RU2268321C1 - Method of making multi-layer coat for cutting tools - Google Patents

Abstract

FIELD: application of wear-resistant coats on cutting tools; metalworking.

SUBSTANCE: proposed method includes vacuum plasma application of multi-layer coat: lower layer contains titanium and metal, intermediate layer contains titanium nitride or carbonitride and metal and upper layer contains material of intermediate layer alloyed by chromium; used as metal is aluminum, iron, molybdenum, zirconium or silicon; application of layers is performed by means of three cathodes located horizontally in one plane; two cathodes are located opposite; third cathode is made from titanium and chromium.

EFFECT: enhanced serviceability of cutting tools; enhanced strength of adhesion with base.

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Description

The invention relates to methods for applying wear-resistant coatings to a cutting tool and can be used in metalworking.

There is a method of increasing the resistance of a cutting tool (RI), in which a wear-resistant coating (PI) of titanium nitride (TiN) or titanium carbonitride (TiCN) is applied on its surface using a vacuum-arc method (see Tabakov V.P. Performance of a cutting tool with wear-resistant coatings based on complex nitrides and titanium carbonitrides. Ulyanovsk: UlSTU, 1998. 123 p.). The reasons that impede the achievement of the following technical result when using the known method include the fact that in the known method, the coatings have relatively low hardness and level of compressive stresses and insufficient adhesion to the tool base. As a result of this, the coating undergoes more wear and tear, cracks quickly nucleate and propagate in it, leading to the destruction of the coating, which reduces the resistance of the RI with the coating.

The closest method of the same purpose to the claimed invention in terms of features is a method of increasing the resistance of RI, including applying a multilayer wear-resistant coating containing a hard alloy tool base and a three-layer wear-resistant coating applied by GT VNIITS and consisting of an upper layer of titanium nitride TiN , an intermediate layer of titanium carbonitride TiCN and the lower layer of titanium carbide TiC (see Vereshchak A.S. Performance of cutting tools with wear-resistant coatings M .: Engineering, 1993. p. 252), adopted as a prototype.

For reasons that impede the achievement of the following technical result when using the known method adopted as a prototype, the multilayer coating in the known method contains layers of titanium carbide, nitride and carbonitride having low adhesion strength to the tool base and to each other and low crack resistance . As a result, the coating poorly resists the processes of wear and tear and quickly collapses when cutting.

Recently, the increase in the cost of metal-cutting tools and the tightening of requirements for precision machined parts made the problem of increasing the resistance of radiation sources even more urgent. The main reason for the destruction of the coating is the occurrence of cracks due to deformation of the cutting wedge and adhesive-fatigue phenomena, which are the cause of the occurrence of spalling of the IP material on the contact pads. Moreover, for multilayer coatings, layer separation is observed under the influence of descending chips. One of the ways to increase the resistance and, as a consequence, the performance of RI with a coating is to apply multilayer coatings with layers with different physical and mechanical properties, which makes it possible to create barriers in the form of boundaries between the layers on the crack path. The presence in the coating of the upper layer with high residual compressive stresses, further contributes to an increase in crack resistance of the coating. To increase the adhesion strength of the coating to the tool base, it should include a lower layer with improved adhesive properties. An increase in the adhesion strength of the layers is ensured by their chemical affinity for each other.

The technical result is an increase in the health of RI.

The specified technical result during the implementation of the invention is achieved in that a titanium and metal compound is applied as a lower coating layer, titanium and metal nitride or carbonitride as an intermediate, and the same material as the upper layer, but doped with chromium, as the upper one. A feature of the proposed method lies in the fact that a titanium and metal compound is applied as the lower coating layer, titanium and metal nitride or carbonitride as an intermediate layer, and the same material as the upper layer, but alloyed with chromium, is used as the upper layer. The layout of the TiMe-TiMeN-TiMeMoN coating system (or TiMe-TiMeCN-TiMeMoCN) includes two opposing composite cathodes of titanium and metal and a composite cathode of titanium and chromium located between them. As the metal Me use aluminum, iron, molybdenum, zirconium, silicon. This coating structure allows to obtain high adhesion to the base of the lower layer, which has high adhesion to the tool base. In this case, the upper layer has high hardness and compressive stresses necessary for braking cracks. The presence between the upper and lower layers of the transition layer, including the components of the upper and lower layers, increases the bond strength of the layers in the coating. An increase in crack resistance is facilitated by the layered structure of the coating, due to which cracks are inhibited at the boundaries of the layers.

