WO2007115043A2

WO2007115043A2 - Valves having corrosion resistant ceramic coating

Info

Publication number: WO2007115043A2
Application number: PCT/US2007/065373
Authority: WO
Inventors: David R. Burton; Jeffrey C. Holm; James M. Yates
Original assignee: High Performance Coatings Inc.
Priority date: 2006-03-29
Filing date: 2007-03-28
Publication date: 2007-10-11
Also published as: WO2007115043A3; WO2007115043A8

Abstract

An inlet valve is partially coated with a protective coating to resist corrosion and gas impingement when used in an internal combustion engine. The inlet valve has a hard cladding that is shaped to function as a valve seat. The hard cladding forms an interface with the valve head body, which is typically made of a softer metallic mierial than the hard cladding. The protective coating is bonded to the inlet valve and covers the cladding-body interface. The protective coating is resistant to corrosion, wear from gas impingement, and can withstand the high temperatures reached in internal combustion engines. A method for making the inlet valves generally includes masking a portion of the valve stem and the valve seat, applying a protective coating to cladding-body interface, and curing the protective coating or otherwise bonding the protective coating to the inlet valve.

Description

VALVES HAVING CORROSION RESISTANT CERAMIC COATING AND METHODS AND SYSTEMS FOR MANUFACTURING SAME

BACKGROUND OF THE INVENTION

1. The Field of the Invention The present invention relates to inlet valves used in internal combustion engines. More particularly, the present invention relates to inlet valves coated with a high temperature coating and methods and systems for manufacturing the valves.

2. Related Technology

Internal combustion engines are used in many different applications, such as automobiles, ships, electric generators, pumps, among others. Inlet valves are a common component of many internal combustion engines. The inlet valves are positioned in an inlet port to close the air intake during combustion. During the air intake stroke, a cam pushes the inlet valve open and allows the fuel mixture to enter the combustion chamber. The seal that the inlet valve makes with the inlet port is important to engine performance and efficiency. If the valve leaks the pressure in the combustion chamber decreases and the engine generates considerably less power. Engine manufacturers over the last few decades have dedicated substantial efforts in designing inlet valves that can form a tight seal with the valve seat of the inlet port. Figure 1 shows a typical inlet valve 10. The body of inlet valve 10 includes a valve head 12 and a valve stem 14. The valve head 10 has a valve seat 16 that is shaped and configured to engage an inlet port to seal a combustion chamber. The valve seat is particularly crucial for the reliability of the inlet valve. It is well-known that corrosion of the seat face can cause the valve to leak when the valve is closed, which results in "burn through."

To prevent burn through, the valve seats on the inlet valve and the inlet port have been made with increasingly harder materials. The valve seat is made harder by applying a hard cladding layer on the valve head and machining to make the valve seat. The hard cladding makes the valve seat 16 more wear-resistant and reduces the formation of dent marks. Examples of materials that are frequently used for valve seat materials are metal alloys having cobalt and nickel (e.g., Stellite).

The use of extremely hard materials for valve seats has dramatically improved the performance and durability of inlet valves. However, in almost all cases, the advantages of using these hard materials throughout the valve (e.g., in the valve stem and other parts of the valve head) are not sufficient to offset the increase in price over softer metals such as low carbon steel. Consequently the valve stem 14 and the bell region 18 between the seat face 20 and the valve stem 14 are typically made from low carbon steel.

Improvements in the durability of the seat face of inlet valves has allowed inlet valves to hold up under more severe conditions and for longer periods of time than previous inlet valves. In many cases, the seat face is no longer the location where the valve fails. One point of failure observed in inlet valves occurs at the interface where the hard seat material ends and the softer steel of the valve body begins. Gas impingement and/or corrosion can pit or otherwise wear down the material in the valve body over extended periods of time. Wear is particularly likely to happen at the interface because of the transition between the two types of metals and the superior quality of the valve seat material. Failure at the interface between the harder seat material and the softer valve body material is particularly problematic in engines that use exhaust gas recirculation (EGR). EGR is used to recycle gases that have high quantities of unburned particulate, NO_x, and/or SO_x back into the combustion chamber to be reburned. The hot and corrosive exhaust gases are mixed with outside air and enter the combustion chamber by passing around the valve head of the inlet valve. Consequently, the recycled exhaust gases come into contact with the bell region 18 of the inlet valve 10. Furthermore, condensation during shutdown can cause pooling of corrosive liquids such as sulfuric acid on the valve. Corrosion and/or gas impingement can weaken bell region 18, and in particular the valve body material at the interface with the hard seating material. Even where a portion of the bell is coated as in U.S. patent number 5,662,078, corrosive gases in contact with the valve body material at the seat-material, body-material interface can cause pits and cracks to form that lead to valve failure at the interface.

