RU2693225C1 - Drill with mechanical fastening of cutting plates and its housing with wear-resistant coating - Google Patents

Abstract

FIELD: processing of materials.

SUBSTANCE: invention relates to machining of materials and can be used in designs of drills with mechanical fastening of cutting plates. Drill housing with wear-resistant coating formed by physical vapor deposition on its surface comprises working part with circular outer surface arranged around rotational axis. On the working part on the side of free end there are sockets for arrangement and attachment of cutting plates. Along the working part there are made drill flutes. Wear-resistant coating containing at least one layer with residual compression stresses is applied on the surface of at least the working part of the housing. Wear-resistant coating has non-uniform thickness along the working part length and contains at least a layer of amorphous diamond-like carbon material as a layer having residual compressing stresses.

EFFECT: increased serviceability and durability of drills.

10 cl, 6 dwg

Description

The field of technology.

The present invention relates to metal-cutting tools, in particular to drills with mechanical fastening of the cutting plates and their bodies.

The level of technology.

For high-performance drilling of holes in products made, including from hard-to-machine materials, drills with mechanical fastening of interchangeable cutting inserts are used.

The main structural element of these drills is their case, which has an axis of rotation, around which the working part is located with sockets on the end for placing and fixing in them, for example, with the help of screws of interchangeable cutting plates.

For removal of chips from the cutting edges of the cutting plates of the body of the drill also contain a sample made along the working part of the drill and called, as a rule, the chip discharge grooves. They alternate with cylindrical sections of the working part of the drill body. When this surface of these cylindrical sections are located at a maximum distance from the axis of rotation of the drill. Drill bodies may also have holes for coolant supply to the cutting area.

When drilling holes in products from difficult-to-cut materials, the body of the drill suffers from significant loads, accompanied by torsional vibrations and a complex stress-strain state of its working part. Maximum tangential stresses appear on the surfaces of the cylindrical sections of the working part of the body. While moving these areas relative to the walls of the hole along the working part of the body of the drill is not evenly due to increasing in the direction of the end of the working part of the angle of rotation relative to the axis of rotation when it is twisted.

Usually part of the cutting plates attached to the end of the drill, are located asymmetrically relative to its axis of rotation. This additionally causes an increase in non-uniformly distributed loads acting on the working part of the tool, both along its length and in the radial direction relative to its axis of rotation.

In the process, the surface of the working part of the drill body is also exposed to an aggressive environment, operating at high temperatures. This is due, for example, the impact of chips, having the highest temperature in the cutting zone, located at the end of the working part of the body of the drill.

As a result of the impact of chips on the surface of the chip discharge grooves having a high coefficient of sliding friction, their uneven wear may occur along the working section, which has the greatest value in the direction of its end face.

This may be accompanied by sticking of the material being processed on the surface of the chip grooves, which significantly complicates the removal of chips from the cutting zone, increases the cutting force and energy consumption for cutting materials, and can also cause chip packaging and destruction of the cutting tool body.

The high coefficient of friction of chip discharging surfaces can also contribute to the uneven wear of these surfaces, leading to uneven loading of the working part of the drills and, consequently, to the removal of drills from the axis of the hole.

When drilling due to uneven loading of the working part of the body of the drill, forced vibrations may also occur, including vibrations, including torsional vibrations, negatively affecting the hole accuracy, durability of the cutting plates and the service life of the body and drill as a whole. At the same time, the surface of the sections of the chip-removing grooves and the cylindrical surfaces of the working part of the body, which are located closer to the working end face of the drill body, are subjected to the greatest thermomechanical load.

In connection with the specified features of using drills with mechanical fastening of interchangeable cutting plates, the working part of their bodies experiences asymmetric thermomechanical loads that are not evenly distributed along its length. Moreover, these loads increase in the direction from the drill shank to the end of their working part.

The above negative factors acting on the working part of the drill body significantly reduce the efficiency and resource of not only the case, but also the drill as a whole, and also lead to a significant investment of time and energy when cutting materials.

Taking into account the above features of using the above drills, their bodies should have high strength and rigidity, including torsional and flexural rigidity, and the surface of their working part should have increased hardness, corrosion resistance and low coefficient of sliding friction relative to the material being processed.

