NO851558L - APPLICATION OF A COVER TO CUTTING TOOL. - Google Patents

Description

The present invention generally relates to metalworking and more particularly to the application of coatings.

The modern trend in metalworking requires higher strength, wear resistance and less expensive materials for the manufacture of tools.

However, a further modification of the composition of the tool materials does not bring any significant improvement regarding the physical and mechanical properties. The problem can therefore be solved by more advanced methods for applying resistant and wear-resistant coatings.

A method is known for applying a coating to a base of carbonaceous material by vaporizing a carbide-forming material under reduced pressure, heating the working surface of the base material and condensing the vaporizable carbide-forming material on until a coating is formed (see V.I.Kostikov and J.A.Shesternev "Plazmennye pokrytia", the Metallurgia Publishers, Moscow, 1978, 1978, p.24). According to this method, evaporation of the carbide-forming material and the heating of the working surface of the base material are carried out thermally.

A shortcoming of this method is that the carbidization treatment of the vaporizable material with carbon of the base material takes place at a temperature from 1000 to 1600°C, which complicates the formation of the coating.

In addition, a further shortcoming of this method lies in the fact that the vaporizable material does not completely react with the carbon in the base material to affect the quality of the coating formed.

A further known method for applying a coating to cutting tools predominantly with a base of carbonaceous material involves vaporizing at least one carbide-forming

important information

For archival reasons, the Norwegian Patent Office only has access to documents for this generally available patent application that contain handwritten notes, comments or crossing outs, or that may be stamped "Expired" or the like. We have therefore had to use these documents for scanning to create an electronic edition.

Handwritten remarks or comments have been part of the proceedings, and must not be used to interpret the content of the document.

Cross-outs and stampings with "Expired" etc. indicates that newer documents have been received during the proceedings to replace the earlier document. Such crossing out or stamping must not be understood as meaning that the relevant part of the document does not apply.

Please ignore handwritten remarks, comments or crossing outs, as well as any stamps with "Expired" etc. which have the same meaning. material by arc discharge under negative pressure, applying voltage to the cutting tool being processed and cleaning and heating the working surface of the base material for the cutting tool by bombarding the carbide-forming material with ions with a view to subsequent condensation on the working surface of the base material until the coating is formed. According to this method and before the condensation of ions on the volatile carbide-forming material, a gas mixture is introduced under reduced pressure, a mixture that tends to react with the volatile carbide-forming material until the coating is formed and the working surface of the base material of the cutting tool, cf. "Fizika i khima obrabotki materialov "Periodical; A.A.Andreev et al "Pokrytia iz karbida molybdena, poluchennye metodom osazhdenia plazmennykh potokov v vakuume" - in Russian, "Nauka" Publishers, Moscow, No. 2, p. 169).

However, the introduction of a gas mixture causes strong complications in this process and results in a longer period of time which is necessary for the formation of the coating.

According to the method, the course of vaporization of the gas mixture by arc discharge is not stable, which results in continuous variations of the composition of the coating, which therefore makes it more difficult to reproduce the required composition of the coating, which in turn makes the coating formation process more complicated.

Furthermore, the use of explosive gases for the gas mixture can put work personnel at risk.

The invention is aimed at providing a method for applying a coating where cleaning and heating of the working surface of the base material in a cutting tool being processed is carried out in order to simplify the method for coating formation, and where the risk of explosion

be prevented.

The object of the invention is achieved in that in a method for applying a coating, preferably on cutting tools, of carbonaceous materials, v-t± vaporization of at least one carbide-forming material under vacuum during arc discharge, application of voltage to the cutting tool, cleaning and heating of the surface of the base material of the cutting tool by cathodic bombardment with ions of the vaporizable carbide-forming material, accompanied by a subsequent condensation of this on the working surface of the base material of the cutting tool until the coating is formed thereon according to the invention cleaning and heating of the working surface of the base material in the cutting tool until a temperature is reached where carbidization of the vaporizable carbide-forming material by means of carbon in the base material of the cutting tool takes place.

Preferably, the temperature at which carbidisation takes place is between 500 and 540°C where steel is used as the base material for the cutting tool.

As a reference, the temperature for carbidization will be from 620 to 680°C when a hard alloy is used as the base material for the cutting tool.

Titanium is preferably used as evaporable carbide-forming material.

Alternatively, titanium nitride is used as evaporable carbide-forming materials.

Most preferably, a titanium alloy is used as evaporable vessel-bii^clanting material.

When two carbide-forming materials are used at the same time, molybdenum is a preferentially used material as the additional

are caride-forming material.

