JPS6120628B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coated cemented carbide component whose performance as a cutting tool material is further improved.

In recent years, WC has been used as the main component, and if necessary,
The base material is a cemented carbide component in which a hard material containing multiple carbides of Ti, Nb, Ta, and W is bonded mainly with Co, and the surface is coated with a 1-20μ thin layer of wear-resistant TiC etc. Since coated cemented carbide parts have both the toughness of the base material and the wear resistance of the surface, they are widely used as an excellent cutting tool material in place of conventional cemented carbide parts.

On the other hand, in recent years, the depletion of nonferrous metal resources has become a problem worldwide, and W, which is one of the raw materials for cemented carbide parts, is a scarce resource.
Measuring this has become a very important consideration in the cemented carbide parts manufacturing industry.

From this point of view, it belongs to Group A of the periodic table, the same as W, and is more endowed with resources than W.
Research has already been conducted on replacing part or all of W with Mo, and this was also proposed in Japanese Patent Application Laid-Open No. 146303/1983.

The gist of this proposal is that while the conventional carbide of W is a monocarbide represented by the chemical formula WC, the carbide of Mo is a lower carbide represented by the chemical formula Mo ₂ C. It is stable, but compared to WC, hardness, elastic modulus,
Because of its poor thermal conductivity, it is not suitable as a hard material for cemented carbide parts, so some of the W in WC was replaced with Mo (Mo _x W _1-x )C (where x is 0<
If we were to synthesize a monocarbide represented by the chemical formula x < 1), this monocarbide would have the same crystal structure as WC, so unlike Mo ₂ C, would it be suitable as a hard substance for cemented carbide parts? .

On the other hand, the present inventors conducted a detailed study on the cutting phenomena of coated cemented carbide parts, and found that the primary cause of tool wear when actually cutting coated cemented carbide parts is:
We obtained the knowledge that this is due to plastic deformation of the tool cutting edge, and that the primary cause of damage to the tool cutting edge (so-called chipping) is thermal cracking caused by thermal stress caused by the temperature gradient generated within the tool.

Therefore, as a base material for coated cemented carbide parts, it must have high hardness at high temperatures and high elastic modulus to reduce plastic deformation, and high thermal conductivity to prevent temperature gradients from forming inside the tool. It can be understood that the following two points need to be satisfied.

Therefore, a cemented carbide part made of the above-mentioned double carbide of Mo and W as a hard substance (hereinafter abbreviated as Mo-based cemented carbide)
is considered to be sufficiently practical as a base material for coated cemented carbide parts, and the same content is disclosed in JP-A-51-146306.

However, the present inventors actually followed this idea and used Mo-based carbide as a base material to produce TiCl ₄ , CH ₄ ,
When TiC was coated with 5 μm of TiC at approximately 1000°C in a mixed gas flow of H ₂ , a large amount of lower carbide, which was thought to be the (Mo _x W _1-x ) ₂ C phase, was found up to a depth of approximately 30 μ from the surface of the substrate. This was proven by the fact that when this coated cemented carbide part was actually cut, the TiC coating layer immediately peeled off, significantly impairing the cutting properties.

This is because (Mo _x W _1-x ) in the base material is obtained from the gas phase when forming TiC, but the (Mo x W 1-x ) in the base material is expressed as follows: 2 (Mo _x W _1-x )C→(Mo _x W _1-x ) ₂ C+C ……(1) This is thought to be because C generated during decomposition is mainly consumed.

This phenomenon also occurs when cemented carbide parts with WC as a hard substance are used as a base material, as 3WC + 3Co → W ₃ Co ₃ C + 2C ...(2) is caused by consuming C in the formation of TiC. It is known that a double carbide of W and Co called the η phase is formed at the material interface, and this η phase is extremely brittle and consumes the binder phase metal Co, which significantly impairs toughness. In the hard metal industry, how to prevent the formation of this η phase is even considered to be the most important point in producing coated cemented carbide parts.