To increase the strength and rigidity of the working part of drill housings with mechanical fastening of interchangeable cutting plates, high-strength materials and various shapes and sizes are used, both the working part and the shapes and dimensions of the chip removal grooves and the geometry of the cutting part. In this case, it is very difficult to take into account the asymmetrical loading of the working part of the bodies of these drills using conventional means, since their reserves are largely exhausted.

For example, a drilling tool is known (RF patent No. 2568540), which comprises a main body that is rotatable around a longitudinal axis. Along the working part of the body there are chip-removing grooves alternating with sections of a cylindrical surface, and interchangeable cutting plates are installed at the end of the body in the sockets. The design of this tool does not take into account the above-mentioned features of the operation of drills, which will significantly affect its durability and durability.

To improve the performance properties of the cutting tool cases, wear-resistant protective coatings are used, including those with residual compressive stresses.

Known, for example, (RF patent for useful model No. 153821) cutter body with a protective coating having a low coefficient of friction on aluminum alloys. At the same time, the protective wear-resistant coating is made of three layers by vacuum-arc spraying and contains an anticorrosive layer based on chromium deposited on the cutter body, a transition layer and a layer of amorphous diamond-like carbon material.

The use of a diamond-like carbon material or diamond-like carbon with a tungsten alloying material as a low friction layer can significantly reduce the interaction and sticking of chips to the surface of the body.

However, the above-mentioned construction of tool housings with mechanical fastening of interchangeable cutting plates do not have special protective wear-resistant coatings applied to the working part of their housings, taking into account their asymmetric loading, which significantly reduces their operational properties.

The present invention is the creation of the body of the drill with mechanical fastening of the cutting plates of increased efficiency and durability due to the use of properties of wear-resistant coating to compensate for the negative effect of asymmetric loading of its working part.

The present invention is also the creation of a drill with mechanical fastening of cutting plates of increased efficiency and durability.

To do this, in the working part of the drill body, you must first, that is, before its work, create internal mechanical stresses taking into account the asymmetric thermomechanical effect that occurs when drilling holes, and also selectively increase the wear resistance of individual parts of the drill case.

At the same time, in order to achieve a high technical result in a new constructive solution, the properties of the material should be used as a single structural element with its shape and dimensions, allowing targeted high residual internal stresses, low coefficient of sliding friction, high hardness and thermal conductivity.

DISCLOSURE OF INVENTION

This technical result is achieved by a combination of features that are given in the respective claims.

The drill body with a wear-resistant coating formed by physical vapor deposition on its surface contains a working part located around the axis of rotation with a circular outer surface on which slots are made for accommodating and attaching the cutting plates on the side of the free end.

Along the working part of the body, chip-removing grooves are made, and a wear-resistant coating is applied to the surface of at least the working part of the body, containing at least one layer having residual compressive stresses.

In accordance with the invention, the wear-resistant coating has an uneven thickness along the length of the working part of the drill and contains as a layer having residual compressive stresses at least a layer of amorphous diamond-like carbon material.

In accordance with one preferred embodiment of the drill body, the thickness of the wear-resistant coating decreases along the length of the working part in the direction from its working end.

In accordance with another preferred embodiment of the housing, the thickness of the wear-resistant coating on the circular outer surface of the working part furthest from the axis of rotation of the housing is greater than on the surfaces of the chip discharging grooves.

In accordance with another preferred embodiment of the housing, the thickness of the wear-resistant coating on the surfaces of the chip dispensing grooves in the radial direction from the axis of rotation of the housing to the periphery of its working part has a variable value.

In accordance with another preferred embodiment of the housing, the thickness of the wear-resistant coating is in the range of 0.5 to 5 μm, and the residual compressive stresses in it are in the range of 4-10 hPa.

In accordance with another preferred embodiment of the housing, the wear-resistant coating is made multi-layered, and the layer of amorphous diamond-like carbon material is made upper.

In accordance with another preferred embodiment of the housing, the protective wear resistant coating further comprises a chromium-based anti-corrosion layer applied to the surface of the housing.

In accordance with another preferred embodiment of the casing, an amorphous diamond-like carbon with a tungsten dopant in an amount of 0.5-2.3% is used as an amorphous diamond-like carbon material.

According to the invention also proposed drill with mechanical fastening of the cutting plates. It includes a housing, on the working part of which cutting plates are located in the sockets, and along the working part there are made chip-removing grooves. In this case, the drill has a body made with a wear-resistant coating according to one of the designs indicated above.

In accordance with one preferred embodiment of the drill, its cutting plates are made with a wear-resistant coating.

