RU2297470C1 - Cutting tool multi-layer coating application method - Google Patents

Abstract

FIELD: processes for applying wear-resistant coatings onto cutting tools by vacuum-plasma method, possibly at metal working industry branches.

SUBSTANCE: method comprises steps of applying layers of multi-layer coating with use of three cathodes horizontally arranged in the same plane; placing two cathodes of titanium one opposite to other and placing composite electrode of titanium and molybdenum between them; applying lower layer of titanium nitride at temperature 620°C ± 10°C; applying upper layer of titanium nitride and molybdenum at temperature 550°C ± 10°C.

EFFECT: improved working capacity of cutting tool, enhanced quality of working by such tool.

1 ex, 1 tbl

Description

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

A known method of obtaining a coating for a cutting tool (RI), in which a vacuum-arc method is applied to a coating of titanium nitride (TiN) or titanium carbonitride (TiCN) (see Tabakov V.P. Performance of a cutting tool with wear-resistant coatings based on complex nitrides and titanium carbonitrides. Ulyanovsk: UlSTU, 1998. 122 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, coatings having good adhesion to the tool material have relatively low hardness and level of compressive stresses, or have high microhardness, but insufficient adhesion to the tool basis. As a result of this, the coating easily undergoes abrasive wear, and cracks are rapidly generated 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 according to a combination of features is a method for producing a multilayer coating for a cutting tool, including the chemical deposition of a multilayer coating consisting of a lower layer of titanium nitride TiN and an upper layer of titanium carbonitride TiCN (see Smirnov M.Yu. end mills by improving the design of wear-resistant coatings. Diss ... candidate of technical sciences., - Ulyanovsk. - 2000. - 232 p.), adopted as a prototype.

For reasons that impede the achievement of the technical result indicated below when using the known method adopted as a prototype, the multilayer coating in the known method contains layers of titanium nitride and carbonitride having low adhesion strength to the tool base and to each other and low wear and 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 stricter requirements for the accuracy of 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 performance of coated RIs is by applying multilayer coatings, which allow distributing functions between the layers. To increase the adhesion strength of the coating to the instrumental base, it should include layers with enhanced adhesive properties. To increase the adhesion strength of the coating and the tool base, layer deposition at different condensation temperatures can be used. It is possible to increase crack resistance and wear resistance by applying layers with high residual compressive stresses and high microhardness.

The technical result is an increase in the health of the Republic of Ingushetia and the quality of processing.

The specified technical result in the implementation of the invention is achieved by the fact that in the known method on the working surfaces of the RI by a vacuum-arc method, a multilayer coating is applied.

A feature of the proposed method lies in the fact that the deposition of coating layers is carried out horizontally arranged by three cathodes, using two oppositely arranged cathodes made of titanium and a composite cathode made of titanium and molybdenum between them, while the lower coating layer is applied from titanium nitride at a temperature 620 ± 10 ° С, and the upper one is made of titanium nitride and myolybdenum at a temperature of 550 ± 10 ° С. The high condensation temperature of the lower layer allows to increase the adhesion strength of the coating to the tool base. At the same time, the top layer has high hardness, residual compressive stresses and wear resistance. The layout of the TiN-TiMoN coating system includes two oppositely located titanium cathodes (VT1-0 alloy) and one composite cathode having a titanium housing and a molybdenum insert.

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 instrumental base, 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 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 compressive stresses to increase wear and crack resistance.

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 following is a specific example of the proposed method.

An example of a coating of TiN-TiMoN with a thickness of 6 μm.

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 titanium evaporators are used, one is a composite of titanium and molybdenum. The chamber is pumped out to a pressure of 6.65 · 10 ^-3 Pa, the rotary device 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 was 0.4 A. Then the negative voltage was increased to 220 V, two evaporators made of titanium were turned on, reaction gas — nitrogen was supplied to the chamber, and a coating with a thickness of 2.0 μm (TiN layer) was deposited for 12 minutes. A second layer of TiMoN with a thickness of 4 μm is applied at a negative voltage of 140 V, a coil current of 0.3 A and all evaporators turned on for 24 minutes. 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 1K62 lathe with cutters with replaceable polyhedral MK8 carbide inserts when machining workpieces made of 5XНМ structural steel. Tested carbide inserts grade MK8, processed according to 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 by 1.9 times.

Table 1
Coated RI Test Results No pp Coating material The thickness of the coating layers, microns Resistance, min Note 1 layer 2 layer one 2 3 four 6 7 The processed material - 5XNM, V = 200 m / min, S = 0.15 mm / min, t = 1.5 mm one TiN 6 - 45 Analogue 2 TiN-TiCN 2 four 131 Prototype 3 TiN-TiMoN 2 four 253 - 1. Tool material - MK8

Claims (1)

A method of producing a multilayer coating for a cutting tool, comprising vacuum-plasma coating layers, characterized in that the coating layers are applied horizontally in the same plane by three cathodes, using two oppositely arranged cathodes of titanium and a composite cathode of titanium and molybdenum located between them and a lower layer of titanium nitride is applied at a temperature of 620 ± 10 ° C, and a top layer of titanium nitride and molybdenum at a temperature of 550 ± 10 ° C.