JP2000052105A - Surface coated silicon nitride ceramics throwaway type cutting tip excellent in chipping resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface coated Si3N4 ceramics throwaway type cutting tip excellent in chipping resistance. SOLUTION: A ceramics substrate is formed of Si3N4 ceramics having a Si3N4 phase: 85-95%, a (Zr, R) O2 phase: 0.5-5%, and a ZrN phase: 0.1-5%, if required, all of which form dispersed phases, and having a remaining impurity composition with a combined phase formed of R-Mg-Si-Zr-O-N phase (R is rare earth metal). A soft layer having an organization with the rate of the Si3N4 phase to the (Zr, R)O2 phase being 20-60% is formed ranging from the surface of the substrate to its depth of 1-5 μm. Further, a hard coating layer is formed of one or two type of a Ti compound layer consisting of a TiC layer, a TiN layer, a TiCN layer, a TiCO layer, a TiNO layer and a TiCNO layer and a hard coating layer consisting of Al2O3 layer, with its average layer thickness being 1-10 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has excellent chipping resistance, and is particularly effective in preventing chipping (small chipping) of a cutting edge when performing intermittent cutting of cast iron under heavy cutting conditions such as high feed and high cutting. The present invention relates to a throw-away type cutting tip (hereinafter, referred to as a coated cutting tip) made of surface-coated silicon nitride ceramics which exhibits excellent cutting performance for a long time without generation.

[0002]

2. Description of the Related Art Conventionally, a large number of coated cutting tips have been proposed in which a hard coating layer is chemically vapor-deposited on the surface of a silicon nitride-based ceramic substrate (hereinafter, referred to as a ceramic substrate). It is well known that it is used for cutting.

[0003]

On the other hand, in recent years, there has been a strong demand for labor saving and energy saving of cutting work, and with this, cutting work has been speeding up and heavy cutting such as high feed and high cutting has been performed. However, in the case of conventional coated cutting inserts, chipping tends to occur in the cutting edge, especially when it is used in heavy cutting conditions for interrupted cutting of cast iron, which leads to a relatively short service life. Is the current situation.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
From the above-mentioned viewpoints, as a result of researching to develop a coated cutting tip having excellent chipping resistance, (a) silicon nitride (hereinafter, referred to as Si ₃ N ₄ ) using a ceramic substrate as a raw material powder Powder, rare earth element oxide (hereinafter referred to as R ₂ O ₃ ) powder, silicon oxide (hereinafter referred to as S
iO ₂ ) powder, magnesium oxide (hereinafter referred to as MgO)
) And zirconium nitride (hereinafter ZrN).
The raw material powders are mixed into a prescribed composition using powders, wet-mixed with ethyl alcohol in a ball mill, a molding binder is added, and the mixture is dried by spray drying to obtain granules. It is press-formed into a green compact having a predetermined cutting tip shape by a press, and this green compact is first subjected to a pressure of 0.2 to 10 MPa (2 to 100 kg).
f / cm ² ) in a pressurized nitrogen atmosphere, 1700 to 1900
Primary sintering under the condition of maintaining the temperature at a predetermined temperature for a predetermined time, and then increasing the pressure to a pressure of 50 to 200 MPa (500 to 200
0 kgf / cm ² ), and the temperature is approximately
It is manufactured by holding at a temperature of 1900 ° C. for a predetermined time and then performing secondary sintering under cooling conditions, and by microscopic observation with a scanning electron microscope, a Si ₃ N ₄ phase: 85 to 95%, a rare earth element containing Y ( (Hereinafter, represented by R) is a stabilized zirconia [hereinafter, represented by (Zr, R) O ₂ ] phase formed by solid solution in zirconia (hereinafter, represented by ZrO ₂ ): 0.
5 to 5%, and if necessary, a ZrN phase: 0.1 to 5%, each of which constitutes a dispersed phase, and the remainder is a composite oxynitride of the rare earth element, Mg, Si, and Zr. It has a composition consisting of a binder phase composed of a solid solution (hereinafter, referred to as R-Mg-Si-Zr-ON) phase and unavoidable impurities (all area%, and the following% each indicate area%). S
Specific to i ₃ N ₄ ceramics. (B) In producing the ceramic substrate of (a),
In the cooling process of the secondary sintering, the temperature is 1500 to 1600.
When the temperature was lowered to 30 ° C., the temperature was maintained at this temperature for 30 minutes to 2 hours. The surface of the surface was observed at an arbitrary depth by scanning electron microscopy to observe the structure of the Si ₃ N ₄ phase and (Zr, R).
It consists O ₂ phase, and the (Zr, R) ratio of O ₂ phase can form a relatively high surface layers than the inner substrate, the surface layer, the (Zr, R) O Extremely soft because the content of _two phases is extremely high. (C) In general, the occurrence of chipping of the cutting blade can be suppressed by forming a soft layer on the flank of the cutting blade, while the soft layer on the rake surface of the cutting blade causes local wear of the rake surface. Therefore, when the surface layer (soft layer) of the rake face of the cutting edge is polished and removed so that the soft layer exists only on the flank face of the cutting edge of the ceramic base, intermittent cutting of cast iron is particularly performed under heavy cutting conditions. To exhibit excellent chipping resistance. (D) For the soft layers on the rake face and the flank face of the cutting edge of the ceramic base formed in the above (a) to (c), a carbide (TiC) layer of Ti, a nitride ( Hereinafter, a TiN layer and a carbonitride (hereinafter referred to as T
iCN) layer, carbonate (hereinafter referred to as TiCO)
A hard coating layer composed of a Ti compound layer consisting of a layer, a nitrided oxide (hereinafter referred to as TiNO) layer, and a carbonitrided oxide (hereinafter referred to as TiCNO) layer exhibits high adhesion. The research results shown in (a) to (d) above were obtained.

