Etching a substrate: processes – Etching to produce porous or perforated article
Reexamination Certificate
1998-06-10
2001-04-10
Gulakowski, Randy (Department: 1746)
Etching a substrate: processes
Etching to produce porous or perforated article
C075S010190, C427S309000, C427S258000
Reexamination Certificate
active
06214247
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION
The present invention relates to a method for etching composite material substrates and other substrates, and also is directed to a method for applying wear-resistant and other coatings to composite material substrates and other substrates. The present invention also relates to composite material substrates, which are comprised of particles of a hard constituent phase in a binder material phase that binds together the hard constituent particles, having wear-resistant and other coatings. The present invention finds application in any field in which it is advantageous to enhance the adhesion of a wear-resistant and other types of coatings to substrates. Examples of fields of application of the present invention include the manufacture and treatment of dies used in metal stamping, punching, threading, and blanking, and the manufacture and treatment of metal cutting inserts used in milling, turning, drilling, boring, and other metal removal operations.
BACKGROUND OF THE INVENTION
Composite materials comprised of particles of a hard constituent phase and a binder phase binding the particles together are common and are referred to as “composite materials” or “composite substrates” hereinafter. Such materials also may be referred to as “cemented” composite materials and include, for example, ceramics, cermets, and cemented carbides. Cemented carbides, include, for example, materials composed of a hard particulate material such as, for example, particles of one or more of tungsten carbide (WC), titanium carbide (TiC), titanium carbonitride (TiCN), tantalum carbide (TaC), tantalum nitride (TaN), niobium carbide (NbC), niobium nitride (NbN), zirconium carbide (ZrC), zirconium nitride (ZrN), hafnium carbide (HfC), and hafnium nitride (HfN) cemented together by a binder phase that is composed predominantly of one or more of cobalt, nickel, and iron.
Metal cutting inserts fabricated from composite materials are commonly used in chip cutting machining of metals in the metal machining industry. Metal cutting inserts are commonly fabricated from particles of metal carbide, usually tungsten carbide with the addition of carbides of other metals such as, for example, niobium, titanium, tantalum, and a metallic binder phase of cobalt or nickel. The carbide materials provide high strength but still may wear quickly when used in, for example, milling and other metal machining operations. By depositing a thin layer of wear-resistant material on the working surfaces of cemented carbide cutting inserts it is possible to increase the wear-resistance of the inserts without adversely affecting toughness. Commonly used wear-resistant cemented carbide insert coatings include, for example, TiC, TiN, TiCN, and Al
2
O
3
. Such wear-resistant coatings reduce the erosion and corrosion of the inserts' binder material.
The utility of coated composite materials such as coated cemented carbides is limited by the strength of adhesion of the wear-resistant coating to the composite material. Absence of strong adhesion between wear-resistant coatings and metal cutting inserts causes delamination of the coatings from the inserts, decreasing the inserts' service life. The presence of cobalt at the inserts' surfaces also increases the tendency of the coatings and substrates to experience delamination during use. Accordingly, it would be advantageous to provide a novel method for increasing the adhesion of wear-resistant coatings to composite materials. More broadly, it would be advantageous to enhance the adhesion of wear-resistant coatings and other types of coatings to composite material and other types of substrates.
SUMMARY OF THE INVENTION
The present invention provides a method for removing a portion of the binder phase from a substrate that is composed of at least particles of a first phase joined together by the binder phase. The present method includes the step of etching at least a portion of a surface of the substrate by contacting the surface with a gas flow that is composed of at least an etchant gas and a second gas for a time period that will allow for removal of the desired amount of binder phase. The second gas comprises one or more gases that will not react with the substrate or the removed binder material and that will not alter the oxidation state of the substrate during the etching step. Preferably, the second gas is one or more gases that will not react with the substrate or the removed portion of binder material to form deposits of a phase of W
x
Co
y
C (wherein x=3-9 and y=2-6), also referred to herein as an &eegr; (eta) phase, on the substrate.
The etchant gas used in the present method may be any gas or combination of gases that will suitable remove the desired portion of the binder phase from the substrate during the etching step. Possible etchant gases include hydrogen chloride gas, H
2
F
2
gas, and gaseous forms of any of the Group VIIA elements. Other possible etchant gases useful in the present method will be apparent to those having ordinary skill once apprised of the present invention. The second gas may be, for example, one or more gases selected from nitrogen gas, helium gas, argon gas, and neon gas. Preferably the gas flow is applied to the substrate during the etching step by introducing a flow of the etchant gas concurrently with a flow of the second gas into a chamber containing the substrate at a pressure and temperature, and for a time, that will result in removal of the desired portion of the binder phase. In one particular application of the present method, the gas flow consists of concurrent flows of hydrogen chloride gas and nitrogen gas.
Preferably, during the etching step binder phase is removed from a surface of the substrate to a depth of between about 3 microns to about 15 microns, and more preferably to a depth of between about 4 microns to about 6 microns.
The method of the present invention preferably is applied to substrates composed of a composite material comprising particles of a hard constituent material joined together by a binder material. Examples of such composite materials include cemented carbides and cermets. Examples of the binder material of such composite materials include materials composed of one or more materials selected from cobalt, nickel, iron, elements within Group VIII of the periodic table, copper, tungsten, zinc, and rhenium. Once apprised of the details of the present invention, one of ordinary skill in the substrate coating and treatment arts will comprehend additional composite materials to which the present invention may be applied.
The present invention also is directed to a method for applying a coating to at least a portion of the surface of a substrate, preferably a composite substrate that includes hard constituent material particles joined together by a binder. The method is carried out by removing a portion of the binder from a surface of the substrate by contacting the surface with a gas flow including an etchant gas and a second gas for a period of time that will remove the desired portion of binder. The surface etching effect of the etchant gas provides an etched surface on the substrate, and the etched surface will include voids produced as the binder is etched away from between hard constituent particles. The second gas is one or more gases that will not react with the substrate or the portion of the binder removed from the substrate, and that will not change the oxidation state of the substrate during the etching process. Preferably, the second gas will not react during the etching process to form eta phase within the voids etched in the substrate's surface. In a subsequent step of the method, a coating is applied to at least a portion of the etched surface. At least a portion of the coating is deposited within at least a portion of voids on the etched surface created by removal.
Thus, the etching
Bost John
Leverenz Roy V.
Gulakowski Randy
Olsen Allan
Pugh R. J.
TDY Industries, Inc.
Viccaro P. J.
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