The invention makes it possible to stabilize the composition of a coating that is applied, expressed in terms of thickness, which simplifies the method of applying such coatings.

In addition, the method of the invention makes it possible to prevent the risk of explosion during application.

A method for applying a coating to essentially cutting tools whose base metal contains carbonaceous material is that a carbide-forming material is vacuum-evaporated by spark discharge and an electrical voltage is applied to the cutting tool. Then, the a^id surface of cutting tool base metal is cleaned and heated by bombardment in ions of decarbide-forming material to a temperature so that carbidizing treatment of the carbide-forming material is vaporized with carbon from the base metal of the cutting tool. Thereafter, the ions from the vaporized carbon-forming material tend to condense on the working surface of the base material in the cutting tool until the coating is formed.

According to a feature of the proposed method, the temperature at which the carbonisation treatment takes place is between 500 and 540°C to ensure a greater saturation of the coating which is formed with the help of carbon, in which steel is used as the base material.

At a carburizing treatment temperature below 500UC, no coating formation with carbon takes place in practice, while at a temperature above 540°C the steel tends to partially lose its strength, which in both cases affects the wear resistance of the cutting tool.

Alternatively, for greater saturation of coatings formed using carbon, and according to the proposed method,

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is the temperature at which the carburizing treatment takes place, from 620 to 680°C, whereby a hard alloy is preferably used as the base material.

At a carbidization temperature below 620°C and above 680°C, processes similar to those described above occur in the case of hard alloys.

According to another feature of the invention, titanium is used as carbide-forming material which is evaporated.

In order to increase the wear resistance of the coating that is formed, a titanium alloy is preferably used as the carbide-forming material that evaporates.

According to a further feature of the method of the invention, molybdenum is used as an additional carbide-forming material to be evaporated where two such are used.

The invention will be better understood from the numerous examples of their implementation as described below.

Example 1

A coating was applied to drills with a diameter of 5 mm.

Titanium was used as the carbide-forming material that was to be evaporated, while the following composition was used as the base material for the boron steel:

The cleaned drill bits were placed in special magazines which were filled in vacuum chambers equipped with a titanium cathode. When the vacuum value reached 10 pascals, an arc discharge was initiated and a voltage of 1500 volts was applied to the drills. Thereby, a cleaning of the working surface of the drills was carried out by cathode bombardment with titanium ions and heating to a temperature of 520°C, controlled by means of an infrared pyrometer to -10°C. Then the voltage was reduced to 250 volts to effect condensation of titanium ions on the areid surface of the drills for three minutes followed by carbidization of this surface by means of carbon on the steel. After the thickness of the thus applied coating, titanium carbide, amounted to 2 mm, the voltage was removed from the drills and the arc discharge de-energized, after which the drills were cooled to room temperature.

Wear tests of the coated drill bits were carried out on a steel with the following composition:

the following conditions:

drilling speed V = 32 m/min;

Boring feed rate S = 0.12 mm/rev.;

table depth 1 = 3d = 15 mm;

The test results are given in Table 1.

Example 2

Coatings were applied to cutting plates. As plate base material, a hard alloy with the following composition was used:

Titanium was used as evaporated material.

The coating was applied in a manner similar to that described with reference to example 1, except that the cleaning of the working surface of the plates by cathodic bombardment with titanium ions was carried out by heating to a temperature of 620°C.

An additional cutting board was tested for wear from each batch of boards that were coated; the conditions were as follows:

cutting speed V = 160m/min.

feed rate S =0.3 mm/rev.

cutting depth t =1 mm.

The test results are given in Table 2.

Example 3

Coating was applied to drill bits with a diameter of 5 mm.

Titanium nitride was used as carbide-forming material, the base material had a composition similar to that in example 1.

The working surfaces of the drills were cathodically bombarded with titanium nitride ions and heated to a temperature of 510°C. Then the applied voltage was reduced to 300 volts so that the titanium nitride ions could condense on the working surface of the drills for three minutes with subsequent carbide-

sering with the steel's carbon. The thickness of the coating, consisting of titanium carbonitride Ti(NC), was 2 microns. The voltage was then removed from the drills and the arc discharge de-energized. The drills were then cooled to room temperature and tested in the manner described in example 1.

The test results are given in Table 3.

Example 4

Cutting boards were coated.

Titanium nitride was used as material to be evaporated. The plate base material corresponded in composition to that used in example 2.

The coating application was carried out essentially as described in Example 3, except that the cathodic bombardment of the working surface of the plates with titanium nitride ions was achieved by heating to a temperature of 635°C.