When Mo-based carbide is used as a base material, (Mo _x W _1-x ) ₂ C is soft, half the hardness of (Mo _x W _1-x )C,
Furthermore, since no binder phase metal is consumed when forming (Mo _x W _1-x ) ₂ C, at first glance it seems that the decrease in toughness is less than when conventional cemented carbide parts are used as the base material. In fact, from a thermodynamic point of view, the reaction (1) is considered to occur very easily at the high temperature of about 1000℃ when coating TiC by chemical vapor deposition, and the It is thought that almost all of the (M _x W _1-x )C contained within is decomposed into (M _x W _1-x ) ₂ C.

Therefore, the difference in mechanical properties between the (Mo _x W _1-x ) ₂ C-only part near the base material interface and the other parts is too large, so when actually cutting with this coated cemented carbide part, In the (Mo _x W _1-x ) ₂ C-enriched layer, a collapse phenomenon occurs near the boundary with other parts, and as a result,
It is thought that the TiC coating layer peeled off.

Therefore, in order to manufacture coated cemented carbide parts using Mo-based carbide as a base material, it is important to find a way to suppress the amount of (Mo _x W _1-x ) ₂ C that precipitates at the interface of the base material. It will be done.

Conventionally, in cemented carbide parts that use WC as a hard material, the simplest solution to this problem is to reduce the brittleness of the base material surface by coating it with a nitride of a transition metal element in group a of the periodic table. It is known to prevent

However, in coated cemented carbide parts coated with nitrides of transition metal elements of Group A of the Periodic Table, C in the base material hardly participates in the formation of the coating film.
Due to the poor adhesion strength between the coating film and the base material, nitrides are rarely put into practical use despite their excellent crater resistance, and in reality TiC is coated directly onto the base material of cemented carbide parts. Later, methods were used in which TiN was coated or Ti(CN) was coated in between.

Chemical vapor deposition uses explosive gases such as H ₂ and CH ₄ ,
Since the process involves handling corrosive substances such as TiCl ₄ , the manufacturing equipment is necessarily expensive.
Double coating of TiN/TiC or TiN/Ti(CN)/
It is clear that a triple coating of TiC would be much more complex and expensive to perform.

Therefore, based on the knowledge that the reaction of formula (1) shown above is much more likely to occur in Mo-based carbide than in cemented carbide parts using conventional WC as a hard material, the present inventors If the surface of the base material is coated with a transition metal element of group a of the periodic table by chemical vapor deposition, a small amount of (Mo _x W _1-x )C near the interface of the Mo-based carbide base material. It decomposes according to Equation (1) of Hasaki, and the resulting C is consumed in forming the coating film.

In other words, the coating film in the part that is in direct contact with the base material automatically becomes TiC or Ti(CN), and the diffusion rate of C in TiC or Ti(CN) is very slow compared to that in the binder phase metal, so it remains constant. Above the thickness of
By coating TiN, TiN/
We came up with the idea that it would be possible to realize a Ti(CN) and/or TiN/TiC double coating.

_In addition, in this case _, the _large amount of precipitation of (Mo The amount of ( _Mo x W _1-x ) ₂ C is only slightly enriched compared to other parts, and this (Mo _x W _1-x ) ₂ C-enriched layer has lower hardness than other parts, but the coating super A proposal was made that cutting characteristics would be dramatically improved if the hardness of hard metal parts at a depth of 10 to 200μ below the base material surface was reduced by 2 to 20% in terms of Pickers hardness (Japanese Patent Laid-Open No. 52-110209
Considering the above (No. 1), a slight enrichment of (Mo _x W _1-x ) ₂ C is considered to be preferable. Based on this idea, the present inventors actually produced a prototype, and the expected effects were observed.

Note that when coated with nitride such as TiN, TiC
The flank wear resistance is slightly inferior to that of carbides such as TiC, but this is due to the difference _in high temperature hardness between TiN and _TiC . _ZrO2 0.1~10
If it is less than 0.1μ, it is difficult to obtain an effect, and if it is more than 10μ, it is preferable from the viewpoint of deterioration of toughness.

However, if the coating thickness of a nitride such as TiN is less than 1 μm, the coating effect will be poor, and if it is more than 20 μm, the ratio of nitrides to carbides in the coating film will be significantly biased towards nitrides, resulting in poor double coating effect. Therefore, 1 to 20μ
is preferred.

