JPH068507B2 - Method for producing coated cemented carbide tool - Google Patents

Description

TECHNICAL FIELD The present invention relates to a coated cemented carbide tool with a further improved tool life.

[Problems to be Solved by Prior Art and Invention]

Generally, one or more of carbides, nitrides and carbonitrides of metals of groups 4a, 5a and 6a of the Periodic Table of the Elements and one or more of Co, Ni and Fe are selected. A cemented carbide tool having a composition containing is known, and further, on the surface of the cemented carbide tool, the above-mentioned 4a, 5a
And a single layer of one of the following: Group 6a metal carbides, carbonitrides, nitrides, oxides, oxycarbides, oxynitrides, and oxycarbonitrides, and aluminum oxides.
A coated cemented carbide tool has also been proposed, which is intended to extend the life of the tool by coating a multi-layer hard layer composed of at least one kind.

However, in the cemented carbide tool, since the hard layer is more brittle than the cemented carbide substrate, the toughness of the substrate itself is offset by the hard layer,
As a result, the toughness of the surface portion of the tool becomes low, so that the desired tool life cannot be extended.

In addition, a coated cemented carbide tool with a cemented carbide substrate of low hardness and toughness has been proposed from the above, but in this case, the heat plastic deformation and wear resistance are deteriorated. Therefore, it is difficult to extend the tool life. On the other hand, on the other hand, the toughness was further reduced in the coated cemented carbide tool, which adopted a cemented carbide substrate with high hardness to improve the heat plastic deformation and wear resistance and prolong the life of the tool. As a result, the toughness of the cutting tool often results in a loss of the tool at an early stage, leading to the end of the tool life. For this reason, the usage of the cutting tool is considerably limited under the present circumstances.

[Means for solving problems]

The present invention provides a coated cemented carbide tool that solves the problems of the coated cemented carbide tools described above, and includes carbides, nitrides, and carbides of metals of groups 4a, 5a and 6a of the Periodic Table of Elements. One or more carbonitrides, and C
On the surface of a cemented carbide substrate containing one or more of o, Ni, and Fe, a layer having a toughness and a softness higher than that of the cemented carbide substrate is provided. In a coated cemented carbide having an intermediate layer having a hardness gradient in which the hardness continuously increases toward the hard alloy substrate side, the coating layer has carbides, nitrides of group 4a, 5a, and 6a metals, Carbonitride, oxide, oxycarbide, oxynitride,
And oxycarbonitride, and a chemical vapor deposition method comprising a single layer consisting of one or more of aluminum oxide and two or more kinds, and the vapor deposition method is a coating treatment at 700 ° C. to 900 ° C. and 950 ° C. to 1050 ° C. A coated cemented carbide tool characterized in that a coating layer of a single layer or multiple layers is coated by both or the former of the chemical vapor deposition method of coating treatment. By forming a coating layer of a chemical vapor deposition method for performing a coating treatment at 700 ° C. to 900 ° C. on the above cemented carbide substrate, it is possible to prevent a decrease in strength mainly due to a decarburized layer at the time of coating accompanying the formation of the intermediate layer. , The intermediate layer is tougher and softer than the cemented carbide substrate, and has a hardness gradient in which the hardness continuously increases from the intermediate layer side to the cemented carbide substrate side,
In the cemented carbide base material after the coating, all have Vickers hardness, the surface hardness of the cemented carbide base material is 900 to 1100 kg / m ² , and the hardness at a depth of 15 μm from the surface. ...... 1100~1300kg / mm ^2, hardness ...... ...... 1300~1600kg / mm ² of depth 60μm position than the surface hardness of the depth 500μm position than the surface ...... ...... 1400kg / mm ² or more Having a hardness gradient imparts excellent heat plastic deformation, wear resistance, and toughness. The coated tool is characterized in that the life of the tool is further extended by improving the strength with the intermediate layer interposed and reducing the decrease in the strength due to the coating on the intermediate layer side.

[Action]

In the coated cemented carbide tool of the present invention, the reason why the hardness gradients of the coating layer and the intermediate layer are limited as described above as the desirable range will be described below.

Coating layer Titanium carbonitride and titanium nitride coating by chemical vapor deposition is performed in a mixed gas consisting of titanium tetrachloride, hydrogen, organic CN compound and / or nitrogen, and the partial pressure of the organic CN compound is less than that of titanium tetrachloride. It is suitable that the pressure is made low and the hydrogen partial pressure is 1/10 or less.

When the titanium carbonitride coating is applied to the intermediate layer of the cemented carbide substrate with the binder phase enriched on the surface under the above conditions, the diffusion of carbon is small due to the low coating temperature and the decarburized layer is hard to form. As a result, it is improved to the same level as the substrate.

