Coating processes – Coating by vapor – gas – or smoke
Reexamination Certificate
1999-11-26
2002-06-25
Chen, Bret (Department: 1762)
Coating processes
Coating by vapor, gas, or smoke
C427S255120, C427S569000, C427S586000, C204S471000, C204S484000
Reexamination Certificate
active
06410086
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to the formation of surface coatings, and more particularly, to a method for forming on an object a high performance surface coating, characterized by high mechanical strength, exhibiting hardness and wear resistance, stability at high temperatures, and resistance to chemical attacks, and to compositions of the high performance surface coatings.
Currently, there is an on-going search for methods for forming surface coatings characterized by high mechanical strength, exhibiting hardness and wear resistance, stability at high temperatures, and resistance to chemical attacks, and for compositions of such surface coatings. High performance surface coatings are necessary for manufacturing objects used in high performance applications, including devices such as instruments, tools, equipment, machines, components of each of these, and work pieces.
There is a wide range of applications for high performance coated objects, each of which involves one or more forms of extensive or high levels of physicochemical phenomena or interactions taking place at or on the coated surface of a given object, involving an object and a work piece, two objects, an object and its local environment, or a combination of these. These forms include mechanical phenomena such as friction, abrasion, and related mechanisms involving hardness and material wear, thermal phenomena such as heat generation, absorption, and transfer, and chemical phenomena such as oxidation, corrosion, or reaction between materials. Applications which use high performance surface coated objects include, for example, devices, components, and work pieces, involving cutting, grinding, milling, drilling, polishing, rotating, or turning, used in a diversity of industries such as mining, metal working, construction, medical and aeronautical applications, and power generation.
High performance applications also include using coated objects such as rotators, ball bearings, gears, pistons, and blades, in larger objects or devices such as generators, motors, and turbines, used for example, in land, sea, and air vehicles such as automobiles, boats, and airplanes, and for example, in electric power stations.
There is an increasing need for objects with high performance surface coatings, both for effecting processes and as components, in the semiconductor, electronics, and electro-optics industries. An example is the manufacture of electronic components having a high performance coated surface, for maintaining functionality during conditions of high levels of heat radiation or heat absorption, used in larger electronic equipment and instrumentation.
In objects having a high performance coated surface, the active region where the extensive physicochemical phenomena or interactions take place is characterized by the volume encompassing the active or coated surface area extending along an edge or contour of the coating and penetrating into the surface coating to a depth usually of less than 250 microns. But the volume extend to a depth of the order of 1000 microns. This can be considered the high performance surface coated region, and is typically composed of at least one layer of one or more coating materials, formed by one or more methods for coating the surface of the object.
Base materials currently used for manufacturing objects used in high performance applications, upon which surface coatings are formed, include (i) metals alloys such as ferrous and non-ferrous alloys, for example, steel or tungsten alloyed with transition group metals such as cobalt or nickel; (ii) metal carbides such as tungsten carbide, titanium carbide, tantalum carbide, or niobium carbide; (iii) metal nitrides such as titanium nitride, tantalum nitride and hafnium nitride; (iv) metal borides such as titanium boride, tantalum boride, and hafnium boride; (v) cemented carbides featuring a metal carbide cemented by one or more transition group metals such as iron, cobalt, and nickel; (vi) oxide and non-oxide ceramics such as alumina or silicon nitride; (vii) cermets or ceramic metal composites featuring a ceramic bonded to a metal such as transition group metals cobalt, nickel, or molybdenum; and (viii) semiconductor materials and oxides such as silicon or silicon dioxide.
Base materials of high performance objects typically include a relatively small concentration of one or more base material strengthening or enhancing agents, where each strengthening or enhancing agent exhibits at least one particular physicochemical property or characteristic, desirably transferable to the base material, in order to improve object properties, function, and/or in service durability. Base material strengthening or enhancing agents include (i) at least one of the above listed base materials to be used in combination with the base material of the object. Additional base material strengthening or enhancing agents include (ii) non-metal carbides such as silicon carbide, (iii) non-metal nitrides such as silicon nitride and boron nitride, and (iv) metal carbide
itride mixtures such as titanium carbonitride.
For further enhancing mechanical, thermal, and chemical properties and characteristics of a base material of a high performance object, or of a base material, which includes a strengthening or enhancing agent, a coating of usually less than about 250 microns is formed on the surface of the base material of the object. Typical surface coating materials are selected from any of the above listed base materials, base material strengthening agents, or diamond, and applied to a selected base material surface, using specialized methods and procedures.
A wide variety of methods for forming a coating on an object for a high performance application exists. Such methods, including chemical vapor deposition (CVD), plasma chemical vapor deposition (PCVD), plasma assisted chemical vapor deposition (PACVD), chemical vapor infiltration (CVI), laser techniques, and electrophoretic deposition (EPD), the advantages, scope of application, and limitations of each, are well described and taught in the patent literature.
Limitations exist with respect to forming high performance surface coatings on objects to be used in high performance applications. It is of prime importance that the surface coating be mechanically strong exhibiting hardness and wear resistance, and be thermally and chemically durable, as well as adhering to the surface coating substrate. Moreover, it is important for the surface coating to exhibit these same properties and characteristics under working conditions of a given application. These attributes of coated objects are strongly influenced and limited by the coating method, where each method involves the selection of coating parameters such as particular temperatures required for the coating process, geometrical conformation to the shape of a particular substrate, as well as coating thickness, density, uniformity, and adhesion to a base material substrate. Additionally, the rate of coating formation is an important processing parameter when scaling-up a coating method for inclusion into a time dependent production line for the manufacture of a high performance object.
Using any known method for forming a coating on a surface of an object serving as a substrate typically results in attaining several but not all desirable attributes needed for high performance applications. For example, the rate of coating formation may be high, but the coating may be insufficiently dense. Similarly, a coating may be sufficiently thick or dense, yet the coating may not sufficiently adhere to the substrate surface. Additionally, a rapidly formed coating of sufficient thickness and density may not possess the proper combination of physicochemical properties for high performance in service durability, as described below for the case of a thick diamond coating limited by chemical activity at high temperatures. These are significant limitations with respect to current methods for coating objects for use in high performance applications.
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Barsky Alex
Brandon David G.
Cherniak Ludmilla
Gal-Or Leah
Gilboa Shay
Cerel (Ceramic Technologies) Ltd.
Chen Bret
G. E. Ehrlich Ltd.
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