In addition, as Mo-based cemented carbides, in addition to double carbides of Mo and W, double carbonitrides of Mo and W are used as hard substances, and as necessary, groups a, group a of the periodic table, etc.
It is also effective to use in combination one or more carbides and/or carbonitrides of transition metal elements of group a.

In addition, the binder phase metals include Cr, Mo, W, Fe,
A material whose main component is one or more selected from the group consisting of Co and Ni may be used. As the coating material, in addition to nitrides of one or more transition metal elements of group a of the periodic table, nitrides of various transition metal elements such as TaN and Si ₃ N ₄ can be used with similar effects.

The present invention will be explained in detail below using examples.

Example 1 (Mo _0.7 W _0.3 ) C92 weight % ₍ however, the ratio of Mo and W is the atomic ratio ₎ , Ni 4 weight %, and Co 4 weight % were weighed out and made into a product with model number SNMG432ENZ using a normal powder metallurgy method. created a chip. This chip was coated with TiCl ₄ , N ₂ , and H ₂ at 950° C. using a conventional chemical vapor deposition method.

After cooling, the chip was cut and examined with a metallurgical microscope, and the coating film contained approximately 3μ of TiN on the outside and about 3 μm of TiN on the inside.
It was found that the layer thought to be TiC was coated with a total thickness of 3μ and 6μ, and that about 30μ from the base material interface was slightly enriched in (M _x W _1-x ) ₂ C than the other parts. This chip is referred to as A, and for comparison, the same substrate coated with 6μ of TiC is referred to as B, a commercially available K-10.
C, which is a cemented carbide part coated with 6 μm of TiN.
D, TiC coated with 3μ of TiN and 3μ of TiC
These are the workpiece material S50C forged material (50mmφ×300mm
) Cutting speed: 120 m/min Feed: 0.28 mm/rev Cutting depth: 1 mm to 3 mm When cutting tests were conducted under cutting conditions (1) of 1 mm to 3 mm, A was able to cut 34 pieces, whereas B was due to chipping of the cutting edge due to peeling of the coating layer. Only 2, same as C
Only 12 pieces could be cut, D could cut 33 pieces, and E could only cut 25 pieces due to crater wear. In addition, cutting tests were conducted on chips A to E above under cutting conditions (2): work material: FC25, cutting speed: 200 m/min, feed: 0.36 mm/rev, depth of cut: 2 mm, cutting time: 5 minutes.
0.19mm, D also showed normal flank wear of 0.19mm, and E showed normal flank wear of 0.15mm, whereas B chip had severe tipping at the cutting edge and had a maximum flank wear of 0.82mm, and C also showed maximum flank wear of 0.49mm. .

Example 2 Chip A prepared in Example 1 was coated with chemical vapor deposition.
Covered with 1μ of Al ₂ O ₃ and cut under the cutting conditions (2) of Example 1.
After cutting for 20 minutes, normal flank wear was 0.21 mm.

Example 3 Chip A of Example 1 was coated by chemical vapor deposition.
F was coated with 2 μ of ZrO ₂ , G was coated with 5 μ, and H was coated with 12 μ. Cutting was performed for 10 minutes under the cutting conditions (2) of Example 1, and F showed normal flank wear of 0.14 mm. In comparison, G exhibited a slight chipping of the cutting edge and maximum flank wear of 0.31 mm, and H could only cut for 19 seconds due to damage to the cutting edge.

Example 4 (Mo _{0.7 W 0.3} ) C82% by weight _, (Ti, Nb, Ta,
Weigh out 10% by weight of W) (CN), 4% by weight of Ni, and 4% by weight of Co, and use the normal powder metallurgy method to create a model number.
Created TNMG432ENZ.

This chip was heated in a mixed gas flow of TiCl ₄ , N ₂ , and H ₂ .
Three types of coating were performed at 980°C for 10 hours, 5 hours, and 2 hours. After cooling, the coating thickness was measured using a β-scope (trade name of a coating thickness measuring device manufactured by Fischer) and found to be 22μ, 14μ, and 7μ, respectively. Cutting conditions (3) Work material SCM3 plate material (50mm×150mm×450
mm) Cutting speed: 120m/min, feed: 0.22mm/rev, depth of cut: 2mm As a result of cutting tests, the cutting edge of the 7μ coated one was not damaged even after cutting for 5 minutes, but the 14μ
There is some chipping on the cutting edge of the 22μ
The coated material could only be cut for 23 seconds due to tipping.