In addition, many of the currently available ceramic coatings and methods for applying ceramic coatings to engine parts are difficult and expensive to carry out. The time and temperatures at which many ceramic coatings are applied can significantly increase the cost. For example, many ceramic coatings require a sintering step that is performed at 1600-2500 ⁰F for an extended period of time. The energy required to perform the sintering step can make applying the coating cost prohibitive. Another problem with applying a ceramic coating is the need to apply the coating evenly. If the coating runs or pools, even a coating that is initially applied in an even manner can become uneven before it is baked in place. BRIEF SUMMARY OF THE INVENTION

The present invention relates to inlet valves that use a hard cladding material to make the valve seat. It has been found that the interface between the cladding and the body of the valve head is particularly susceptible to wear from gas impingement and/or corrosion. The inlet valves of the present invention include a protective coating that covers the cladding-body interface to improve the durability of the inlet valve. This is particularly true in the case where the inlet gases are corrosive (e.g., gas from an EGR system that contains NO_x and SO_x).

In an exemplary embodiment, the inlet valve includes a valve head connected to a valve stem. The valve head includes a valve head body comprising a metallic material and a cladding covering a portion of the valve head body. At least a portion of the surface of the cladding forms a valve seat. The cladding and the metallic material abut one another, thereby forming a cladding-body interface. A protective coating is bonded to the valve head and covers the cladding-body interface. The protective coating typically comprises a ceramic of one or more metal oxides, nitrides, and optionally doped with ground state metals.

In a preferred embodiment, the protective coating is wider than the cladding- body interface by at least about 5 thousands of an inch on both sides, more preferably at least about 15 thousands of an inch, and most preferably at least about 30 thousands of an inch on both sides of the interface. Extending the coating beyond the interface can be advantageous because it provides a barrier that is more difficult for hot gasses to penetrate. If the coating wears down over time, the excess overlap ensures that the full thickness of the coating must be worn through before the cladding-body interface will be exposed to hot corrosive gases. Another advantage of extending the coating beyond the cladding-body interface is to ensure that the cladding-body interface is adequately covered if there are variations in manufacturing tolerances. Typically the location of the edge of the coating is limited by tolerances available for a particular manufacturing technique. By extending the coating beyond the cladding-body interface, the cladding-body interface is more likely to be covered if the edge of the coating or the cladding-body interface deviates by an amount within the allowed tolerances.

Preferably the protective coating continuously overlaps the entire cladding- body interface. Covering the entire interface can be advantageous since a single pit or weak location in the valve head can lead to valve failure.

In an exemplary embodiment, the valve seat cladding comprises a hard metal alloy suitable for use as a valve seat material. Examples of suitable alloy materials include nickel and/or cobalt alloyed with one or more metals selected from the group of chromium, aluminum, tungsten, molybdenum, titanium, or iron. A commercially available suitable alloy is Stellite, which is a cobalt-chromium alloy. The cladding material is selected for its hardness and durability so as to be suitable for use as a valve seat material.

The valve head body and the valve stem can be made from any metal. In an exemplary embodiment, the valve head body and the valve stem are manufactured from steel, preferably low carbon steel, to minimize cost. Because the coating of the present invention can protect the valve head body and the stem from corrosive gasses, the valve head body and the valve stem can be manufactured from inexpensive materials such as low carbon steel. This is a tremendous improvement in the art as extremely low cost metals can be made highly resistant to heat and corrosion by applying a protective layer over the surface.

The invention also includes a method for coating an engine valve. In one embodiment, the method can be generally carried out by (i) providing an engine valve

(ii) preparing the engine part for coating (iii) applying a protective coating to at least a portion of the valve, and (iv) at least partially curing the protective coating using infrared radiation.

Any engine valve can be coated according to the present invention, including traditional engine valves that have a stem portion and a valve head. The engine valves used in the coating method of the present invention can be selected from any kind of combustion engine where valves are employed. The engine valves can be used with diesel engines, gasoline engines, flex fuel engines, alcohol burning engines, among others.

The engine valves are prepared for coating by cleaning the portion of the surface that is to be coated and/or roughening the surface to improve bonding. In an exemplary embodiment, the portion of the valve that is to be coated is roughened using grit blasting. Tooling is applied to the valve to mask a portion of the valve that will not be coated with the protective coating. For example, it may be desirable to leave the valve seat uncoated since the valve seat is typically made from a nickel or cobalt superalloy. The masked valve is then grit blasted to roughen the surface of the engine valve. Roughening the surface of the valve helps the protective coating bond to the metal.

In one embodiment of the invention, the protective coatings can include the following three components: (i) a metal and/or a ceramic material, (ii) a binder, and (iii) a solvent. Examples of suitable metals and ceramic materials include silicon, zinc, zirconium, magnesium, manganese, chromium, titanium, iron, aluminum, noble metals, molybdenum, cobalt, nickel, silica, calamine, zirconia, magnesia, titania, alumina, ceria, scandia, yttria, among others. Examples of suitable binders include ethylene copolymers, polyurethanes, polyethylene oxides, various acrylics, paraffin waxes, polystyrenes, polyethylenes, celluslosics, "agar," soda silicate, kairome clay, titania and aluminum phosphate, among others. Examples of suitable solvents include polar solvents such as water, methanol, and ethanol and non-polar organic solvents such as benzene and toluene.