For a better understanding, but only as an example, the invention will now be described with reference to the attached drawings, which shows the design of the drill body with the mechanical fastening of interchangeable cutting inserts and the drill itself.

FIG. 1 shows in perspective a drill body with a wear-resistant coating;

in fig. 2 shows a section along the line A-A of the working part of the drill body shown in FIG. one;

in fig. 3a, b structurally depict fragments of a wear-resistant coating deposited on the working part of the drill body, respectively in sections I-I and II-II of FIG. 2;

in fig. 4 shows a section along the line B-B of the working part of the drill body shown in FIG. one;

in fig. 5a and b structurally depict fragments of a wear-resistant coating deposited on the working part of the drill body, respectively in sections III-III and IV-IV of FIG. four;

in fig. 6 shows a drill assembly with cutting inserts in perspective.

Detailed description of the invention.

The housing 10 of the drill with a wear-resistant coating formed by the method of physical vapor deposition on its surface contains a working part 14 located around the axis of rotation 12 with a circular outer surface 16.

On the working part 14, on the side of its free end 18, slots 20 are provided for accommodating and securing the cutting plates 20a.

Chip grooves 22 are formed along the working part 14. In FIG. 1, as an example, chip discharge grooves are shown that are located along a helical surface along the working section 14. Holes 26 can also be made in the case of the drill bit for supplying coolant to the cutting plates 20a.

On the surface of at least the working part 14 of the housing 10, a wear-resistant coating 24 is applied, comprising at least one layer having residual compressive stresses. In this case, wear-resistant coating can also be multi-layered.

In accordance with the invention, the wear-resistant coating 24 has an uneven thickness along the length of the working portion 14 and contains as a layer having residual compressive stresses at least a layer of amorphous diamond-like carbon material having the largest internal residual compressive stresses compared to other materials , and also low coefficient of sliding friction, high hardness and thermal conductivity. In this case, the wear-resistant coating may additionally have layers having residual compressive mechanical stresses and containing, for example, phases with one of the following elements C, Ti, Nb, Hf.

In accordance with one of the preferred versions of the housing 10, the thickness of the wear-resistant coating 24 decreases along the length of its working part 14 in the direction from its working end 18.

Thus, the proposed design of the drill body has a new structural element in the form of a wear-resistant coating having a non-uniform thickness and containing at least a layer of non-uniform thickness of amorphous diamond-like carbon material, taking into account the asymmetry of the thermomechanical loading of the drill body.

In particular, since the coating 24 according to the most preferred embodiment of the housing 10 has an uneven thickness along the length of its working part 14, and its thickness decreases along the working part 14 in the direction from its working end 18, an address pre-stressed state of the drill body to its work.

The most loaded part of the drill body, located closer to its working end, has a large thickness of wear-resistant coating, which allows to improve the mechanical characteristics of the body, firstly, by creating a preliminary mechanical stress of the working part, differentiated along its length, taking into account the asymmetric thermomechanical effect arising from the work of the drill. At the same time, internal stresses are equalized, both in the wear-resistant coating and in the working part of the body.

Secondly, the large thickness of the wear-resistant coating located on the surfaces closer to the working end of the body also makes it possible to compensate for the greater wear of the surfaces of the working part, due to the effect of temperature and chips. Thus, a drill body with a pre-stressed working part of increased rigidity and wear resistance, taking into account the asymmetry of its thermomechanical loading, was obtained.

To demonstrate the design features of the drill body, consider FIG. 1-5. FIG. 2 and 4 show sections along the lines A-A and B-B respectively of the working part 14 of the body of the drill 10 shown in FIG. 1. At the same time, the section along A-A is located closer to the free end 18 of the body 10, and the section along the line B-B is located further away from the said end.

FIG. 3a, b and 5a, b fragments of a wear-resistant coating deposited on the working part of the drill body, are shown structurally, respectively, in sections I-I, II-II of FIG. 2 and III-III, IV-IV of FIG. 4. It can be seen that the thickness h1 of the wear-resistant coating 24 on the circular outer surface 16, in section I-I is greater than the thickness h3 of the coating in section III-III, located at a greater distance from the working end of the body.

The thickness of the wear-resistant coating 24 on the surfaces of the chip-discharging grooves 22 h2 in section II-II is also greater than the thickness h4 of the wear-resistant coating in section IV-IV located at a greater distance from the working end of the body.