The analysis of the prior art by the applicant, including a search by patents and scientific and technical sources of information, and the identification of sources containing information about analogues of the claimed invention, allowed to establish that the applicant did not find sources characterized by features identical to all the essential features of the claimed invention. The definition from the list of identified analogues of the prototype, as the closest in the totality of the features of the analogue, allowed us to establish a set of essential distinguishing features in relation to the technical result perceived by the applicant in the claimed method set forth in the claims. Therefore, the claimed invention meets the condition of "novelty."

To verify the compliance of the claimed invention with the condition "inventive step", the applicant conducted an additional search for known solutions in order to identify signs that match the distinctive features of the claimed method of increasing the efficiency of RI, distinctive from the prototype. The search results showed that the claimed invention does not follow explicitly from the prior art for the specialist, since the influence of the transformations provided for by the essential features of the claimed invention on the achievement of the technical result is not revealed from the prior art determined by the applicant. In particular, the claimed invention does not provide for the following transformations:

- the addition of a known means by any known part, attached to it according to known rules, to achieve a technical result, in respect of which the effect of such an addition is established;

- replacement of any part of a known product with another known part to achieve a technical result, in respect of which the effect of such a replacement is established;

- the exclusion of any part of the funds with the simultaneous exclusion of the function due to its presence and the achievement of the usual result for such exclusion;

- an increase in the number of elements of the same type, actions to enhance the technical result, due to the presence in the tool of just such elements, actions;

- the implementation of a known tool or part of a known material to achieve a technical result due to the known properties of this material;

- the creation of a tool consisting of known parts, the choice of which and the relationship between them are based on known rules, recommendations, and the technical result achieved in this case is due only to the known properties of the parts of this tool and the relationships between them.

The described invention is not based on a change in the quantitative characteristic (s), the presentation of such signs in relationship, or a change in its form. This refers to the case when the fact of the influence of each of these characteristics on the technical result is known, and new values of these signs or their relationship could be obtained on the basis of known dependencies and patterns. Therefore, the claimed invention meets the condition of "inventive step".

The invention consists in the following.

During cutting, cracking processes occur in the coating, leading to its destruction. In addition, due to insufficient adhesion to the tool base and layers inside the multilayer coating, the latter can be destroyed as a result of adhesion-fatigue phenomena on the contact pads. Under these conditions, the coating should have a layered structure with areas of different hardness to inhibit cracks. The bottom layer of the coating must have high adhesion to the tool material. The top layer must have high hardness and residual compressive stresses to increase wear and crack resistance. In this case, the layers of the multilayer coating should have high bond strength with each other, which is ensured by the introduction of an intermediate layer containing the components of the upper and lower layers.

Coated plates obtained with deviations from the indicated production technology showed lower results.

For experimental verification of the claimed method, a prototype coating was applied with a layer ratio corresponding to the optimal value specified in the known method, as well as a three-layer coating according to the proposed method. The coatings were applied to carbide plates in the vacuum chamber of the Bulat-6T installation, equipped with three vacuum-arc evaporators located horizontally in the same plane.

The proposed coating is as follows.

