CN103173761B - Cutting tool improving coating structure and preparation method thereof - Google Patents

Abstract

The invention discloses a cutting tool with improved coating structure, which comprises a substrate and a coating covering the substrate. The coating contains an inner layer B, a transition layer C and an outer layer D from the inside to the outside; the inner layer B is composed of transition elements Composed of compound materials composed of non-metallic materials, the transition layer C includes transition layer C1 and/or transition layer C2; both transition layers C1 and C2 are mainly composed of titanium carbonitride, and the outer layer D has a single phase of α-Al ₂ O ₃ structure, the thickness of the outer layer D is d=0.5μm-4μm, and its average grain size S is 0.2μm≤S≤0.5μm. The preparation method is to firstly prepare the tool substrate, and then deposit the inner layer B, the transition layer C2, the transition layer C1 and the outer layer D sequentially on it in the same coating cycle; and then complete the production after surface treatment. The cutting tool of the invention has high hardness and good wear resistance, and has excellent cutting performance in cutting processing of materials such as steel, stainless steel and cast iron.

Description

Cutting tool with improved coating structure and preparation method thereof

technical field

The invention belongs to the field of metal cutting, in particular to a coated cutting tool and a preparation process thereof.

Background technique

Aluminum oxide coatings have been deposited on machined tools by chemical vapor deposition (CVD) for more than 20 years. The excellent wear and corrosion resistance properties of alumina are widely discussed in the literature. The CVD alumina coatings deposited on cutting tools commonly have two phases: α-Al ₂ O ₃ and κ-Al ₂ O ₃ phases. During CVD production, Al ₂ O ₃ has κ and θ in addition to stable α. Phase, CVD κ-Al ₂ O ₃ grain size is 0.5 μm ~ 1.0 μm, and generally columnar crystals, almost no dislocations and holes in κ-Al ₂ O ₃ . κ-Al ₂ O ₃ has good cutting performance when cutting steel; its disadvantage is that during cutting, due to local high temperature and high pressure formed by extrusion, κ-Al ₂ O ₃ will also change to α-Al ₂ O ₃ transformation, because α-Al ₂ O ₃ is denser than κ-Al ₂ O ₃ (3.99g/cm ³ and 3.67g/cm ³ in turn), and there is about 8% shrinkage after transformation, so that in α-Al Obvious cracks appeared in ₂ O ₃ , and the mechanical properties of the interface between α-Al ₂ O ₃ and κ-Al ₂ O ₃ deteriorated, which would lead to chipping of κ-Al ₂ O ₃ coating. Therefore κ-Al ₂ O ₃ is not suitable for cutting at high speed and high efficiency. Therefore modern tool coatings are preferably α-Al ₂ O ₃ .

α-Al ₂ O ₃ is commonly known as corundum. It is a stable oxide with good high temperature stability, oxidation resistance, high hardness, and wear resistance. However, CVD α-Al ₂ O ₃ is generally equiaxed and the grains are much larger than κ-Al ₂ O ₃ is so large that it passes through the entire coating, and the grain size is between 1 μm and 6 μm according to the thickness of the coating. Experiments have proved that α-Al ₂ O ₃ can nucleate on the surface of Ti ₂ O ₃ and the interface of (Ti, Al)(C, O), or use CO/CO ₂ mixed gas to control the oxidation potential of the deposition atmosphere to make α- Al ₂ O ₃ nucleation. The basic concept in all these methods is that only κ-Al ₂ O ₃ can be produced on the surface of TiC, TiN, TiCN, TiCNO with fcc structure. In many prior art products, the deposited α-Al ₂ O ₃ layer is at least partially formed from κ-Al ₂ O ₃ through phase transformation when the nucleation cannot be fully controlled. This α-Al ₂ O ₃ layer consists of coarse grains with transformation cracks. Compared with the α-Al ₂ O ₃ layer composed of microcrystalline α-Al ₂ O ₃ , the mechanical properties of this are greatly reduced. Therefore, it is necessary to improve the existing technology to control the nucleation and growth of the α-Al ₂ O ₃ layer and obtain the α-Al ₂ O ₃ coating with a desired structure.