In accordance with the preferred embodiment of the housing 10, the thickness of the wear-resistant coating on the circular outer surface 16 of the working part 14 furthest from the axis of rotation 12 of the housing 10 is larger than on the surfaces of the chip dispensing grooves 22, i.e. h1> h2 and h3> h4 (Fig. 3a, b and 5a, b).

Thus, the large thickness of the wear-resistant coating on the circular outer surface 16 of the working part 14, which is furthest from the axis of rotation 12 of the housing 10, corresponds to the maximum tangential stresses that occur in the working part of the body when it is twisted. At the same time, on the surfaces of chip discharging grooves 22 located in the radial direction closer to the axis of rotation 12 of the housing, the thickness of the wear-resistant coating is less than on the circular outer surface 16, which corresponds to lower values of tangential stresses on said surfaces that occur when the working part of the drill 30 is twisted.

This allows you to further align the internal stresses, as in the wear-resistant coating, and in the working part of the housing in the radial direction relative to the axis of rotation 12 of the housing 10.

In accordance with another preferred embodiment of the housing, the thickness of the wear-resistant coating 24 on the surfaces of the chip removal grooves 22 in the radial direction from the axis of rotation 12 of the housing 10 to the periphery of its working part 14 has a variable value.

This is due to the fact that the tangential stresses arising during the twisting of the working part 14, both in the working part itself and in the wear-resistant coating on the surface of the chip discharge grooves, have a variable value that depends on the distance from the axis of rotation 12 and the angle of inclination of these surfaces relative to the radius the circumference of the circular outer surface 16. The specified structural element allows you to even out the internal stresses in the wear-resistant coating on the surfaces of the chip discharge grooves that allow wish to set up to reduce the wear.

In accordance with another preferred embodiment of the housing, the wear-resistant coating 24 is multi-layered, and the layer of amorphous diamond-like carbon material is made upper. This allows you to further increase the value of the achieved technical result due to the use of low coefficient of sliding friction and high thermal conductivity of the top layer of the coating.

In accordance with another preferred embodiment of the housing, the protective wear-resistant coating 24 further comprises a chromium-based anti-corrosion layer applied to the surface of the housing 10. This layer can be applied to the entire surface of the housing, including its shank, and can be an intermediate layer.

To obtain the greatest efficiency of the present technical solution in accordance with another preferred embodiment of the body 10, the thickness of the wear-resistant coating is within 0.5-5 μm, and the residual compressive stresses in it are within 4-10 hPa.

The limits of microhardness of wear-resistant coating and residual compressive stresses in it are due to the need to ensure on one side the mechanical strength of the wear-resistant coating when processing difficult-to-work materials, including titanium and its alloys, and on the other hand the need to obtain sufficient compressive forces arising in the coating with regard to residual mechanical compression stresses.

In this case, the lower limit of the thickness of the wear-resistant coating is due to the minimum thickness of the coating, which ensures its wear resistance, which will largely depend on the maximum internal mechanical stresses arising during the operation of the drill.

The upper limit of the thickness of the wear-resistant coating is due to the fact that with a further increase in the thickness in it, the total efforts due to internal residual stresses significantly increase, which adversely affects its durability.

Thus, at high processing conditions, the values of these quantities below the lower limits on the one hand can lead to premature destruction of the wear-resistant coating due to its low mechanical strength, and on the other hand, sufficient values of the total compressive forces in the wear-resistant coating required for compensation will not be achieved. asymmetric loading of the working part of the drill body. At the same time, the values of the thickness of the wear-resistant coating above the specified upper limits can also contribute to the destruction of the wear-resistant coating due to significant total efforts in it.

In order to increase the durability of the protective wear-resistant coating of the housing 10, amorphous diamond-like carbon with a dopant of tungsten in an amount of 0.5 - 2.3% can be used as an amorphous diamond-like carbon material. This allows you to further improve the heat resistance of the wear-resistant coating, and thereby increase the planned technical result.

In accordance with the invention, a drill 30 with mechanical fastening of the cutting plates 20a is proposed. It comprises a housing 10, on the working part 14 of which cutting plates 20a are located in the sockets 20, and along the working part 14 there are made chip removal grooves 22.

According to the invention, the housing 10 of the drill 30 is made with a wear-resistant coating in one of the above versions.

In accordance with one preferred embodiment of the drill 30, the cutting plates 20a are made with a wear-resistant coating. The drill 30 may also include a removable end portion 32.