The protective coating compositions are made by mixing a metal and/or metal oxide, a binder, and a solvent to form a paste or slurry. The metals, metal oxides, binders, and solvents are selected to give the coating a desired emissivity such that it will efficiently absorb infrared radiation. In a preferred embodiment, the emissivity of the coating composition is greater than about 0.7, more preferably greater than about 0.90, and most preferably greater than about 0.95. The protective coating composition is then applied to the engine valve in the desired location. The coating can be applied using any technique that can lay down a layer of composition having a desired thickness and uniformity. Suitable methods include spray coating, spin coating, and brushing. The engine valve can be masked prior to applying the coating composition to prevent the coating from being applied to locations that are not intended to be coated. For example, it may be desirable to mask the seat face to prevent the coating composition from being applied thereto.

The coating composition is cured using infrared radiation. The infrared radiation heats the coating layer to a temperature in a range from about 100 ⁰C to about 650 ⁰C, more preferably in a range from about 200 ⁰C to about 550 ⁰C, and most preferably in a range from about 250 ⁰C to about 450 °C. The infrared heating bonds, volatilizes, and/or burns off most or all of the solvent and optionally some or all of the binder. As the solvent and binder are removed, the metal and/or ceramic materials sinter to form a protective coating that is corrosion and heat resistant. During the curing phase, the protective coating bonds to the surface of the valve thereby forming a permanent composition barrier.

Curing the coating using infrared radiation is advantageous because the coating can be cured quickly and economically. The high emissivity of the coating efficiently absorbs the infrared radiation while other parts of the valve and/or masking do not. The masking and/or non-coated portions of the valve typically have or can be made to have low emissivity such that energy is not absorbed by these areas. One reason why the coatings of the present invention cure more quickly is because infrared radiation can penetrate the surface of the coating. Thus, the coating is cured at various depths without the need to wait for conduction of the heat through the layer. This feature is also partially responsible for the ability to cure at lower temperatures. By directing the heat at the coating, the curing temperatures can be reached without heating the entire part to a high temperature. Thus, the method for coating valves according to the present invention can be carried out more economically and quickly than by using other methods.

In a preferred embodiment, the coating cures in less than about 0.5 hour, more preferably less than about 20 minutes, and most preferably in less than about 5 minutes. The ability to cure relatively quickly and/or at relatively low temperatures can dramatically reduce the energy requirements for applying the coating. The present invention also relates to a system for applying a protective coating to a portion of an engine valve and curing the coating using infrared radiation. The system allows for mass production of coated valves by facilitating the application of an even coating and rapidly curing the coating using infrared radiation.

The system of the present invention includes at least one infrared oven and a movable track that that passes through the infrared oven. The system also includes a plurality of attachment apparatus connected to the movable track that are configured to receive and hold an engine valve on the track as the track moves. A spraying device is positioned along the movable track before the infrared oven. The spraying device is configured to apply a coating to a portion of the engine valve, which is then cured in the infrared oven. The engine valves can be masked to prevent coating of any portion of the valve that is not desired to be coated (e.g., the valve seat).

The composition that is coated on the engine valve using the spraying device is selected to have a flowability in the spraying device that facilitates an even application of the coating on the engine valve. In addition, the coating composition is curable under infrared radiation. The protective coatings of the present invention typically include the following three components: (i) a metal and/or a ceramic material, (ii) a binder, and (iii) a solvent. After the coating is applied to the engine valve, the engine valve is transported through the infrared oven. Infrared radiation from the oven heats the coating layer to a temperature in the manner described above. During the curing phase, the protective coating bonds to the surface of the valve thereby forming a permanent composition barrier. These and other advantages and features of the present invention will become more fully apparent from the following description and appended claims as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS To further clarify the above and other advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

Figure 1 is an elevational view of an exemplary inlet valve without a protective coating;

Figure 2 is an elevational view of an exemplary inlet valve having a protective coating according to the present invention; Figure 3 A is a partially sectioned view of the inlet valve of Figure 2 showing a cladding layer and cladding-body interface; Figure 3B is a partially sectioned view of the inlet valve of Figure 2 showing a cladding layer and cladding-body interface with the protective coating covering the interface;

Figure 4 is a schematic of an internal combustion engine having an EGR system and an inlet valve according to the present invention;

Figure 5 shows an exemplary inlet valve and tooling for preparing the inlet valve to be coated with a protective coating; and

Figure 6 shows the inlet valve of Figure 5 and masking tooling for application of the protective coating; Figure 7 is a schematic of a high throughput system for coating engine valves according to one embodiment of the invention;

Figure 8A is an elevational view of an attachment apparatus according to one embodiment of the invention;

Figure 8B illustrates the gear portion of the attachment apparatus of Figure 8 A being used with a stationary gear and a movable track; and

Figure 9 illustrates an assembly of an attachment apparatus, an engine valve, and a masking tooling according to one embodiment of the invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS I. INLET VALVES The present invention relates to inlet valves in internal combustion engines.