The control of polycrystalline α-Al ₂ O ₃ in industry began at the end of the 20th century, such as the use of (Al _x Ti _y )(O _w C _z ) y:x=2~4, z:w=0.6~ 0.8 modified layer Deposit κ-Al ₂ O ₃ coating on the surface of α-Al ₂ O ₃ layer. The subsequent CVD α-Al ₂ O ₃ deposition techniques all use controlled nucleation to obtain α-Al ₂ O ₃ with a specific preferred growth orientation. For example, ZL93121032.1 discloses a coated tool, which is at least partially coated with one or more layers of refractory layer, at least one layer of which is aluminum oxide, and the thickness of the aluminum oxide layer is d=0.5 μm to 25 μm, and Composed of a single-phase α-structure, its grain size (s) is: 0.5μm<S<1μm (for 0.5μm<d<2.5μm) and 0.5μm<S<3μm (for 2.5μm<d<25μm) , for the (012) growth direction of the isocrystalline plane, the structure factor of the aluminum oxide layer is greater than 1.3 (preferably 1.5).

ZL94119184.2 discloses a coated tool having a tool body with a thick coating of <20 μm, said coating comprising at least one aluminum oxide layer with a thickness of 1-10 μm, which is substantially free of cooling cracks. The coating contains at least one aluminum oxide layer, and the aluminum oxide layer is composed of single-phase α-Al ₂ O ₃ textured in the (110) direction, and its texture coefficient is greater than 1.5. The aluminum oxide layer includes flaky grains with a length of 2 μm-8 μm and a length/width ratio of 1-10.

ZL95191221.6 discloses an oxide-coated tool, which is at least partially coated with one or more layers on the tool substrate, at least one layer of which is a refractory layer of aluminum oxide, and the thickness of the aluminum oxide layer is 0.5-25 μm. The grain size (s) is: 0.5μm<S<1μm (for 0.5μm<d<2.5μm) and 0.5μm<S<4μm (for 2.5μm<d<25μm), but it has texture in the (104) direction The structure is composed of unidirectional α-structure, and the texture coefficient is greater than 1.5 (preferably 2.5, 3.0).

These several patents control the oxidation potential of the hydrogen carrier gas before α-Al ₂ O ₃ nucleation (water below 20PPM, preferably below 5PPM water), and control the process of α-Al ₂ O ₃ nucleation The reaction gas is fed into the sequence, and the alumina coatings with (012), (110), (104) growth textures are respectively obtained; ZL96110196.2, CN96100514.9 and other patents also disclose Or (104) growth textured alumina coated tool.

US20070099029 adopts a TiAlCNO intermediate layer with an Al% content increasing toward the surface, and the intermediate layer is surface-modified by an aluminum-containing gas pulse treatment plus _CO2 oxidation treatment to prepare a strong (012) layer with complete control over nucleation and growth. Growth textured α-Al ₂ O ₃ coating, the coating is composed of columnar α-Al ₂ O ₃ crystals with a texture coefficient TC(hkl) of 2.5 to 3.5 in (012) and (024). The reflections are (012)(104)(110)(113)(024)(116), and TC(104)(110)(113)(116) is less than 0.4.

US20060199026, 20060115662, US20070104945, US200601412271 and other patents are prepared by optimizing the surface modification process and parameters of the surface of the TiAlCNO intermediate layer with Al% content increasing towards the surface by using aluminum-containing gas pulse treatment and oxygen-containing gas oxidation treatment. α-Al ₂ O ₃ coatings with strong (104), (110), (006), (116) growth textures were obtained.

It is well known that the hardness of polycrystalline materials (including coatings) generally obeys the Hall-Petch formula: Where H is the hardness of the polycrystalline material, H° is the hardness of the single crystal material, C is the material constant, and d is the grain size. It can be seen from the formula that the hardness of the material can be improved by reducing the grain size of the coating. However, when dealing with nanomaterials with very small grain sizes, the effect of the increased proportion of grain boundaries in the material must be considered. Many studies have shown that an inverse Hall-Petch relationship is found when dealing with nanocrystalline hard materials with very small grain sizes. It can be clearly seen in US6472060 that when the grain size is reduced to the nano-grain region, even if the room temperature hardness is increased, the performance of crater wear resistance is also reduced. This can be explained by the increased amount of grain boundary slip. Therefore, when considering improving the wear resistance of the coating by refining the grains, the grain size should be kept above the nano grains.