Example 5 The same base material as in Example 4 was coated with 5μ of ZrCl ₄ , N ₂ , and H ₂ at 1020°C in a mixed gas flow.
J is the one coated with 5μ of HfCl ₄ , N ₂ , H ₂ at 1030°C in a mixed gas flow, and K is the one coated with 5μ of TiC for comparison, and these three were subjected to the cutting conditions (3) of Example 4. As a result of a cutting test, both I and J could be cut for 3 minutes, but K could not be cut after 1 minute and 12 seconds due to tipping.

Claims (1)

[Claims] 1 Mo and W double carbides and/or double carbonitrides are used as hard substances, and one or more transition metal elements selected from the group consisting of Cr, Mo, W, Fe, Co, and Ni The base material is a cemented carbide component bonded by a method of bonding, and the cemented carbide component base material is composed of Mo and W double carbides and/or double carbonitrides (Mo _x The amount of W _1-x ) C ₂ and/or (Mo _x W _1-x ) ₂ (CN) (where x is 0<x<1) is larger than that in other parts of the base material, and the amount of The surface of the material is coated with 1 to 20μ of one or more nitrides of Group A transition metal elements of the periodic table by chemical vapor deposition, and the carbon content inside the coating layer is higher than the outside. A coated cemented carbide part characterized by: 2. A cemented carbide made of Mo and W double carbide and/or double carbonitride as a hard substance, combined with one or more transition metal elements selected from the group consisting of Cr, Mo, W, Fe, Co, and Ni. The cemented carbide component base material contains Mo and W double carbides and/or double carbonitrides (Mo _x W _1-x ) ₂ at a depth of 10 to 200 μ from the surface. and/or the amount of (Mo _x W _1-x ) ₂ (CN) (where 0<x<1) is
larger than the other parts of the base material, and after coating the surface of the base material with 1 to 20 μm of nitride of one or more transition metal elements of group a of the periodic table by chemical vapor deposition,
A coated cemented carbide part characterized in that the surface thereof is further coated with 0.1 to 10μ of Al ₂ O ₃ and/or ZrO ₂ . 3. A double carbide and/or double carbonitride of Mo and W and one or more carbides and/or carbonitrides of Group A, Group A, and Group A transition metal elements of the periodic table are used as hard substances, Cr, Mo, W, Fe, Co,
The base material is a cemented carbide component bonded with one or more transition metal elements selected from the group consisting of Ni, and the cemented carbide component base material contains Mo and W at a depth of 10 to 200 μ from the surface. Among double carbides and/or double carbonitrides, the amount of (Mo _x W _1-x ) ₂ C and/or (Mo _x W _1-x ) ₂ (CN) (0<x<1) is
The surface of the substrate is coated with 1 to 20μ of one or more nitrides of Group A transition metal elements of the periodic table by chemical vapor deposition, and the coating layer is larger than other parts of the substrate. A coated cemented carbide part characterized by having a higher carbon content on the inside than on the outside. 4. A double carbide and/or double carbonitride of Mo and W, and one or more carbides and/or carbonitrides of Group A, Group A, and Group A transition metal elements of the periodic table as hard substances, Cr, Mo, W, Fe, Co,
The base material is a cemented carbide component bonded with one or more transition metal elements selected from the group consisting of Ni, and the cemented carbide component base material contains Mo and W at a depth of 10 to 200 μ from the surface. Among double carbides and/or double carbonitrides, the amount of (Mo _x W _1-x ) ₂ C and/or (Mo _x W _1-x ) ₂ (CN) (where x is 0<x<1) is , which is larger than other parts of the base material, and after coating the surface of the base material with 1 to 20μ of nitride of one or more transition metal elements of group A of the periodic table by chemical vapor deposition, 0.1~10μ of Al ₂ O ₃ and/or on the surface
or coated cemented carbide parts characterized by being coated with _ZrO2 .