MK8 carbide inserts (4.7 × 12 × 12 mm in size) are washed in an ultrasonic bath, wiped with acetone, alcohol and mounted on a rotary device in the vacuum chamber of the Bulat-6 installation equipped with three evaporators located horizontally in the same plane. Two opposing composite cathodes of titanium and metal and a composite cathode of titanium and chromium located between them are used. The chamber is pumped out to a pressure of 6.65 · 10 ^-3 Pa, the rotator is turned on, a negative voltage of 1.1 kV is applied to it, one evaporator is turned on and at an arc current of 100 A, the plates are cleaned and heated to a temperature of 560-580 ° C . The focusing coil current is 0.4 A. Then, at a negative voltage of 160 V and a coil current of 0.3 A, two Ti-Me evaporators are turned on and a 2.0 μm thick TiMe coating is deposited. The second layer of TiMeN (or TiMeCN) with a thickness of 2 μm is applied at a negative voltage of 160 V, a current of coils of 0.3 A, turned on Ti-Me evaporators and a supply of reaction gas - nitrogen (or a mixture of nitrogen and acetylene). A third layer of TiMeCrN (or TiMeCrCN) with a thickness of 2 μm is applied at a negative voltage of 160 V, a coil current of 0.3 A, a supply of nitrogen (or a mixture of nitrogen and acetylene) and the inclusion of all three evaporators. Then shut off the evaporators, the supply of reaction gas, voltage and rotation of the device. After 15-20 minutes, the chamber is opened and the coated tool is removed.

Durability tests were carried out on a model 16K20 lathe with cutters with replaceable polyhedral MK8 carbide inserts when machining workpieces from ZOKhGSA structural steel. Tested carbide inserts grade MK8, processed by the known and proposed methods. The wear criterion was a chamfer of wear along the back surface with a width of 0.4 mm.

As can be seen from the data in table 1, the resistance of the plates processed by the proposed method is higher than the wear resistance of the plates processed by the prototype method in 2.1-2.6 times.

Thus, the above information indicates that when using the claimed method of obtaining a wear-resistant coating for RI the following set of conditions:

- a method for producing a multilayer coating for RI, embodying the claimed method in its implementation, is intended for use in industry, namely for applying wear-resistant coatings to RI, and can be used in metal processing;

- for the claimed method for producing a multilayer coating for RI in the form described in the independent claim, the possibility of its implementation using known means and methods prior to the priority date is confirmed;

- a method of producing a multilayer coating to obtain a wear-resistant coating for RI, embodying the claimed method, when implemented, is able to achieve the achievement of the technical result perceived by the applicant.

Table 1
Coated RI Test Results No pp Coating material The thickness of the coating layers, microns Resistance, min Note 1 layer 2 layer 3 layer one 2 3 four 5 6 7 The processed material - 30KhGSA, V = 180 m / min, S = 0.15 mm / min, t = 1.0 mm one TiN 6 - - 45 Analogue 2 TiC-TiCN-TiN 2 2 2 131 Prototype 3 TiAl-TiAlN-TiAlCrN 2 2 2 293 - four TiAl-TiAlCN-TiAlCrCN 2 2 2 329 - 5 TiFe-TiFeN-TiFeCrN 2 2 2 279 - 6 TiFe-TiFeCN-TiFeCrCN 2 2 2 303 - 7 TiMo-TiMoN-TiMoCrN 2 2 2 276 - 8 TiMo-TiMoCN-TiMoCrCN 2 2 2 297 - 9 TiZr-TiZrN-TiZrCrN 2 2 2 284 - 10 TiZr-TiZrCN-TiZrCrCN 2 2 2 321 - eleven TiSi-TiSiN-TiSiCrN 2 2 2 309 - 12 TiSi-TiSiCN-TiSiCrCN 2 2 2 338 -

1. Tool material - MK8.

Therefore, the claimed invention meets the condition of "industrial applicability".

Claims (1)

A method of obtaining a multilayer coating for a cutting tool, including vacuum-plasma deposition of a multilayer coating, characterized in that the lower layer is applied from a compound of titanium and metal, the intermediate layer is made of titanium nitride or carbonitride and metal, and the upper layer is made of an intermediate layer material alloyed with chromium, in this case, aluminum, or iron, or molybdenum, or zirconium, or silicon is used as the metal, and the coating layers are applied by three cathodes arranged horizontally in one plane and, two of which are located opposite and are made of composite of titanium and the metal used, and the third is made of composite of titanium and chromium.