To sum up, all existing technologies use the transition layer technology to control the nucleation of α-Al ₂ O ₃ to obtain α-Al ₂ O ₃ coatings with specific growth textures, while directly affecting the α-Al 2 O 3 The grain size of the microhardness and wear resistance of the ₂ O ₃ coating has not been thoroughly studied and described, and the influence of the grain size of the α-Al ₂ O ₃ coating on the performance of the coating and the coating tool has not been considered comprehensively . It is necessary for us to further adjust, combine and design the coating microstructure of cutting tools to improve the hardness, wear resistance and stability of the coating.

Contents of the invention

The technical problem to be solved in the present invention is to overcome the deficiencies in the prior art, to provide a cutting tool with high hardness, good wear resistance and improved coating structure and its preparation process. The cutting tool of the present invention can be used on steel, stainless steel, cast iron, etc. It has excellent cutting performance in material cutting.

In order to solve the problems of the technologies described above, the present invention proposes the following technical solutions:

A cutting tool for improving the coating structure, comprising a substrate A (the coating substrate can be materials such as cemented carbide, cermet, non-metal ceramic, PCD or CBN) and a coating at least partially covered on the substrate A, said The coating consists of inner layer B, transition layer C and outer layer D from inside to outside;

The inner layer B is mainly composed of compound materials composed of transition elements and non-metallic elements in the periodic table of elements, and the transition elements are selected from at least one of group IVB, group VB, and group VIB in the periodic table of elements. The non-metallic element is selected from at least one of carbon, nitrogen, oxygen, and boron;

It is characterized in that the transition layer C includes a transition layer C1 and/or a transition layer C2 from outside to inside;

The transition layer C1 is mainly composed of titanium carbonitride TiC _x1 N _y1 O _z1 , and the x1, y1, and z1 respectively represent the atomic percentages of C, N, and O in TiC _x1 N _y1 O _z1 , and satisfy 0.5≤ z1/(x1+y1+z1)≤1, y1≤x1≤z1;

The transition layer C2 is mainly composed of titanium carbonitride TiC _x2 N _y2 O _z2 , and the x2, y2, and z2 respectively represent the atomic percentages of C, N, and O in TiC _x2 N _y2 O _z2 , and satisfy 0.5≤ x2/(x2+y2+z2)≤1,

The outer layer D has a single-phase α-Al ₂ O ₃ structure, the thickness of the outer layer D is d=0.5 μm˜4 μm, and its average grain size S is 0.2 μm≤S≤0.5 μm.

In the above-mentioned cutting tool with improved coating structure, in the transition layer C1, the x1, y1, and z1 preferably satisfy 0.5≤z1/(x1+y1+z1)≤0.8; the transition layer C1 is preferably flaky or Granular nanocrystalline structure, the grain size of the transition layer C1 is preferably less than 200 nm, and the thickness of the transition layer C1 is preferably less than 0.5 μm.

In the above-mentioned cutting tool with improved coating structure, in the transition layer C2, the x2, y2, and z2 preferably satisfy 0.8≤x2/(x2+y2+z2)≤1 (more preferably, the x2=1, y2=0, z2=0, that is, the transition layer C2 is a TiC coating.); The transition layer C2 is preferably a discretely distributed nano-equiaxed particle structure, and the grain size of the transition layer C2 is preferably less than 200nm. The thickness of the transition layer C2 is less than 0.5 μm (more preferably less than 0.3 μm).

In the above-mentioned cutting tool for improving the coating structure, the compound material of the inner layer B is preferably selected from one of carbides, nitrides, borides, oxides, carbonitrides, boronitrides, borocarbonitrides or multiple, at least one of the compound materials has a columnar or fibrous crystal structure. More preferably, the inner layer B comprises a layer of MT-TiCN with a thickness greater than 3 μm.

In the above-mentioned cutting tool with improved coating structure, the total thickness of the transition layer C is preferably in the range of 0.1 μm to 0.8 μm.

As a further improvement to the above-mentioned cutting tool for improving the coating structure, a Ti-containing compound marking layer E is coated on the outside of the outer layer D, and the marking layer is preferably TiN or TiCN. The Ti-containing compound marking layer The thickness is preferably 0.1 μm to 1 μm.