The inlet valves can be made in part from an inexpensive metal that consequently is susceptible to corrosion, especially in the region near the valve seat where the valve seat material interfaces the valve body material. A protective coating is applied to the inlet valves to reduce wear and valve failure caused by gas impingement and/or corrosion. The invention also relates to methods and apparatus for applying corrosion resistant ceramic coatings to engine valves

Figure 2 shows an exemplary inlet valve 100 that has been surface coated according to the present invention. Inlet valve 100 includes a valve head 112 that is connected to valve stem 114. On the perimeter of valve head 112, the valve head 112 is shaped to form a valve seat 116. The valve seat 116 is part of seating face 120. A protective coating 124 is bonded (i.e., adhered) to the inlet valve. In an exemplary embodiment, the protective coating 124 covers the bell region 118, a portion of stem 114, and a portion of the seating face 120. It thus overlaps the interface between cladding layer 128 and valve body 126 as shown in Figure 3B.

Figure 3 A shows an inlet valve 100 with a portion of valve head 1 12 and coating 124 cut away to reveal the underlying structure of the valve head 1 12. Valve head 112 includes a valve body 126 and a cladding 128. Valve body 126 is made from a metallic material such as steel. Cladding 128 is made from a hard material suitable for use as a valve seat (e.g., Stellite). Valve body 126 and cladding 128 abut one another to form cladding-body interface 130 on the surface of valve head 1 12. If the inlet valve is circular, the cladding-body interface will tend to be a curved line that is concentric with the seating face 120. However, the cladding-body interface need not be concentric with seating face 120. Furthermore, valve head 112 can have shapes other than "bell-shaped." During use of inlet valve 100 in an internal combustion engine, cladding-body interface 130 will be situated on the inside of the inlet port (i.e., within the air intake) when the valve is in the closed position. Figure 3B shows inlet valve 100 with a portion of valve head 112 cut away but with coating 124 extending over interface 130. Protective coating 124 is positioned over interface 130 to protect interface 130 from corrosive gasses and liquids and from gas impingement. The coating can be any desired thickness so long as the thickness does not substantially interfere with valve movement or gas flow in the air intake. In a preferred embodiment, the coating thickness is in a range from about 0.0002 inches to about 0.002 inches. The desired thickness depends on the type of coating used and the amount of material needed to provide the desired protection. Relatively thin coatings are preferred due to the decreased cost and the increased simplicity with which they can be applied. To cover cladding-body interface 130, a first edge 132 of protective coating

124 begins on cladding 128. First edge 132 overlaps cladding-body interface 130 by a desired amount. The distance between the first edge 132 and interface 130 depends on the tolerances associated with the valve seat 116, the tolerances associated with applying protective coating 124, and the potential for protective coating to wear during use. In a preferred embodiment, the first edge 132 begins on cladding 128 at least about 0.005 inches away from cladding-body interface 130, more preferably at least about 0.015 inches, and most preferably at least about 0.030 inches from cladding-body interface 130. In some cases, the valve may be very large (e.g. a valve head with a 12 inch diameter). In this case, the cladding may be substantially wider than the valve seat and the coating overlap may be substantially larger than 0.005 inches (e.g. 1 inch of overlap).

The protective coating 124 advantageously has a second edge that extends into the bell region so as to be at least about 0.005 inches away from the cladding-body interface, more preferably at least about 0.015 inches and more preferably at least about 0.030 inches. Even more preferably the protective coating 124 covers the entire bell region 118 and most preferably a portion of valve stem 114 such that the second edge 134 is positioned on valve stem 114. Typically the portion of the valve stem that will be in within a valve guide is not coated with the protective coating 124. Advantageously protective coating 124 extends from the cladding to the valve stem 114 so as to cover the entire surface of inlet valve 100 that is exposed to the gas path during use. Covering substantially the entire portion of the inlet valve 100 that is in the gas path can be advantageous because the second edge 134 will be out of the gas path and therefore less likely to receive wear from gas impingement or provide a location for the accumulation of condensed corrosive gases.

Extending protective coating 124 beyond cladding-body interface 130 is particularly advantageous for protecting inlet valve 100 against wear and failure, since the cladding-body interface 130 has been found to be particularly susceptible to weakening from corrosion and gas impingement in uncoated valves.

In most cases, protective coating 124 is not applied to valve seat 116. Valve seat 116 is the area of seating face 120 where inlet valve 100 is designed to seat during use. Typically valve seat 116 is a portion of seating face 120 near the middle of seating face 120. Seating face 120 is often wider than valve seat 116 to ensure that inlet valve 100 seats on seating face 120. Similarly, cladding 128 is typically wider than valve seat 116 to ensure that inlet valve 100 seats on cladding 128. First edge 132 of protective coating can be extended onto cladding 128 over any portion of cladding 128 that is not used to seat inlet valve 100. While protective coating 124 can be applied to valve seat 116, this approach may require further grinding of valve seat 116 and/or poor performance of the valve until coating 124 wears off of seating face 116 from use of inlet valve 100.

While Figures 2—4 show the edge of cladding 128 aligning with the edge of seating face 120, the invention is not limited in this regard. Seating face 120 is usually formed by applying an amount of cladding to a valve body and then grinding the cladding at a desired angle to form seating face 120. Whether the edge of the cladding layer aligns with the seating face depends on the shape of the cladding layer and the amount of cladding removed during grinding. While Figures 2-4 show protective coating 124 covering a portion of seating face 120, this is not necessary so long as cladding layer 120 extends far enough beyond seating face 120 such that protective coating 124 can overlap the interface by a desired amount (e.g., 0.005 inches).

