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Coatings for cutting tools

a technology of cutting tools and coatings, applied in the field of cutting tools, can solve the problems that titanium is not the only suitable metal for carbonitride coatings, and achieve the effect of improving the adherence and fatigue strength of ceramic coatings

Inactive Publication Date: 2005-01-06
LEVERENZ ROY V +2
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0007] Briefly, according to this invention, there is provided a cutting tool insert comprising a hard metal substrate having at least two wear-resistant coatings. One of the coatings is a ceramic coating. An intermediate coating under the ceramic coating is comprised of carbonitride having a nitrogen to carbon atomic ratio between about 0.7 and about 0.95 whereby the carbonitride coating forms fingers interlocking the ceramic coating, thus improving the adherence and fatigue strength of the ceramic coating. Preferably, the nitrogen to carbon atomic ratio in the carbonitride coating lies between about 0.75 and 0.95 as determined by X-ray diffraction. The cutting tool insert also may include an additional coating, deposited on the substrate, that is a layer of at least about 2 microns, and preferably at least about 2 up to about 5 microns, in thickness and comprises at least one of a metal carbide, a metal nitride, or a metal carbonitride of a metal selected from zirconium and hafnium.
[0014] According to another aspect of the invention, there is provided a cutting tool insert including a hard substrate and a plurality of coatings on at least a portion of the substrate. The substrate may be any type suitable for use as a cutting tool insert and may be, for example, a cemented carbide as described above. The plurality of coatings includes at least a first and a second coating. The first coating is a layer at least about 2 microns and preferably about 2 to about 5 microns in thickness deposited on the substrate and includes at least one a metal carbide, a metal nitride, or a metal carbonitride of a metal selected from zirconium and hafnium. Preferably, the first coating is a layer of zirconium nitride or hafnium nitride. The second coating is a layer including at least one of a metal carbide, a metal nitride, or a metal oxide of a metal selected from groups IIIA (B, Al, Ga), IVB (Ti, Zr, Hf), VB (V, Nb, Ta), and VIB (Cr, Mo, W) of the periodic table. One or more additional layers optionally may be provided intermediate the first and second coatings and also may be deposited exterior to the second coating. Thus, for example, the plurality of coatings may include a reinforcing coating, as described herein, provided intermediate the first and second coatings. The intermediate coating contacts and enhances adhesion of the second coating. More particularly, the intermediate coating may be a layer including a metal carbonitride that, as described herein, has a nitrogen to carbon atomic ratio that results in superior adherence of the second coating due to the development of interlocking fingers between the second coating and the intermediate coating.

Problems solved by technology

Titanium is not the only suitable metal for use in the carbonitride coating.

Method used

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  • Coatings for cutting tools
  • Coatings for cutting tools
  • Coatings for cutting tools

Examples

Experimental program
Comparison scheme
Effect test

example i

COMPARATIVE EXAMPLE

[0026] A tungsten carbide based substrate (94% tungsten carbide, 6% cobalt) of K20 material (K20 is a designation of the type of hard cutting material for machining as set forth in ISO Standard ISO513:1991(E) classified according to the materials and working conditions for which the hard metal cutting material can appropriately be used) was coated according to well-known procedures in a Bemex Programmat 250 coating furnace. The coating process known as chemical vapor deposition (CVD) was used where gasses and liquids (converted to gas) are passed over substrates to be coated at 800° to 1,100° C. and reduced pressures from 50 to 900 mbar. The reactions used to coat the hard metal substrate were as follows:

CVD of TiN−uses H2+N2+Titanium Tetrachloride (TiCl4)

CVD of TiCN−uses H2+N2+TiCl4+Acetonitrile (CH3CN) or CH4

CVD of Al2O3−uses H2+HCl+Aluminum Chloride (AlCl3)+CO2+H2S

[0027] The essential coating periods and atmospheres used to apply the titanium nitride layer, th...

example ii

[0032] A coating, according to this invention, was prepared on a tungsten carbide based substrate in the coating furnace above described with the coating periods and atmospheres as described in Tables IV, V and VI.

TABLE IVRun TimeMillibar Reactor° C. ReactorCoatingMinutesPressureTemp.TiN60160920TiCN240801005Al2O3540601005

[0033]

TABLE VGas ReactantsLiter / MinuteCoatingH2N2CO2CH4HClH2STiN149TiCN11.380.6Al2O3110.60.2.050

[0034]

TABLE VIAlCl3 GasGeneratorLiquid Reactantsl / minml / minCoatingH2HClCH3CN LiquidTiCl4 LiquidTiN2.1TiCN0.9Al2O31.90.8

[0035] Tables IV, V and VI, in addition to showing the run times, reaction pressures and temperatures, show the rate of gas reactants, aluminum chloride generator reactants and the liquid reactants. The gas reactants introduced into the aluminum chloride generator flow over aluminum metal chips producing a quantity of aluminum chloride which is passed into the coating furnace.

[0036] X-ray analysis of the titanium carbonitride layer demonstrated a latti...

example iii

[0038] Example III was prepared the same as Example II except the nitrogen was lower in the coating furnace during the deposition of the carbonitride layer. The lattice spacing in the titanium carbonitride layer was found to be 1.509 which represents a nitrogen to carbon atomic ratio of 21:30 or a nitrogen content of 70%.

[0039] In the machining test, fretting was displayed only after a 5-inch cut length (estimated 40 to 50 seconds). The microstructure of Example II shown in FIG. 3 anchors between the oxide and the titanium carbonitride layers are displayed but are very minor.

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Abstract

A cutting tool insert comprises a hard metal substrate having at least two wear-resistant coatings including an exterior ceramic coating and a coating under the ceramic coating being a metal carbonitride having a nitrogen to carbon atomic ratio between 0.7 and 0.95 which causes the metal carbonitride to form projections into the ceramic coating improving adherence and crater resistance of the ceramic coating. Also disclosed is a cutting tool insert including a hard substrate and at least first and second coatings on at least a portion of said substrate. The first coating is of at least about 2 microns, is in contact with the substrate, and includes at least one of a metal carbide, a metal nitride, and a metal carbonitride of a metal selected from the group consisting of zirconium and hafnium. The second coating may include at least one of a metal carbide, a metal nitride, and a metal oxide of a metal selected from groups IIIA, IVB, VB, and VIB of the periodic table.

Description

FIELD OF THE INVENTION [0001] The present invention relates to the field of cutting tools and particularly to coatings for ceramic coated hard metal cutting tool inserts used for cutting, milling, drilling and other applications such as boring, trepanning, threading and grooving. BACKGROUND OF THE INVENTION [0002] Coatings improve the performance of cutting tools, especially ceramic or oxide coatings on carbide or hard metal cutting tools. Ever since carbide cutting tool inserts have been ceramic coated with, for example, aluminum oxide (Al2O3), there has been a continuing effort to improve the adherence of the coating to the substrate. When the first aluminum oxide coating was applied directly to a substrate of the carbide or hard metal type, the oxygen in the aluminum oxide reacted with the substrate which reduced the adherence. [0003] It has been known to improve the properties of tool inserts made from a sintered hard metal substrate (metallic carbide bonded with a binder metal)...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C23C16/36C23C30/00
CPCC23C16/36C23C30/005Y10T428/24975Y10T428/24942Y10T428/12785Y10T428/12792Y10T428/265Y10T407/27Y10T428/2982
Inventor LEVERENZ, ROY V.BOST, JOHNOAKES, JAMES J.
Owner LEVERENZ ROY V
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