As a general technical idea, the present invention also provides a method for preparing the above-mentioned cutting tool with improved coating structure, comprising the following steps: first prepare the tool substrate of cemented carbide, cermet, non-metal ceramic, PCD or CBN material , the following coatings are then deposited on the tool substrate in the same coating cycle:

(1) Deposit the above-mentioned inner layer B on the tool substrate A by conventional CVD method;

(2) Depositing the above-mentioned transition layer C2 on the inner layer B using a conventional HT-CVD process;

(3) Depositing the above-mentioned transition layer C1 on the transition layer C2 by conventional HT-CVD method;

(4) depositing the above-mentioned outer layer D on the transition layer C1 by conventional HT-CVD method;

(5) adopt sand blasting or silicon-containing nylon brush polishing to carry out surface treatment to above-mentioned obtained cemented carbide coating blade;

(6) Utilize the conventional CVD method to deposit one layer of the above-mentioned Ti-containing compound marking layer on the outer layer D; Remove the aforementioned marking layer to expose the outer layer B to complete the fabrication.

As a further improvement to the above preparation method, the deposition of the outer layer D refers to optimizing the nucleation of the transition layer C1 using a mixed gas of CO, CO ₂ and H ₂ S on the transition layer C1, and then on the outer layer D After alumina nucleation, use H ₂ S or SF ₆ to optimize the growth of alumina coating to obtain the fine-grained α-Al ₂ O ₃ structure; the deposition process of the outer layer D is controlled at 900 ℃～1020℃ temperature range.

Compared with the prior art, the present invention has the advantages of:

1. The outer layer D of the cutting tool of the present invention is designed to have a single-phase α-Al ₂ O ₃ ultra-fine-grained oxide coating of the structure, preferably a pure α-Al ₂ O ₃ coating, the thickness of the coating It is d=0.5μm～4μm, and its grain size S is 0.2μm≤S≤0.5μm. The grain size design of the outer layer D is combined with the improved coating structure of the present invention, which makes the cutting tool of the present invention have excellent oxidation resistance and crater wear resistance. The present invention limits the grain size of the outer layer α-Al ₂ O ₃ through optimization, which not only further improves the uniformity, hardness and wear resistance of the surface layer α-Al ₂ O ₃ coating, but also avoids the A reverse Hall-Petch phenomenon occurs when the particle size is too small, resulting in a decrease in hardness and wear resistance.

2. The transition layer C2 provided by the cutting tool of the present invention can effectively improve the nucleation uniformity and density of the transition layer C1, avoiding the problem of uneven distribution of a single TiO, TiCO thin layer or TiAlCO thin layer on the surface of the inner layer B At the same time, the transition layer C2 has a discretely distributed TiC nanometer equiaxed particle layer, which can improve the unevenness of the surface formed by the inner layer B during the growth process to a certain extent, and reduce the roughness of the coating; Optimizing the composition of the transition layer C2 (0.5≤x2/(x2+y2+z2)≤1) can effectively improve the degree of equiaxation of the transition layer C2; and optimizing the thickness of the transition layer C2 can avoid the crystallization of the transition layer C2. Coarsening of the grains, thereby avoiding the decrease of the grain density of the outer oxide coating, and avoiding the decrease of the coating strength and coating bonding strength.

3. The cutting tool of the present invention is also provided with a transition layer C1, by optimizing its thickness, the coarsening and abnormal growth of transition layer C1 crystal grains can be avoided, thereby obtaining a small and uniform transition layer C1, and then it can be formed by induction Nucleation, on which a uniform, high-density outer oxide coating nucleation layer is obtained; at the same time, the present invention optimizes the composition of the transition layer C1 (0.5≤z1/(x1+y1+z1)≤1 , y1≤x1≤z1), an ideal crystal structure can be obtained, for example, the transition layer C1 can control the nucleation of oxide crystals with a corundum structure, which is very important for the preparation of the outer layer of α-Al ₂ O ₃ or its doped coating Layers play an important role.

4. In the preferred cutting tool of the present invention, the outer layer is also provided with a Ti compound marking layer with a color different from that of the inner layer. This layer can be deposited by CVD or PVD, or can be coated by brushing or spraying. In order to ensure the cutting performance of the tool, the marking layer is partially or completely removed on the cutting edge, rake face or flank face.