The inlet valves of the present invention can be made from any metals suitable for use in an internal combustion engine. As described above, the cladding is a hard metal or metal alloy that gives the valve seat improved wear and resistance to corrosion and deformation. The cladding can have a single layer or more than one layer of hard corrosion resistant metals or metal alloys.

Examples of suitable materials for use as a cladding include nickel or cobalt alloys. In these alloys, the nickel or cobalt is typically the single greatest element by weight. Illustrative nickel based alloys include at least about 40 wt% Ni and at least one component from the group of cobalt, chromium, aluminum, tungsten, molybdenum, titanium, or iron. Examples of cobalt based alloys typically include at least about 30 wt% Co and at least one component from the group of nickel, chromium, aluminum, tungsten, molybdenum, titanium, or iron. Stellite is a well known cobalt-chromium alloy that is suitable for use as cladding in the present invention.

The valve head body 126 can be made of any metallic material, including softer metals that are normally susceptible to corrosion and/or substantial wear under the harsh conditions of an internal combustion engine. The metallic material, in contrast to the cladding, is a metal or metal alloy that is not readily used for its corrosion resistance, but has other beneficial properties such as low cost. In an exemplary embodiment, the valve head body is made from steel, preferably low- carbon steel. The valve stem 114 can be made from any of the metallic materials suitable for making the valve head 112 and can be the same or a different metal than the metal used to make valve head 112. In a preferred embodiment, valve stem 1 12 is made from steel, preferably low carbon steel. Valve head 112 and valve stem 114 can be an integral piece or joined together using known techniques (e.g., welding).

Figures 2—4 show a disk-like valve head 112 and an annular seating face 120. This shape is very typical of inlet valves used in many internal combustion engines and has the advantage of facilitating air flow. However, the present invention also includes inlet valves having shapes other the disk-like.

The protective coatings of the present invention can be any coating that can protect the metals of the valve body from corrosion and gas impingement. The protective coatings are typically selected to withstand temperatures and conditions within the air intake of the internal combustion engine. Because the air intake is adjacent the combustion chamber, the air intake can reach high temperatures (e.g., between about 300 °C to about 1000 °C. The protective coating is also selected to resist corrosion in the presence of recirculated exhaust gases and/or gas impingement from gases moving through the air intake. The protective coating can be any ceramic, metal, metal alloy, or combination thereof that can be bonded to the surface of the inlet valve and form a solid protective barrier to the underlying metal during normal engine operation. Those skilled in the art are familiar with the many different types of protective coatings that can be applied to metals to prevent corrosion and improve wear. Example novel compositions that can be used with the engine valves according to one embodiment of the present invention are described below.

In one embodiment of the invention, the inlet valves of the present invention can be coated using any known technique suitable for applying and bonding a metal and/or ceramic coating to a metal substrate. Examples of suitable methods include conventional spaying techniques, brushing, thermal spray techniques such as high- velocity oxy-fuel (HVOF), plasma spray techniques such as air plasma spray (APS), vacuum plasma spray (VPS), and low pressure plasma spray (LPPS), and vapor deposition techniques such as electron beam physical vapor deposition (EBPVD). The application of the protective coating to the inlet valve is controlled to ensure that the cladding-body interface is covered. Preferably the entire bell region of the valve head and a portion of the valve stem are coated with the protective coating. II. INTERNAL COMBUSTION ENGINES INCORPORATING COATED INLET VALVES

The present invention also includes internal combustion engines incorporating coated inlet valves such as inlet valve 100. As shown in Figure 4, an internal combustion engine 200 includes a combustion chamber 202, a piston 204, an exhaust valve 206, and an inlet valve 100 having a protective coating according to the present invention. Cams 208a and 208b selectively open and close exhaust valve 206 and inlet valve 100 respectively during engine operation.

Inlet valve 100 is configured to engage inlet seat 210 to seal the combustion chamber from air intake 212. Valve 100 is actuated via cam 208b to open and close inlet port 214. Valve 100 is guided in its motion through valve guide 216.

Air intake 212 allows fresh air to be drawn into combustion chamber 202 when inlet valve 100 is in the open position. Fresh air is mixed with fuel from fuel injector 216 and enters the combustion chamber 202 through inlet port 214. The path defined by the air intake 212 is the gas path. A portion of inlet valve 100 is positioned in the gas path. The portion of inlet valve 100 in the gas path is the area between the valve seat and the portion of the stem that is outside the valve guide 216. In a preferred embodiment, inlet valve 100 has a protective coating covering the portion of inlet valve 100 that is within the gas path. Engine 200 can be a gas engine a diesel engine, a flex fuel engine or any other type of engine that uses an inlet valve. Those skilled in the art will recognize that there are many different configurations of engines and engine types for which the inlet valves of the present invention will be advantageously incorporated.

