substrates were carried out in a vacuum atmosphere of 0.1 torr. With respect to various cermet substrates obtained as a result, Hv (load: 300 g) of a flank and a rake face was measured at arbitrary 10 points, respectively, while the surface was polished, and the ridge of the cutting edge was accurately measured. Since the surface hardness cannot be measured, Hv (load: 300 g) at a position 0.05 mm inside from the honing surface in the polished cross section at 10 arbitrary points is measured and determined as the surface hardness, and the maximum surface hardness is selected from this. The results are shown in Tables 2 and 3 together with the internal hardness. Next, as shown in Tables 2 and 3, (a) the cermet substrate was ultrasonically cleaned in acetone and dried on an arc ion plating apparatus, as shown in Tables 2 and 3. Charged, while pure Ti and Ti-50% by weight were used as cathode electrodes (evaporation sources), respectively.
Al alloy, Ti-45 wt% Al-5 wt% Mg alloy,
And a Ti-40% Al-10% Cr alloy, and while the inside of the apparatus is evacuated and kept at a vacuum of 1 × 10 ⁻⁵ torr, the inside of the apparatus is heated to 500 ° C. with a heater, and then argon gas is introduced. Then, an argon gas atmosphere of 1 × 10 ⁻³ torr was applied, and in this state, a bias voltage of −800 V was applied to the cermet substrate to bombard the surface of the cermet substrate, and then, in the apparatus, depending on the composition of the hard coating layer, ,
Nitrogen gas, methane gas, or a mixture of nitrogen gas and methane gas was introduced as a reaction gas to form a reaction atmosphere of 5 × 10 ⁻³ torr, and the bias voltage applied to the cermet substrate was reduced to −200 V. An arc discharge is generated between the electrode and the electrode to form a hard coating layer having a composition and an average layer thickness shown in Tables 5 and 6 on each surface of the cermet substrate.
Method D, (b) CVD method of forming a hard coating layer having a composition and an average layer thickness shown in Tables 5 and 6 under the conditions shown in Table 4 using a normal CVD apparatus. By forming the hard coating layer by the method (b), the coated cutting tips 1 to 13 of the present invention and the comparative coated cutting tips 1 to 1 are formed.
3 were each manufactured. [0010] With respect to the various coated cutting tips obtained as a result, a work material: JIS SCM440C, a round bar with four longitudinal grooves at regular intervals in the longitudinal direction, a cutting speed: 350 m / min, a feed: 0.2 mm / rev A high-speed intermittent cutting test of the alloy steel was performed under the following conditions: cutting depth: 1 mm, cutting time: 5 minutes, and the flank wear width of the cutting edge was measured. Tables 5 and 6 show the results of these measurements. [Table 1] [Table 2] [Table 3] [Table 4] [Table 5] [Table 6] From the results shown in Tables 5 and 6, all of the coated cutting tips 1 to 13 of the present invention have relatively high hardness in the hardened surface layer of the cermet substrate constituting the same. Due to the ridges and the relatively low hardness flank and rake surfaces, the hard coating layer has excellent chipping resistance, resulting in chipping and chipping of the cutting edge even in high-speed interrupted cutting of steel. In contrast, the comparative coated cutting tips 1 to 13, which show excellent cutting performance but have no change in hardness in the surface-hardened layer of the cermet substrate, similarly to the above-mentioned conventional coated cutting tips, all have hard coating layers. It is evident that chipping and chipping easily occur in high-speed intermittent cutting of steel, which results in cutting under severe conditions, resulting in a short service life in a relatively short time. As described above, the coated cutting tip of the present invention has a maximum surface hardness of Hv: 2200 to 2600 of the cutting edge ridge portion in the surface hardened layer of the cermet substrate constituting the chip, and an Hv of the flank and rake face: 1400-1
The hardness distribution of the highest surface hardness of 800 makes the hard coating layer formed on it have excellent fracture resistance, so it can be cut not only in high-speed continuous cutting of steel but also in high-speed interrupted cutting. Without chipping or chipping of the blade,
It exhibits excellent cutting performance over a long period of time.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hisashi Tsujizaki 1511 Furamagi, Ishishita-cho, Yuki-gun, Ibaraki Pref. Address Mitsubishi Materials Corporation Tsukuba Works (56) References JP-A-2-88742 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23B 27/14 C23C 14/00-14 / 58 C23C 16/00-16/56

Claims (1)

(57) [Claim 1] Coin and / or Ni are contained as a binder phase forming component in an amount of 17.5 to 27% by weight, and each of them has an internal hardness of 1200 to 1600 in Vickers hardness. On the other hand, the surface hardening in which the ridge of the cutting edge where the flank and the rake face of the cutting edge intersect has a maximum surface hardness of 2200 to 2600, and the flank and rake face have a maximum surface hardness of 1400 to 1800. A hard coating layer obtained by physical vapor deposition and / or chemical vapor deposition of a hard coating layer having an average layer thickness of 1 to 20 μm on the surface of a substrate composed of a titanium carbonitride-based cermet having a layer on its surface is excellent. Surface-coated cermet throw-away type cutting tip with excellent fracture resistance.