In addition, the microstructure formed by the thin equiaxed high-carbon transition layer C2 and the thin flaky transition layer C1 in the present invention can effectively improve the nucleation density and distribution uniformity of the transition layer C1, thereby improving The nucleation density of the oxide coating with the outer α-Al ₂ O ₃ structure can refine the grains and improve the uniformity, hardness and wear resistance of the surface oxide coating. It can be seen that the transition layer with a suitable structure Helps to provide an oxide coating with the desired microstructure on the tool, which in turn improves the overall cutting performance of the tool.

Description of drawings

Fig. 1 is a schematic structural view of a cutting tool in Embodiments 1 to 4 of the present invention.

Fig. 2 is a scanning electron micrograph of the outer layer D of the cutting tool in Example 1 of the present invention (the magnifications are 10000, respectively).

3 is a scanning electron micrograph of the transition layer C1 of the cutting tool in Example 1 of the present invention (the magnifications are respectively 30000).

Fig. 4 is a scanning electron micrograph of the outer layer D of the cutting tool in Example 3 of the present invention (the magnifications are 10000, respectively).

Fig. 5 is a scanning electron micrograph (10000 magnifications, respectively) of the outer layer D of a comparative cutting tool 1 in an embodiment of the present invention.

Fig. 6 is a scanning electron micrograph (10000 magnifications, respectively) of the outer layer D of a comparative cutting tool 2 in an embodiment of the invention.

Fig. 7 is a scanning electron micrograph of the transition layer C1 of the comparative cutting tool 2 in the specific embodiment of the present invention (the magnifications are respectively 10000).

illustration:

1. Substrate A; 2. Coating; 21. Inner layer B; 22. Transition layer C; 221. Transition layer C1; 222. Transition layer C2; 23. Outer layer D.

Detailed ways

Example 1:

A cutting tool with improved coating structure of the present invention as shown in Figure 1, comprising a substrate A1 and a coating 2 at least partially covered on the substrate A1, the coating 2 includes at least an inner layer B21, a transition layer from the inside to the outside Layer C22 and outer layer D23.

in:

The inner layer B21 is mainly composed of MT-TiCN material with a thickness of 6 μm;

The outer layer D23 is mainly composed of α-Al ₂ O ₃ material, the thickness d=4μm, the outer layer D23 is an ultra-fine grain oxide coating, and the average grain size S of α-Al ₂ O ₃ in the outer layer D is 0.46 μm ;

Transition layer C22 includes transition layer C1 221 and transition layer C2 222 from outside to inside:

The transition layer C1 221 is mainly composed of titanium carbonitride TiC _x1 N _y1 O _z1 (specifically TiC _0.5 O _0.5 ), where x1, y1, and z1 respectively represent the atomic percentages of C, N, and O in TiC _x1 N _y1 O _z1 , and x1=0.5, y1=0, z1=0.5, z1/(x1+y1+z1)=0.5; the transition layer C1 is a flaky (or granular) nanocrystalline structure, the thickness of the transition layer C1 is 0.2 μm, the transition The grain size of layer C1 is less than 200nm;

The transition layer C2 222 is mainly composed of titanium carbonitride TiC _x2 N _y2 O _z2 (specifically TiC), x2, y2, z2 respectively represent the atomic percentages of C, N, and O in TiC _x2 N _y2 O _z2 , and x2 =1, y2=0, z2=0, and x2/(x2+y2+z2)=1; the transition layer C2 is a discretely distributed nanometer equiaxed particle structure, the thickness of the transition layer C2 is 0.2 μm, and the transition layer C2 The grain size is less than 200nm.

The cutting tool of the above-mentioned present embodiment is mainly prepared by the following method:

(1) Preparation of cemented carbide matrix: first use a ball mill to wet mix 10wt% Co, 12wt% Ti and Ta cubic carbonitrides, and the rest of the WC powder for 20 hours, dry the mixture, press it into a compact, and press The blank is sintered into a cemented carbide tool substrate, the surface and cutting edges of which are wet blasted; the following coatings are then deposited on said tool substrate in the same coating cycle:

(2) Deposit the above-mentioned inner layer B21 on the cutter substrate A1 by conventional CVD method;

(3) Utilize conventional HT-CVD process to deposit above-mentioned transition layer C2 222 (TiC) on inner layer B21;

(4) Depositing the above-mentioned transition layer C1 221 (TiC _0.5 O _0.5 ) on the transition layer C2 using a conventional HT-CVD process;