In an exemplary embodiment, the engine 200 has an EGR system. The EGR system includes an EGR outlet 218 that receives exhaust gases when exhaust valve 206 is open during engine operation. In a typical EGR system exhaust gases are sampled using sensors and a central processing unit determines and/or monitors the amount of NO_x, SO_x, particulate, or other pollutant in the exhaust gases. The levels of pollutants in the exhaust gas can be reduced by recirculating exhaust gas back into the combustion chamber. The processor causes exhaust gases to be recirculated by opening EGR valve 220, which directs exhaust gases to EGR inlet 222. Recirculated exhaust gases entering EGR inlet 222 are mixed with the fresh air and drawn into combustion chamber 202. As the recirculated exhaust gases are drawn into combustion chamber 202, the recirculated exhaust gases impinge on the portion of inlet valve 101 that is exposed in inlet. Coating 124 on inlet valve 100 protects inlet valve 100 from high velocity and/or corrosive gases in the gas path during combustion. Protecting the cladding- body interface and/or the bell region and/or the exposed stem region of inlet valve 100 can be particularly advantageous when recycled exhaust gases are introduced into the combustion chamber 202 since these gases are more likely to be corrosive.

Protective coating 124 can also protect inlet valve during shut down of the engine. During shutdown, corrosive gases can condense and pool on inlet valve 100. Condensed recirculated exhaust gases can be particularly corrosive due to the NO_x and SO_x compounds in these gases. Protective coating 124 resists the corrosion of the condensed vapor, thereby protecting inlet valve 100. Consequently, the engines of the present invention are more durable than engines having valves that are not coated.

The engines of the present invention can be incorporated into any known machinery or device that utilizes an internal combustion engine employing an intake valve. For example, the engines of the present invention are suitable for use in automobiles, ships, airplanes, heavy construction equipment, electric generators, and the like. The engines of the present invention are more likely to last longer because of the durability of the valves. The durability of a valve in an internal combustion engine is particularly important since valve failure can be catastrophic to the engine. While some parts of an internal combustion engine can be simply replaced if they fail, the inlet valves will often cause irreparable damage to the engine if they fail. If an inlet valve fails, the broken parts can be sucked into the combustion chamber and are likely to damage the engine block and piston heads. Consequently engine life can be significantly shortened if the inlet valves fail. The durability of an internal combustion engine can also significantly and beneficially impact the value of an automobile, ship, generator, or other machinery incorporating coated valves of the present invention.

III. EXAMPLE COMPOSITIONS FOR COATING ENGINE VALVES

In one embodiment, the engine valves are coated with a coating that can be cured at relatively low temperatures and/or using infrared energy. In this embodiment, the protective coating compositions generally include the following three components: (i) a metal and/or a ceramic material, (ii) a binder, and (iii) a solvent.

A. Components Used to Make Ceramic Coatings

1. Metals and Ceramic Materials The coating compositions of the present invention include a metal oxide as a primary component and optionally metals as a secondary metallic component. In a preferred embodiment, the coatings include at least one metal oxide and at least one metal. The combination of metal oxides (i.e., ceramics) and metals can contribute to the high temperature and corrosion resistance of the cured coating and the high emissivity of the uncured coating compositions. In an exemplary embodiment, the metals and/or ceramics are provides as particulate. The particulate can be one or more sizes and can range in size from about 1 nm to about 1 mm.

A wide variety of ceramics and metals can be used in the protective coatings of the present invention. Suitable examples include silicon, zinc, zirconium, magnesium, manganese, chromium, titanium, iron, aluminum, noble metals, molybdenum, cobalt, nickel, tungsten oxides thereof, and combinations thereof. Examples of suitable oxides include silica, calamine, zirconia, magnesia, titania, alumina, ceria, scandia, yttria, among others.

2. Binders The binders used in the coating compositions of the present invention are typically organic or inorganic materials that can bind the metals or ceramics before or during sintering (i.e., curing). Examples of suitable organic binders such as ethylene copolymers, polyurethanes, polyethylene oxides, various acrylics, paraffin waxes, polystyrenes, polyethylenes, celluslosic materials, polysaccharides, starch, proteins, "agar," and other materials. Suitable inorganic binders include silicon based binders such as soda silicate, kairome clay, titanium based binders such as titania sol and other inorganic binders such as aluminum phosphate.

3. Solvents

Any solvent can be used to combine and/or deliver the metal and/or ceramic material so long as the solvent is compatible with the particular metals and/or ceramics and binders being used. Examples of suitable solvents include polar solvents such as water, methanol, and ethanol and non-polar organic solvents such as benzene and toluene. B. Manufacturing Coating Compositions

The protective coating compositions are typically designed to provide a coating that can withstand temperatures and conditions within a combustion chamber, air intake, or exhaust. In an exemplary embodiment the protective coating are stable and corrosion resistant to temperatures in a range from about 300 °C to about 1000

°C.

The coating compositions are made by selecting one or more metal oxides or metals, one or more binders, and one or more solvents and then mixing the components to form a paste or slurry. In an exemplary embodiment, the metal oxide is the predominant component. The metal oxide gives the protective coating heat resistance and resistance to corrosion. The metal oxide is typically included in an amount in a range from about 30 wt% to about 70 wt% of the coating composition (i.e., the uncured composition).