Example 5

The thus coated cutting boards were tested as described in example 2. The test results are given in table 4.

Example 5

The coating was applied to drills with a diameter of 5 mm.

A titanium alloy with the following composition was used as the carbide-forming material to be evaporated:

The base material was steel with a composition as stated in example 1.

Coatings were applied essentially as described in example 1, except that cleaning of the working surface of the drills by cathodic bombardment with titanium, aluminum and molybdenum ions was accompanied by heating to a temperature of 525°C, the composition of the coating being titanium carbide based multi-alloy solid solution (Ti, Mo, A1)C.

The drills that were coated in this way were tested as in example 1.

Test results are given in Table 5.

Example 6

Coatings were applied to cutting plates.

Titanium alloy was used as carbide-forming material which evaporates, whereby the composition of this material is represented in example 5. A hard alloy with a composition as described in example 2 was used as base material.

The coating procedure was similar to that described in Example 2 except that cleaning of the working surface of the drills by cathodic bombardment with titanium, aluminum and molybdenum ions was accompanied by heating to a temperature of 650°C.

The coated plates were tested as described in example 2.

The results are shown in table 6.

Example 7

Drills with a diameter of 5 mm were coated.

Titanium and molybdenum were used as carbide-forming volatile materials. A steel with the composition described in example 1 was used as the base material.

The cleaned plates were placed in special magazines and placed in vacuum chambers equipped with two anodes consisting of titanium and molybdenum.

When the vacuum reached 5 x 10"^ mm Hg, a voltage of 1500 volts was applied to the plates and an arc discharge was initiated. Cleaning of the working surface of the plate by cathodic bombardment with titanium ions and simultaneous heating to a temperature of 680°C, regulated by infrared pyrometer to an accuracy of +10°C, was carried out. Then the applied voltage was reduced to 250 volts. Then, by alternately energizing titanium and

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the molybdenum cathodes, titanium and molybdenum ions condensed for three minutes. A multilayer coating of alternating layers of titanium carbide TiC and molybdenum carbide MO 2 C was obtained. The voltage on the drills was removed and the arc discharge de-energized, after which the drills were cooled in chambers to room temperature.

Drilling tests were carried out as described in example 1.

The results are shown in table 7.

Example 8

Cutting boards were coated.

Titanium and molybdenum were used as evaporable carbide-forming materials. A hard alloy with a composition as described in example 2 was used as the base material.

A multi-layer coating was applied as indicated in Example 7, except that cleaning of the working surface of the plates by cathodic bombardment with titanium and molybdenum particles was carried out at a temperature of 680°C.

The cutting plates were then tested as in Example 2.

The results are shown in table 8.

The test results as set forth in Examples 1 to 8 show that a simplification of the coating application processes made it possible to increase the wear resistance of drills and cutting plates.

The method according to the invention makes it possible to condense coatings in an amount of 0.1 to 0.7 microns per minute, which in turn cuts down the time for the process cycle.

The invention finds application in achieving wear-resistant durable coatings on cutting tools and punching tools made of carbon-containing materials such as steel, hard alloys, ceramic alloys, etc.

Claims (6)

1. Process for applying a coating mainly to cutting tools that essentially consist of carbonaceous material by vaporizing at least one carbonaceous material under pressure by means of discharge, applying a voltage to the cutting tool, cleaning and heating the working surface of, the base material -i— det^ te-e" by cathodic bombardment with \ions of vaporizable carbide-forming material to a temperature at which it reacts with the base material in the cutting tool, followed by subsequent condensation on the working surface of the material until a coating is formed, characterized in that the temperature at which the carbide-forming material reacts with the base material in the tool during the cleaning and the heating is equal to the temperature at which the carburizing treatment of the vaporizable carbide-forming material with the carbon in the base material in the cutting tool takes place, while "high gones" of the carbide-forming material are condensed simultaneously with their carbidization which a chain reaction of carbon transfer through the thickness of the coating layer. 2. Method according to claim 1, characterized in that a carbidization temperature between 620 and 680°C is used when a hard alloy is used as the base material in the cutting tool. 3- Method according to claim 1, characterized in that titanium is used as evaporable carbide-forming material. 4. Method according to claim 1, characterized in that titanium nitride is used as evaporable carbide-forming material. 5. Method according to claim 1, characterized in that a titanium alloy is used as evaporable carbide-forming material. 6. Method according to claim 3, characterized in that two carbide-forming materials are used, using molybdenum as the further vaporizable carbide-forming material.