(5) The above-mentioned outer layer D23 (α-Al ₂ O ₃ ) is deposited on the transition layer C1 221 by the following method: the transition layer C1 is deposited before the alumina nucleation of the outer layer D; the deposition of the outer layer D23 is Refers to optimizing the nucleation of the transition layer C1 by using a mixture of CO, CO ₂ and H ₂ S on the transition layer C1, and then using H ₂ S (or SF ₆ ) to nucleate the outer layer D23 after the nucleation of alumina The growth of the alumina coating is optimized to obtain the α-Al ₂ O ₃ structure with fine grains; the deposition process of the outer layer D23 is controlled at 1000°C;

(6) Surface treatment is carried out on the hard alloy coated blade prepared above by sand blasting or polishing with a silicon-containing nylon brush, and the surface roughness measured on a length of 300 μm is Ra=0.2 μm.

In the above-mentioned preparation method of this embodiment, when the CVD coating furnace deposits various coatings, its atmosphere composition, temperature and pressure are controlled as shown in Table 1 below, and the thickness of each layer of coating is controlled by adjusting the deposition time.

Table 1: Process parameter control of cutting tool in coating furnace in embodiment 1

Adopt XRD to carry out qualitative analysis to the coating phase that present embodiment 1 makes; Use SEM and EDS to analyze the surface microstructure of surface oxide outer layer D23 and transition layer C1 221, the results are shown in Figure 2 and Figure 3 respectively; Three-line method to measure the average grain size of the outer layer D23 of the surface oxide: randomly draw three parallel straight lines (length Lμm) on the photo, and count the number n of grain boundaries crossed by the lines, then the average grain size d is L /n, the average grain size S of α-Al ₂ O ₃ in the outer layer D 23 in this example is calculated to be 0.46 μm; the bonding strength of the coating prepared in this example is measured by the scratch method.

Example 2:

A cutting tool with improved coating structure of the present invention as shown in Figure 1, its coating structure, composition, microscopic composition, etc. are the same as the cutting tool in Example 1, only the outer layer α-Al ₂ O ₃ is slightly different from Example 1. In this embodiment, the thickness d of the outer layer D is 2 μm, and the average grain size S is 0.4 μm. The preparation method of the present embodiment 2 is basically the same as that of the embodiment 1, only need to make adaptive adjustments on the process parameters.

Example 3:

A cutting tool with improved coating structure of the present invention as shown in Figure 1, comprising a substrate A1 and a coating 2 at least partially covered on the substrate A1, the coating 2 includes at least an inner layer B21, a transition layer from the inside to the outside layer C22 and outer layer D23;

in:

The inner layer B21 is mainly composed of MT-TiCN material with a thickness of 4 μm;

The outer layer D23 is mainly composed of α-Al ₂ O ₃ material with a thickness of d=3μm. The outer layer D23 is an ultra-fine-grained oxide coating. The average grain size S of α-Al ₂ O ₃ in the outer layer D is 0.49 μm;

Transition layer C22 includes transition layer C1 221 and transition layer C2 222 from outside to inside:

The transition layer C1 221 is mainly composed of titanium carbonitride TiC _x1 N _y1 O _z1 (specifically TiC _0.3 O _0.7 ), that is, x1=0.3, y1=0, z1=0.7, z1/(x1+y1+z1) =0.7; the transition layer C1 is a flaky (or granular) nanocrystalline structure, the thickness of the transition layer C1 is 0.3 μm, and the grain size of the transition layer C1 is less than 200 nm;

The transition layer C2 222 is mainly composed of titanium carbonitride TiC _x2 N _y2 O _z2 (specifically TiC _0.8 N _0.15 O _0.05 ), that is, x2=0.8, y2=0.15, z2=0.05, and x2/(x2+y2 +z2)=0.8; the transition layer C2 is a discretely distributed nano-equiaxed particle structure, the thickness of the transition layer C2 is 0.2 μm, and the grain size of the transition layer C2 is less than 200 nm.

The cutting tool of the above-mentioned present embodiment is mainly prepared by the following method:

(1) Preparation of cemented carbide matrix: first use a ball mill to wet mix 6wt% Co, 3.5wt% Ti and Ta cubic carbonitrides, and the rest of the WC powder for 20 hours, dry the mixture, and press it into a compact. The compact is sintered into a carbide tool substrate, the surface and cutting edge of which are wet blasted; the following coatings are then deposited on said tool substrate in the same coating cycle:

The operations of steps (2) to (6) in this embodiment are basically the same as those in Embodiment 1, except that the process parameters in the coating furnace can be adjusted accordingly (see Table 1).