The present invention has been made based on the above research results.
And a hard coating on the surface of the ceramic substrate.
In the coated cutting tip formed by chemical vapor deposition of the covering layer,
Structure observation of the ceramic substrate with a scanning electron microscope
And Si_ThreeN_FourPhase: 85-95%, (Zr, R) O
_TwoPhase: 0.5-5%, ZrN phase as required: 0.1-
5%, each of which constitutes a dispersed phase
And the rest is composed of the R-Mg-Si-Zr-ON phase.
Having composition consisting of bonded phase and unavoidable impurities_ThreeN
_FourThe cutting edge of the base
On the beveled part, also by microscopic observation with a scanning electron microscope,
Substantially over the depth of 1 to 5 μm from the surface of the substrate,
Si_ThreeN_FourPhase and (Zr, R) O_TwoConsisting of phases and
In the measurement of the flank surface of the cutting edge, the (Zr, R) O _Two
Forming a soft layer in which the proportion of the phase occupies 20 to 60 area%,
Further, the hard coating layer is made of a TiC layer, a TiN layer, a TiC layer.
N layer, TiCO layer, TiNO layer and TiCNO layer
One or more of the Ti compound layers
l_TwoO_ThreeConsisting of a hard coating layer consisting of
Immediate chipping resistance with a layer thickness of 1 to 10 µm
The characteristic feature is that the coated cutting tip is featured.

[0006] Next, in the coated cutting tip of the present invention, the composition of the ceramic base, the ratio and formation depth of the (Zr, R) O ₂ phase of the soft layer, and the average layer thickness of the hard coating layer are described. The reason for limiting as described above will be described. (A) Proportion of Si ₃ N ₄ Phase of Ceramic Substrate Since the Si ₃ N ₄ phase has a β-type crystal structure and exists as hard needle-like crystals, the strength is secured by the needle-like crystals, and the resistance is high. It contributes to the improvement of abrasion, but the ratio is 85
If it is less than 95%, the proportion of the binder phase becomes relatively too large to secure the desired wear resistance. On the other hand, if the proportion exceeds 95%, on the contrary, the binder phase becomes too small, and as a result, Since the sinterability is remarkably reduced, the strength is reduced and the cutting edge is apt to be chipped, the ratio is 85 to 9
It was determined to be 5%.

(B) (Zr, R) O of ceramic substrate
Ratio of _two phases The ratio of (Zr, R) O ₂ phase is determined by
R) The ratio of the O ₂ phase is determined to be 20 to 50%, and if the ratio is less than 0.5%, the (Z) of the soft layer
When the proportion of the (r, R) O ₂ phase is less than 20%, a sufficient softening effect to exhibit the desired excellent chipping resistance cannot be obtained. On the other hand, when the proportion exceeds 5%, Si
Not only so high strength is impaired provided by ₃ N ₄ phase, the soft layer (Zr, R) ratio of O ₂ phases also becomes higher than 60% plastic deformation in the soft layer The ratio is determined to be 0.5 to 5%, since it tends to occur and causes uneven wear.

(C) Proportion of ZrN phase in ceramic substrate Since the ZrN phase has an effect of improving abrasion resistance, it may be present if necessary. If the proportion is less than 0.1%, a desired abrasion resistance is obtained. No improvement effect is obtained, while the ratio is 5
%, The toughness is reduced, and chipping or chipping occurs on the cutting edge.
%.