At the same time, the increase in the performance and durability of the drill is due to the special design of its body, described in detail above.

Examples of the implementation of the invention.

An uneven thickness of wear-resistant coatings on the surfaces of the working parts of drill bodies can be obtained, for example, as follows.

The application of wear-resistant coatings was carried out on vacuum arc spraying installations using the PVD method. At the same time, in order to obtain the most preferable version of the drill bodies, they were arranged in the cassettes with the working part upwards. In the process of applying a wear-resistant coating, the bodies performed a planetary motion in the volume of the vacuum chamber, rotating about its axis.

To obtain an uneven coating thickness on the surface of the drill housings along the length of their working part, carbon plasma sources in the installation were positioned horizontally opposite the working parts of the drills perpendicular to their axis. For example, cylindrical targets can be used as sources of carbon plasma. Moreover, to obtain the most preferred execution of the proposed constructive solution, the axis of carbon plasma sources coincided with the working ends of the drill bodies.

As a consequence, the wear-resistant coating had an uneven thickness along the length of the working part. Moreover, the thickness of the coating had the greatest value at the end of the working part and decreased in the direction from it to the body shank.

At the same time, by changing the angle of carbon plasma sources and / or the bodies themselves, as well as changing the diameter of carbon plasma sources and / or their distance to the working parts of the bodies, a wear-resistant coating can be obtained with an appropriate gradient of its thickness, both in the radial direction and along the working surface. parts of drill housings This will allow to obtain drills with specified technical characteristics depending on the material being processed and processing modes, which will significantly increase the efficiency and durability of drills with mechanical fastening of the cutting plates.

As a concrete example, a wear-resistant coating with a layer of amorphous diamond-like carbon material was applied to the working part of the drill bodies with their working diameter of 23.4 mm and the working part length of 100 mm. The thickness of the wear-resistant coating along the length of the working part was in the range of 0.6 to 2.6 microns.

When used under production conditions, drills with the specified housings for drilling holes 50 mm deep in cast billets made of steel 20GL had 1.5 times greater durability and service life compared to drill housings of conventional design.

Although the present invention has been described with a certain degree of detail, it should be understood that its various changes and modifications can be made without departing from the essence and scope of the invention set forth in the claims below.

Claims (10)

1. Drill body with wear-resistant coating formed by physical vapor deposition on its surface, containing a working part located around an axis of rotation with a circular outer surface, on which sockets for placing and attaching cutting plates are made on the side of the free end, and Chip discharging grooves are made, while a wear-resistant coating is deposited on the surface of at least the working part of the body, containing at least one layer having residual compressive e, characterized in that the wear-resistant coating has an uneven thickness along the length of the working part, while at least a layer of amorphous diamond-like carbon material is used as a layer having residual compressive stresses. 2. A housing according to Claim. 1, characterized in that the thickness of the wear-resistant coating decreases along the length of the working part in the direction from its working end. 3. A housing according to Claim. 1, characterized in that the thickness of the wear-resistant coating on the circular outer surface of the working part furthest from the axis of rotation of the housing is greater than on the surfaces of the chip discharging grooves. 4. A housing according to Claim. 1, characterized in that the thickness of the wear-resistant coating on the surfaces of the chip discharge grooves in the radial direction from the axis of rotation of the housing to the periphery of its working part has a variable value. 5. A housing according to Claim. 1, characterized in that the thickness of the wear-resistant coating is in the range of 0.5 to 5 microns, and the residual compressive stresses in it are in the range of 4-10 hPa. 6. A housing according to Claim. 1, characterized in that as an amorphous diamond-like carbon material an amorphous diamond-like carbon is used with a dopant of tungsten in an amount of 0.5 - 2.3%. 7. Case in one of the paragraphs. 1-6, characterized in that the wear-resistant coating is made of a multilayer, and the layer of amorphous diamond-like carbon material is made the top. 8. A housing according to claim. 7, characterized in that the protective wear-resistant coating further comprises a chromium-based anti-corrosion layer applied to the surface of the housing. 9. A drill with mechanical fastening of the cutting plates, comprising a housing, on the working part of which cutting plates are located in the sockets, and chip-removing grooves are made along the working part, characterized in that the housing is made according to one of paragraphs. 1-8. 10. The drill according to claim 9, characterized in that the cutting plates are made with a wear-resistant coating.

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