Use SEM and EDS to analyze the surface microstructure of the surface oxide outer layer D23 of this embodiment, and the results are as shown in Figure 4; measure and calculate the average grain size S of α-Al in the outer layer D23 in this embodiment ₂ O ₃ is 0.49 μm .

Example 4:

A cutting tool with improved coating structure of the present invention, its substrate is basically the same as in Example 3, and the coating structure, composition, microscopic composition, etc. are completely the same as the cutting tool in Example 3, except that the outer layer α- Al ₂ O ₃ is slightly different from Example 3. In this embodiment, the thickness d of the outer layer D is 1.4 μm, and the average grain size S is 0.32 μm. Steps (1) to (6) of the preparation method of the cutting tool in this embodiment are basically the same as in Embodiment 3, only need to make adaptive adjustments on the process parameters; Deposit a layer of the above-mentioned Ti-containing compound marking layer; after surface treatment, remove the aforementioned marking layer on the local area of the cutting edge, rake face or flank face of the coated blade to expose the outer layer B, and complete the production.

Select 4 other comparative cutting tools:

Cutting tool one (comparative example 1) substrate is the same as that of Example 1, and the coating process of the inner layer B is the same as that of Example 1, lacking the transition layer C. In this example, the thickness d of the outer layer D is 3.5 μm, and the average crystal grain The degree S is 1.1 μm.

Cutting tool 2 (comparative example 2) has the same substrate as in Example 1, the coating process of the inner layer B is the same as in Example 1, the transition layer C has only C1 with a thickness of 1 μm, the thickness d of the outer layer D is 4.2 μm, and the average crystal grain The degree S is 1.3 μm.

Cutting tool three (comparative example 3) substrate is the same as that of Example 3, the coating process of the inner layer B is the same as that of Example 3, and the outer layer D is prepared according to the scheme provided in the CN1091683A Chinese patent document, and the thickness d of the outer layer D is 7 μm. The average grain size S was 1.7 μm.

The main coating structures of the above embodiments and comparative examples are shown in Table 2 below, wherein the surface microstructure of the outer layer D of comparative example 1 is as shown in Figure 5; the surface microstructure of the outer layer D and transition layer C1 of comparative example 2 The structure is shown in Figure 6 and Figure 7.

Table 2: Thickness comparison of main coating structures of various cutting tools

The cutting tools of Example 1 and Example 2 above and Comparative Cutting Tools 1 and 2 were subjected to the turning test shown in Table 3 below and the milling test shown in Table 4 below, respectively.

Table 3: Turning Test Patterns

Table 4: Milling test pattern

The results of the above-mentioned turning test and milling test are shown in Table 5 below.

Table 5: Comparison of test results

It can be seen from the above table 5 that: the surface of the cutting tool of the comparative examples has α and κ mixed crystal alumina, and the crystal grains are coarse or uneven in thickness, etc., while the surface of the cutting tool of the embodiment of the present invention is uniform; The grain size of layer D is under the condition that coating thickness is equivalent, and the grain size of outer layer D of the present invention is obviously finer than the oxide coating prepared by prior art; Visible, adopt technology of the present invention to prepare grain A fine oxide coating with a single-phase α-Al2O3 structure.

The grains on the surface of the cutting tool of the comparative example are abnormally thick and there is a phenomenon of clamping, and the life of the tool fluctuates greatly; while the grains on the surface of the cutting tool of the embodiment of the present invention are fine and uniform, and show good bonding strength in the scratch test. In the cutting experiment, it showed a long service life and stability.