(D) The soft layer at the flank of the cutting edge (Zr,
R) O ₂ phase ratio As described above, the (Zr, R) O ₂ phase forms a soft layer on the flank of the cutting edge of the ceramic base when coexisting with the Si ₃ N ₄ phase. Although there is an effect of suppressing the occurrence of chipping on the cutting edge even under heavy cutting conditions, the ratio is less than 20% in the measurement of the surface of the flank of the cutting edge. If the ratio is less than 20%, the desired effect cannot be obtained. Is also 6
If it exceeds 0%, the abrasion resistance rapidly decreases, so the ratio is set to 20 to 60%.

(E) Depth of the soft layer If the depth is less than 1 μm, the effect of improving the chipping resistance by the soft layer cannot be sufficiently exhibited. It is easy to occur and causes uneven wear.
It was decided.

(F) Average Layer Thickness of Hard Coating Layer If the layer thickness is 1 μm, the desired excellent wear resistance cannot be ensured. On the other hand, if the layer thickness exceeds 10 μm,
Since chipping and chipping easily occur in the cutting blade, the layer thickness is set to 1 to 10 μm.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The coated cutting tip of the present invention will be specifically described with reference to examples. As a raw material powder, any of Si having a predetermined average particle size in the range of 0.1 to 1 μm.
₃ N ₄ powder, various R ₂ O ₃ powders shown in Table 1, Si
O ₂ powder, MgO powder, and ZrN powder were prepared, and these raw material powders were blended in the composition shown in Table 1, and wet-mixed for 48 hours in a ball mill using ethyl alcohol as a solvent. Glycol was added and dried by spray drying to obtain granules, which were then pressed with a uniaxial press at a pressure of 1 ton / cm ² into a granule.
The green compacts A to J having the cutting tip shape of IS • SNMN120408 are formed, and each of the green compacts A to J is first subjected to 0.2 to 10 MPa (2 to 100 kgf / cm).
² ) in a pressurized nitrogen atmosphere at a predetermined pressure within the range of 170)
Primary sintering is performed at a predetermined temperature in a range of 0 to 1900 ° C. for a predetermined time in a range of 1 to 4 hours, and then the pressure is increased to 50 to 200 MPa (500 to 2000 kgf /
cm ² ), and the temperature is maintained at the same predetermined temperature in the range of 1750 to 1900 ° C.,
After maintaining the temperature at this temperature for a predetermined time within the range of 0.5 to 2 hours, cooling is started.
When the temperature drops to a predetermined temperature in the range of ~ 1600 ° C,
Secondary sintering is performed at this temperature for a predetermined time within a range of 30 minutes to 2 hours. Honing polishing is performed on the cutting edge ridge line where the rake face and flank of the sintered body after the secondary sintering intersect. Then, the upper and lower surfaces (rake face) were also polished, and removed over a depth of 10 μm from the surface, thereby producing ceramic substrates A to J of the present invention, respectively. Also,
For the purpose of comparison, a comparative ceramic substrate having no soft layer formed on the flank of the cutting edge under the same conditions as the production conditions of the ceramic substrates A to J of the present invention except that the cooling after the secondary sintering is furnace cooling. a to j were respectively manufactured.

With respect to the various ceramic substrates obtained as a result, the surface of the flank surface of the cutting blade, the surface of the rake surface of the cutting blade, and the internal cross section are observed using an X-ray microanalyzer and a scanning electron microscope. The depth of the soft layer was measured by observing the cross section of the flank of the blade. Tables 2 and 3 show the measurement results. Since the surface and the internal cross section of the rake face of the cutting edge showed almost the same composition and structure, Tables 2 and 3 show the measurement results of the surface of the rake face of the cutting edge.

Next, the surface of each of these various ceramic substrates was coated using a conventional chemical vapor deposition apparatus, as shown in Table 4 (* in the table).
The marks have a vertically-grown crystal structure described in JP-A-6-8010) under the conditions shown in Table 5,
The coated cutting tips 1 to 10 of the present invention and the comparative coated cutting tips 1 to 10 were produced by forming a hard coating layer composed of a Ti compound layer and an Al ₂ O ₃ layer having the composition and target layer thickness shown in FIG. .