Metals can be included in the coating composition, typically in smaller amounts than the metal oxide. In a preferred embodiment, the amount of metal in the coating composition is in a range from about 0.5 wt% to about 20 wt%. The metals can give the coating toughness and heat resistance and help with the curing process.

The solvent is typically included in an amount that ranges from about 10 wt% to about 30 wt% of the coating composition. The solvent serves as a carrier or medium for mixing the metal oxides, metals, and binders. The consistency of the coating composition can be adjusted by adding greater or lesser amounts of solvent. If desired, the coating composition can be made into a slurry such that it can be applied by spray coating.

The metal oxides, metals, binders, and/or solvents can be selected to give the uncured coating composition high emissivity. Protective coating compositions that have high emissivity can be cured at relatively low temperatures using infrared radiation. The coating composition preferentially absorbs infrared energy, thus heating up, while low emissivity uncoated portions tend to reflect the infrared energy, thereby remaining cooler. In a preferred embodiment, the coating composition has an emissivity of greater than about 0.7, more preferably greater than about 0.9, and most preferably greater than about 0.95. The emissivity of a material can depend on the temperature. For purposes of the present invention, the emissivity value is based on the emissivity of the coating composition at the curing temperature. The emissivity of the coating composition will depend on all the components in the coating. Typically selection of the metal oxide has the most significant impact on the emissivity of the coating composition as a whole. Emissivity value for various suitable metal oxides is provided in Table 1.

Table 1

IV. METHODS OF COATING INLET VALVES

The methods for coating valves according to the present invention generally include (i) providing an inlet valve that has a valve stem, a valve seat, and a cladding- body interface (ii) masking the valve seat and at least a portion of the valve stem, (iii) applying a metal and/or ceramic protective coating to an unmasked portion of the valve so as to cover the cladding-body interface; and (iv) curing or sintering the protective coating. A. Preparing The Valve For Coating

Typically the engine valve is prepared in various ways before a coating composition can be applied. The surface of the engine valve is prepared to ensure good bonding between the valve and the coating. Preparing the surface typically includes cleaning and roughening the surface. In an exemplary embodiment, the surface is washed to remove lubricants and other materials that can affect bonding of the protective coating. Depending on the type of coating to be applied and the type and condition of the metal substrate, it can be advantageous to roughen the valve surface that is to be treated.

Figure 5 shows exemplary tooling 300 that can be used to mask the valve seat 116 and a portion of the valve stem 114 of valve 100. Masking the valve seat and valve stem ensures that the valve seat 116 and valve stem 114 are not damaged during the manufacturing process.

The valve seat 116 is masked using three plates. A bottom plate 302 provides a support for valve 100 and the remaining plates. Spacer plate 304 provides spacing between bottom plate 306 and a masking plate 306. The thickness of spacer plate 304 is selected such that the bottom edge 308 of masking plate 306 is positioned on seat face 108 so as to cover valve seat 116.

Spacer plate 304 and masking plate 306 are made by precision cutting an aperture in a sheet of metal. The aperture 310 in spacer plate 304 is precision cut to fit around the outside diameter of valve head 112. The aperture 312 in masking plate 306 is precision cut to fit against the seating face 120.

In one embodiment, the plates are designed to simultaneously mask a plurality of inlet valves. In this embodiment, a plurality of apertures are cut into spacer plate 304 and a plurality of apertures are cut into masking plate 306 such that a plurality of inlet valves can be prepared from a single set of plates. Due to the small tolerances typically needed to precisely mask the valve seat, a compressible layer 314 can be positioned between masking plate 306 and spacer plate 304. Compressible layer 314 can provide good contact between spacer plate 304 and masking plate 306 even if the aperture in masking seat 306 is slightly small thereby causing masking plate 306 to sit higher on seating face 120. Alternatively, if spacer plate 304 is slightly too thin, compressible layer 314 can provide the additional spacing to properly position masking plate 306 on seating face 120. A plurality of clamps or similar devices can be used to compress the plates. Clamping the plates can be beneficial because it provides a tight seal to prevent grit or particulate from contacting the valve seat during grit blasting or another technique used to roughen the surface.

The valve stem 114 is partially masked using a sleeve 316. Sleeve 316 is closed at one end and the length of sleeve 316 is selected such that the sleeve ends along valve stem 114 where the protective coating is to be applied. Sleeve 316 is preferably made from a soft metal such as aluminum to prevent the sleeve from scratching valve stem 114 as sleeve 316 is put on and taken off. If a soft metal is used to make sleeve 316, sleeve 316 can be coated with a layer 318 of silicon or other coating that can protect sleeve 316 against grit blasting. Coating sleeve 316 with silicon or other resilient coating can extend the life of the sleeve such that it can be reused.

