RU2490358C1 - Method for obtaining multi-layered coating for cutting tool - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: vacuum plasma application of multi-layered coating is performed. First, lower layer of nitride of titanium, zirconium and niobium is applied at the following component ratio, wt %: titanium 80.0-88.0, zirconium 6.0-10.0, niobium 6.0-10.0. After that, intermediate layer of carbonitride of titanium, zirconium and niobium compound is applied at the following component ratio, wt %: titanium 80.0-88.0, zirconium 6.0-10.0, niobium 6.0-10.0. After that, upper layer of nitride of titanium and zirconium compound is applied at the following component ratio, wt %: titanium 85.0-91.0, zirconium 9.0-15.0. Application of coating layers is performed with three cathodes horizontally located in one plane; the first and the second of the above cathodes are made from titanium and zirconium and located opposite to each other, and the third cathode is made from titanium and niobium and located between them. Lower and intermediate layers are applied using all the three cathodes, and upper layer is applied using the first and the second cathodes.

EFFECT: improving operability of a cutting tool.

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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-plasma 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 technical result indicated below when using the known method include the fact that in the known method, the applied coating does not provide the same high efficiency when a cutting tool operates with this coating under intermittent cutting conditions, in particular during milling, as during continuous cutting .

The closest method of the same purpose to the claimed invention in terms of features is the method of applying a multilayer coating, disclosed in the description of the patent for invention RU 2269604 C1, adopted as a prototype.

For reasons that impede the achievement of the technical result indicated below when using a known cutting tool with a coating adopted as a prototype, the multilayer coating in the known method has insufficient hardness, and therefore, crack resistance and low compressive residual stresses. As a result, the coating poorly resists the processes of wear and tear and quickly collapses when cutting.

One of the ways to increase the resistance and, as a consequence, the health of RI with a coating is to apply multilayer coatings with layers with different physical and mechanical properties. The presence in the coating of the upper layer, which has high hardness and contact characteristics, helps to reduce the wear rate of RS with a multilayer coating. To increase the adhesion strength of the coating to the tool base, it should include a lower layer with high adhesive properties. In addition, an increase in the hardness of the lower coating layer also contributes to an additional decrease in the wear rate of RS with a multilayer coating. The intermediate layer should perform the following functions. First, to provide increased adhesion of the layers due to its formation from the elements of the upper and lower layers. Secondly, to have high hardness and compressive residual stresses to reduce the intensity of wear and cracking in the coating during interrupted cutting. Thirdly, to increase the crack resistance of the entire coating due to the appearance of additional boundaries between the layers.

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

The specified technical result in the implementation of the invention is achieved by applying a lower layer of nitride compounds of titanium, zirconium and niobium at their ratio, wt.%: Titanium 80.0-88.0, zirconium 6.0-10.0, niobium 6, 0-10.0; intermediate - from a carbonitride of a compound of titanium, zirconium and niobium at their ratio, wt.%: titanium 80.0-88.0, zirconium 6.0-10.0, niobium 6.0-10.0; the top one is made of titanium and zirconium compounds nitride at their ratio, wt.%: titanium 85.0-91.0, zirconium 9.0-15.0, and coating layers are applied by three cathodes lying horizontally in the same plane, the first and second of which they are made composite of titanium and zirconium and are located opposite to each other, and the third is made composite of titanium and niobium and placed between them, the lower and intermediate layers being applied using all three cathodes, and the upper layer using the first and second cathodes.

This structure of the applied coating allows to obtain high residual stresses and hardness due to the presence of an intermediate layer in the coating. In this case, the lower and intermediate layers have high hardness and crack resistance due to additional alloying of the material of the coating layers and the presence in their structure of microlayers obtained by coating according to the proposed cathode arrangement.

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 adhesive-fatigue phenomena on the contact pads. Under these conditions, the coating should have a layered structure to inhibit cracks and high compressive stresses. The coating layers must also have high hardness to increase wear and crack resistance. Moreover, the layers of the multilayer coating should have high bond strength between each other, which is ensured by their high affinity for each other due to the presence of common elements.

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 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 cathodes located horizontally in the same plane. The first and second composite cathodes of titanium and zirconium located opposite each other are used, and the third composite cathode of titanium and niobium located between them. 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 cathode 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, a coil current of 0.3 A and a supply of reaction nitrogen gas, all three cathodes are turned on and a 2.0 μm thick TiZrNbN coating layer is deposited. An intermediate coating layer of TiZrNbCN with a thickness of 2.0 μm is applied at a negative voltage of 160 V, a current of coils of 0.3 A and three cathodes turned on when a reaction gas consisting of a mixture of nitrogen and acetylene (60% nitrogen and 40% acetylene (wt.)) Is supplied . The upper layer of a TiZrN coating with a thickness of 2.0 μm is applied at a negative voltage of 160 V, a current of coils of 0.3 A, the first cathodes (made of titanium and zirconium) and the second (made of titanium and zirconium) and a nitrogen reaction gas supply. 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.

The microhardness of the coatings was determined on a PMT-3 microhardness meter under a load of 100 g. Residual stresses were determined on a DRON-3M X-ray diffractometer using filtered Cu _Kα radiation.

Durable tests of the cutting tool were carried out with symmetrical face milling of 5XNM steel blanks on a 6P12 machine. Tested carbide inserts grade MK8, processed by the known and proposed methods. The cutting conditions were as follows: cutting speed V = 247 m / min, feed S = 0.4 mm / tooth, cutting depth t = 1.5 mm, milling width B = 20 mm. For the wear criterion, the value of the chamfer of wear on the rear surface h ₃ = 0.4 mm was taken.

Table 1 shows the test results of RI with the obtained coatings.

As can be seen from the data in table 1, the resistance of the plates with the coatings deposited by the proposed method is higher than the resistance of the plates with the coating deposited by the prototype method by 1.12-1.41 times.

Claims (1)

A method of obtaining a multilayer coating for a cutting tool, including vacuum-plasma deposition of a multilayer coating, characterized in that a lower layer of nitride of a compound of titanium, zirconium and niobium is applied at their ratio, wt.%: Titanium 80.0-88.0, zirconium 6 , 0-10.0, niobium 6.0-10.0, intermediate - from carbonitride compounds of titanium, zirconium and niobium at their ratio, wt.%: Titanium 80.0-88.0, zirconium 6.0-10, 0, niobium 6.0-10.0, and the top - from nitride compounds of titanium and zirconium with their ratio, wt.%: Titanium 85.0-91.0, zirconium 9.0-15.0, and applying It is coated with three cathodes arranged horizontally in the same plane, the first and second of which are made of titanium and zirconium and arranged opposite to each other, and the third is made of titanium and niobium and placed between them, the lower and intermediate layers being applied using all three cathodes, and the upper layer using the first and second cathodes.