Next, the coated cutting inserts 1 to 5 of the present invention described above.
Using 10 and comparative coated cutting tips 1 to 10, Work material: round bar with four longitudinal grooves at equal intervals in the longitudinal direction of FC300, cutting speed: 600 m / min, feed: 0.8 mm / rev, cutting depth: 2 mm , Cutting time: 10 minutes, Dry high-feed intermittent cutting test of cast iron under the following conditions; Work material: Round bar with four longitudinal grooves at regular intervals in the longitudinal direction of FC250, Cutting speed: 500 m / min, Feed: 0.3 mm / rev, depth of cut: 5 mm, cutting time: 10 min.
In each cutting test, the flank wear width of the cutting edge was measured.
Table 7 shows the results of these measurements.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

[Table 3]

[0019]

[Table 4]

[0020]

[Table 5]

[0021]

[Table 6]

[0022]

[Table 7]

[0023]

According to the results shown in Tables 1 to 7, all of the coated cutting tips 1 to 10 of the present invention perform intermittent cutting of cast iron under heavy cutting conditions by using a soft layer existing on the flank of the cutting edge of the ceramic substrate. Nevertheless, the comparative coated cutting tips 1 to 10 in which the cutting edge does not generate chipping and exhibit excellent wear resistance, whereas the softened layer is not formed on the flank of the cutting edge of the ceramic base. It is clear that in each case, chipping occurs on the cutting blade, which causes a short service life in a relatively short time. As described above, the coated cutting tip of the present invention has excellent chipping resistance, and can be used not only for continuous cutting and intermittent cutting under ordinary conditions, but also for intermittent cutting particularly under heavy cutting conditions for cast iron. It exhibits excellent cutting performance over a long period of time without causing chipping or the like, and can sufficiently satisfy labor-saving and energy-saving cutting operations.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C23C 16/30 C04B 35/58 102K F-term (Reference) 3C046 FF04 FF22 FF25 FF33 FF40 FF42 FF47 FF49 FF51 FF55 4G001 BA04 BA06 BA08 BA09 BA10 BA32 BA39 BA75 BA82 BB03 BB08 BB09 BB10 BB14 BB25 BB32 BB38 BB51 BB53 BB57 BB67 BC13 BC57 BC72 BC73 BD12 BD18 BE11 4K030 AA02 AA10 AA14 AA17 AA18 AA24 BA18 BA05 BA41

Claims (2)

[Claims] 1. A surface-coated silicon nitride ceramic indexable cutting tip formed by chemical vapor deposition of a hard coating layer on the surface of a silicon nitride ceramic substrate, wherein the substrate is obtained by microscopic observation with a scanning electron microscope. Silicon nitride phase: 85 to 95 area%; stabilized zirconia phase in which at least one of the rare earth elements including Y forms a solid solution in zirconia: 0.5 to 5 area%. Are all composed of a dispersed phase, the rest being composed of a silicon nitride-based ceramic having a composition consisting of a binder phase composed of the above-mentioned rare earth element, a composite oxynitride solid solution phase of Mg, Si and Zr, and an unavoidable impurity. On the flank of the cutting edge of the substrate, the above-mentioned silicon nitride phase and the above-mentioned stabilizing die were substantially observed over a depth of 1 to 5 μm from the surface of the substrate by microscopic observation with a scanning electron microscope. In the measurement of the surface of the cutting edge flank, a soft layer comprising a zirconia phase and having a ratio of the stabilized zirconia phase of 20 to 60% by area is formed. Material layer,
One or more of Ti compound layers consisting of a carbonitride layer, a carbon oxide layer, a nitrogen oxide layer, and a carbonitride layer, and an aluminum oxide layer, and the average layer thickness is 1 A throw-away type cutting tip made of surface-coated silicon nitride-based ceramics having excellent chipping resistance, characterized by having a thickness of from 10 to 10 μm. 2. A cutting insert made of surface-coated silicon nitride-based ceramics obtained by chemical vapor deposition of a hard coating layer on the surface of a silicon nitride-based ceramics substrate, wherein the substrate is obtained by microscopic observation with a scanning electron microscope. Silicon nitride phase: 85 to 95 area%; stabilized zirconia phase in which at least one of the rare earth elements including Y is solid-dissolved in zirconia: 0.5 to 5 area%; zirconium nitride phase: 0.5 to 5 area%. 1 to 5 area%, each of which constitutes a dispersed phase, with the balance being composed of a binder phase composed of the above-mentioned rare earth element, a composite oxynitride solid solution phase of Mg, Si and Zr, and unavoidable impurities. In addition to being composed of a silicon nitride-based ceramic having a composition, on the flank of the cutting edge of the base, the structure is also observed with a scanning electron microscope over a depth of 1 to 5 μm from the surface of the base. Forming a soft layer substantially consisting of the silicon nitride phase and the stabilized zirconia phase, wherein the ratio of the stabilized zirconia phase occupies 20 to 60 area% in the measurement of the cutting edge flank surface; The hard coating layer, Ti carbide layer, nitride layer,
One or more of Ti compound layers consisting of a carbonitride layer, a carbon oxide layer, a nitrogen oxide layer, and a carbonitride layer, and an aluminum oxide layer, and the average layer thickness is 1 A throw-away type cutting tip made of surface-coated silicon nitride-based ceramics having excellent chipping resistance, characterized by having a thickness of from 10 to 10 μm.