Intermediate layer (a) Surface hardness If the hardness is less than 900 kg / mm ² , it is good in terms of toughness improvement, but plastic deformation resistance is significantly deteriorated, while if the hardness exceeds 1100 kg / mm ² , It is impossible to prevent crack propagation in the hard layer, and the strength of the tool becomes insufficient, so that 900 to 1100 kg / mm ²
And

(B) Hardness at a depth of 15 to 60 μm The hardness is 1100 and 1300 kg / mm ² respectively.
If it is less than 1, the toughness is improved, but the plastic deformation resistance is significantly deteriorated.
If the hardness exceeds 00 kg / mm ² , the desired toughness cannot be ensured.
1300 kg / mm ² and 1300 to 1600 kg / m
m ²

(C) Hardness at 500 μm position It is considered that the part that has the greatest effect on improving the toughness of the tool is the range up to a depth of about 100 μm from the surface of the cemented carbide substrate. Rather influences the improvement of plastic deformation resistance, and the hardness at this depth position is determined according to the purpose of use of the tool, and the lower limit of the hardness at 500 μm position is set as the plastic deformation resistance. It was 1400 kg / mm ² which can be secured.

This will be described in detail below with reference to examples.

Example 1. A chip (SNM432) having a composition of 75.5% tungsten carbide, 5% titanium carbide, 0.5% titanium nitride, 10% tantalum carbide, and 9% cobalt (above wt%) was vacuumed to 2 × 10 ^-2. In a vacuum of torr, the sintering temperature was maintained at 1400 ° C. for 60 minutes for sintering, and then cooled at a cooling rate of 0.05 ° C./min to produce chips. When observing the cross-sectional structure of the surface portion of the chip,
Surface 1050 kg / mm ² in both Vickers hardness, depth 15μm position 1260 kg / mm ^2, the depth 60μm position 1520kg / mm ² and a depth 500μm position 1540k
A hardness gradient of g / mm ² was exhibited, and the amount of bound metal decreased as the depth became deeper than the surface. On the other hand, for the purpose of comparison, a chip manufactured in the same manner as in the above example except that it was not cooled was 1520 kg / mm ^{2 in} hardness near the surface and 500 μ in depth.
There was no change at the m position of 1540 kg / mm ² .

Organic C for chips with this intermediate layer and for comparative chips
A reaction temperature of 850 ° C. by a chemical vapor deposition method using an N compound,
Reaction formula 2TiC ₄ + 2R · CN + 3H ₂ → 2Ti (CN) +6
A TiCN film having a film thickness of 8 μm was deposited on the basis of HC + 2R · C. Also, the reaction temperature was 1030 ° C. and the reaction formula was 2TiC ₄ + 2CH ₄ + N ₂ + H ₂ → 2TiCN + 8HC by chemical vapor deposition.
A TiCN film having a film thickness of 8 μm was vapor-deposited on the basis of 1 + H ₂ . Next, regarding the above-mentioned chip of the present invention and the comparative chip, the work material: SNCM-8 (HS50) (with 4 grooves) cutting speed; 120 m / min feed amount; 0.3 mm / rev cutting time; 10 min number of chips; 10 pieces An intermittent cutting test was performed under the conditions.

The chip of the present invention is 1/10, the comparative chip of the chemical vapor deposition method using the organic CN compound without the intermediate layer is 5/10, and the comparative chip has the intermediate layer, and the comparative chip of the chemical vapor deposition method using CH ₄ gas and N ₂ gas is 4 chips. The comparative chip of the chemical vapor deposition method using the CH ₄ gas and the N ₂ gas without the intermediate layer showed 6/10 defects. The influence of the chemical vapor deposition method on the strength is also a considerable factor, and it is clear that the chip of the present invention has superior impact resistance as compared with the other three examples.

Further, using the above chips, a continuous longitudinal cutting test was carried out under the following conditions: Work material: SNCM-8 (HS50) Cutting speed: 200 m / min Cutting depth: 1.5 mm Feed rate: 0.3 mm / rev.

The chip of the present invention showed normal wear at VB = 0.25 mm after cutting for 30 minutes, whereas the comparative chip of the chemical vapor deposition method using the organic CN compound without the intermediate layer showed VB = 0.30 after cutting for 30 minutes.
Burrs were observed because part of the coating fell off at 23 mm.
The comparative chip, which has an intermediate layer and is compared with the chemical vapor deposition method using CH ₄ gas and N ₂ gas, has a life of VB = 0.45 mm after cutting for 30 minutes because of chipping accompanied by chipping. A burr was observed in the comparative chip of the chemical vapor deposition method using the CH ₄ gas and the N ₂ gas without the intermediate layer, because VB = 0.40 mm after cutting for 30 minutes and a part of the film fell off. The effect of chemical vapor deposition on wear resistance is PV
There is no difference between the D method and the CVD method, and it is clear that the chemical vapor deposition method using titanium tetrachloride and the organic CN compound has the same excellent wear resistance.