Claims (10)

1. A cutting tool with improved coating structure, comprising a substrate A and a coating at least partially covered on the substrate A, the coating comprises an inner layer B, a transition layer C and an outer layer D from the inside to the outside; The inner layer B is mainly composed of compound materials composed of transition elements and non-metallic elements in the periodic table of elements, and the transition elements are selected from at least one of group IVB, group VB, and group VIB in the periodic table of elements. The non-metallic element is selected from at least one of carbon, nitrogen, oxygen, and boron; It is characterized in that the transition layer C includes a transition layer C1 and/or a transition layer C2 from outside to inside; The transition layer C1 is mainly composed of titanium carbonitride TiC _x1 N _y1 O _z1 , and the x1, y1, and z1 respectively represent the atomic percentages of C, N, and O in TiC _x1 N _y1 O _z1 , and satisfy 0.5≤ z1/(x1+y1+z1)≤1, y1≤x1≤z1; The transition layer C2 is mainly composed of titanium carbonitride TiC _x2 N _y2 O _z2 , and the x2, y2, and z2 respectively represent the atomic percentages of C, N, and O in TiC _x2 N _y2 O _z2 , and satisfy 0.5≤ x2/(x2+y2+z2)≤1, The outer layer D has a single-phase α-Al ₂ O ₃ structure, the thickness of the outer layer D is d=0.5 μm˜4 μm, and its average grain size S is 0.2 μm≤S≤0.5 μm. 2. The cutting tool with improved coating structure according to claim 1, characterized in that: in the transition layer C1, the x1, y1, z1 satisfy 0.5≤z1/(x1+y1+z1)≤0.8; the The transition layer C1 has a sheet or granular nanocrystalline structure, the grain size of the transition layer C1 is less than 200 nm, and the thickness of the transition layer C1 is less than 0.5 μm. 3. The cutting tool with improved coating structure according to claim 1, characterized in that: in the transition layer C2, the x2, y2, z2 satisfy 0.8≤x2/(x2+y2+z2)≤1; The transition layer C2 is a discretely distributed nano-equiaxed particle structure, the grain size of the transition layer C2 is less than 200 nm, and the thickness of the transition layer C2 is less than 0.5 μm. 4. The cutting tool with improved coating structure according to claim 3, characterized in that: said x2=1, y2=0, z2=0, said transition layer C2 is a TiC coating, said transition layer C2 The thickness is less than 0.3 μm. 5. The cutting tool with improved coating structure according to any one of claims 1 to 4, characterized in that: the compound material of the inner layer B is selected from carbides, nitrides, borides, oxides, carbon One or more of nitrides, boronitrides, and borocarbonitrides, at least one of the compound materials has a columnar or fibrous crystal structure. 6. The cutting tool with improved coating structure according to claim 5, characterized in that: said inner layer B comprises a layer of MT-TiCN with a thickness greater than 3 μm. 7. The cutting tool with improved coating structure according to any one of claims 1-4, characterized in that: the total thickness of the transition layer C is 0.1 μm-0.8 μm. 8. The cutting tool with improved coating structure according to any one of claims 1 to 4, characterized in that: a marking layer E containing a Ti compound is coated on the outer side of the outer layer D, and the marking layer E containing Ti The thickness of the Ti compound marking layer is 0.1 μm˜1 μm. 9. A preparation method of the cutting tool for improving the coating structure according to any one of claims 1 to 8, comprising the following steps: first preparing hard alloy, cermet, non-metal ceramic, PCD or CBN material Tool substrate, on which the following coatings are then deposited in the same coating cycle: (1) Deposit the above-mentioned inner layer B on the tool substrate A by conventional CVD method; (2) Depositing the above-mentioned transition layer C2 on the inner layer B using a conventional HT-CVD process; (3) Depositing the above-mentioned transition layer C1 on the transition layer C2 by conventional HT-CVD method; (4) depositing the above-mentioned outer layer D on the transition layer C1 by conventional HT-CVD method; (5) adopt sandblasting or silicon-containing nylon brush polishing to carry out surface treatment to above-mentioned hard alloy coating blade made; (6) Utilize the conventional CVD method to deposit one layer of the above-mentioned Ti-containing compound marking layer on the outer layer D; Remove the aforementioned marking layer to expose the outer layer B to complete the fabrication. 10. The preparation method according to claim 9, characterized in that: the deposition of the outer layer D refers to optimizing the shape of the transition layer C1 by using a mixed gas of CO, CO ₂ and H ₂ S on the transition layer C1. nucleation, and then after the alumina nucleation of the outer layer D, the growth of the alumina coating is optimized using H ₂ S or SF ₆ to obtain the fine-grained α-Al ₂ O ₃ structure; the outer layer The deposition process of D is controlled at a temperature range of 900°C to 1020°C.