Example 2 Tungsten carbide 71%, titanium carbide 9%, titanium nitride 0.5%, tantalum carbide 10%, cobalt 9.5%
A chip (SPC432) having an alloy composition equivalent to JIS P30 consisting of (above wt%) is 2 × 10 ^-2 vacuum degree.
Sintering temperature was maintained at 1400 ° C. in vacuum for 60 minutes for sintering, and then cooled at a cooling rate of 0.05 ° C./min to produce chips. Observation of the cross-sectional structure of the surface of the above chips showed that the surface had a Vissoth hardness of 950 kg.
/ M m ² , depth 15 μm position 1150 kg / m m ² , depth 6
Shows the hardness gradient of 0μm position 1480kg / mm ² and a depth 500μm position 1430kg / mm ^2, the amount of bound metal had become less as they become deeper than the surface. On the other hand, for the purpose of comparison, the chips manufactured in the same manner as in the above example except that they were not cooled did not change the hardness near the surface to 1460 kg / m ² and the depth of 500 μm to 1430 kg / mm ² .

The chip having the intermediate layer thus obtained and the comparative chip were subjected to a chemical vapor deposition method at a reaction temperature of 850 ° C. and a reaction formula of 2TiC ₄ + 2R / CN + 3H ₂ → 2Ti (CN) +6.
A TiCN film having a thickness of 2 μm was deposited on the basis of HC + 2RC. Film thickness 2
The reason for selecting μm is that sufficient strength is required for milling. The reaction temperature is 1030 by the chemical vapor deposition method.
℃, reaction formula 2TiC ₄ + 2CH ₄ + N ₂ + H ₂ → 2Ti (CN) + 8H
A TiCN film having a film thickness of 2 μm was deposited on the basis of C + H ₂ . Next, regarding the above-described tip of the present invention and the comparative tip Work material: SCM440 (HS50) Cutting speed: 100 m / min Feed rate: 0.5 mm / rev Cutting time: 10 min Cutter; DP (corner angle 25 °) Number of tips: 10 pieces The milling test was carried out under the conditions.

The chip of the present invention is 0/10, the comparative chip of the chemical vapor deposition method using an organic CN compound without the intermediate layer is 2/10, and the comparative chip of the chemical vapor deposition method with the CH ₄ gas and the N ₂ gas is 8 / 10 chips, the comparative chips of the chemical vapor deposition method using CH ₄ gas and N ₂ gas without the intermediate layer showed 7/10 defects. It is clear that the chip of the present invention has excellent impact resistance, although chipping due to impact caused by biting of the cutting edge such as a milling cutter includes more complicated factors than turning.

Further, using the above chips, a life test was carried out under the following conditions: Work material: SCM440 (HS50) Cutting speed: 200 m / min Cutting depth: 1.5 mm Feed rate: 0.2 mm / rev.

The chip of the present invention showed normal wear after cutting for 60 minutes, whereas the comparative chip of the chemical vapor deposition method using the organic CN compound without the intermediate layer showed burrs because a part of the coating film fell off after cutting for 60 minutes. . The comparative chip having the intermediate layer and using the chemical vapor deposition method using CH ₄ gas and N ₂ gas reached the end of its life due to chipping and chipping after 10 minutes of cutting. A comparison chip of the chemical vapor deposition method using CH ₄ gas and N ₂ gas titanium tetrachloride without an intermediate layer had a part of the film dropped off from the beginning and was chipped after cutting for 5 minutes.
The effect of chemical vapor deposition on wear resistance and impact resistance is PVD
The chemical vapor deposition method using an organic CN compound has the same excellent impact resistance as PVD and at the same time has the same resistance as the PVD method and the CVD method. It is clear that it has performance similar to CVD in terms of wear and adhesion.

〔The invention's effect〕

The coated cemented carbide tool of the present application has an excellent impact resistance and chipping resistance by providing an intermediate layer on the surface and reducing the decarburization layer by low temperature chemical vapor deposition, and shows a stable and long tool life as a tool. is there.

Claims (1)

[Claims] 1. A surface of a cemented carbide substrate made of an iron group metal and one or more kinds of carbides, carbonitrides and nitrides of groups 4a, 5a and 6a of the periodic table of elements, and In a method for producing a cemented carbide, which has a toughness and is softer than that of the cemented carbide substrate, and an intermediate layer having a hardness gradient in which the hardness continuously increases toward the cemented carbide substrate is interposed. A layer consisting of one or more of 4a, 5a and 6a carbides, carbonitrides, nitrides, oxides, oxycarbides, oxynitrides, oxycarbonitrides and aluminum oxides of group 4a, 5a and 6a In addition, the vapor deposition method is a single-layer or double-layer method using both a medium temperature chemical vapor deposition method in which a coating treatment is performed at 700 ° C. to 900 ° C. using an organic CN compound as a reaction gas and a high temperature chemical vapor deposition method in which a coating treatment is performed at 950 ° C. to 1050 ° C. 1-20 micron coating layer Method for producing a coated cemented carbide tool, characterized in that the.