Once tooling 300 is positioned on valve 100, valve 100 is grit blasted using blasting tool 320 to roughen the surface of the unmasked portion. Equipment used to grit blast (/. e. , sand blast) metals is known in the art. An example of a suitable grit is aluminum oxide. The grit size is typically in a range from about 80 grit to about 300 grit. Grit blasting is carried out for sufficient time to roughen the surface with minimal removal of material. Once grit blasting is complete, tooling 300 can be removed and valve 100 can be sprayed clean with air. Grit blasting results in a roughened area 119 (Figure 5). B. Applying The Coating To An Engine Valve

Figure 6 illustrates exemplary masking tooling 400 that can be used to mask valve 100 for purposes of applying the protective coating to the roughened area 1 19 of valve 100. Masking tooling can be a single ring having an aperture therethrough for receiving valve head 102. Masking tooling 400 has a first aperture 402 with a width that is slightly larger than the width of valve head 1 12 such that masking tooling 400 can be slidably received over valve head 112. A second aperture 404 is sized and configured to engage the seat face 120 so as to leave the roughened area 1 19 exposed. An edge 406 of masking tooling 400 engages the seating face 120 on the cladding so as to leave the cladding interface 130 exposed while covering the valve seat 116. A portion of valve stem 114 is masked using sleeve 316. The length of sleeve

316 is selected to match the grit blasting masking, thereby leaving roughened area 119 exposed. Sleeve 316 is preferably made from a soft metal such as aluminum to avoid damaging valve stem 114.

Once tooling 400 and sleeve 316 are in place, a protective coating composition is applied to the roughened area 119. In a preferred embodiment, the uncured coating is sprayed onto roughened area 119 using spray nozzle 408. In an exemplary embodiment a single thin coating of material is applied by rotating inlet valve 400. The coating can be any desired thickness so long as the thickness does not substantially interfere with valve movement or gas flow over the valve. In a preferred embodiment, the coating thickness is in a range from about 0.0002 inches to about 0.002 inches. The desired thickness depends on the type of coating used and the amount of material needed to provide the desired protection. Relatively thin coatings are preferred due to the decreased cost and the increased simplicity with which they can be applied.

Sleeve 316 and tooling 400 can be coated with a non-stick coating to hinder the bonding or adhesion of the protective coating composition to the tooling and sleeve. Examples of suitable non-stick coatings include polyfluorocarbons.

Preventing the protective coating from adhering to the tooling and/or sleeve allows these parts to be reused for coating additional parts.

The method of the present invention provides an economic and rapid method for coating a valve with a protective coating. The protective coating of the present invention is advantageously applied over the cladding interface to prevent corrosion at the cladding interface. The tooling 300 and masking tooling 400 can be designed and machined to ensure that the cladding interface is covered with the protective coating.

While Figures 5 and 6 show masking for preparing and coating the cladding- body interface and the bell region of the valve, the present invention can also be used to coat other areas of a valve. For example, the present invention can be used to coat the portion of the valve that is within the combustion chamber during combustion. Protective coatings in this area of the valve can protect the valve from the wear and tear caused by combustion.

The coating can be applied using any known technique such as spray coating or brushing. Typically the amount of solvent in the coating composition is adjusted to facilitate the type of coating that is desired. For example, in a preferred embodiment the coating composition is a slurry such that the coating can be sprayed onto a valve. The thickness of the valve can be determined by controlling the rate of spraying and the duration of spraying. The high emissivity coatings can be cured using infrared radiation to heat the coating to a temperature in a range from about 100 °C to about 650 °C, more preferably in a range from about 200 °C to about 550 °C, and most preferably in a range from about 250 ⁰C to about 450 ⁰C. Curing the protective coatings using infrared radiation can be advantageous because the coating can be cured rapidly with good uniformity. In addition, the relatively low temperatures needed to cure the high emissivity coatings minimizes the energy costs associated with curing, thereby improving the cost effectiveness of the process. V. HIGH THROUGHPUT COATING AND CURING SYSTEM

Figure 7 shows an exemplary system 500 according to the present invention. System 500 generally includes a movable track 502 that passes through an infrared oven 504. A plurality of attachment apparatus (collectively referred to as apparatus 506) are connected to movable track 502. Each of the attachment apparatus is configured to hold an engine valve (not shown) that is transported through system 500 on movable track 502. System 500 can also includes a pre-heating oven 508 for preheating engine valves before they are coated with the coating composition. System 500 also includes a spraying region 510 where engine valves are spay coated using a spraying device 512. Along a portion of track 502 is a region 514 for placing uncoated engine valves on movable track 502 and another region 516 for removing engine valves that have been coated by system 500. Control panel 518 can be included to electronically control one or more components of system 500 (e.g., infrared oven 504 and track 502).

A. Movable Track The movable track 502 can be made from any type of material and have any configuration so long as it can withstand the temperatures to which it will be exposed to in the oven and so long as the movable track 502 can securely transport the attachment apparatus and engine valves through system 500. In an exemplary embodiment, movable track 502 includes a plurality of apertures where attachment apparatus 506 can be slidably received. Movable track 502 is typically powered by an electric motor (not shown) using known mechanisms.

B. Attachment Apparatus

The attachment apparatus are configured to removably hold an engine valve. The attachment apparatus can have any shape so long as the engine valves can be positioned thereon and subsequently removed without damaging the engine valve. The attachment apparatus 506 can also be made from any material so long as the material can withstand the temperatures to which it will be exposed in the infrared oven. In an exemplary embodiment the attachment apparatus comprises steel. Figure 8A illustrates one exemplary embodiment of an attachment apparatus 600 having a configuration suitable for removably holding a typical engine valve. Attachment apparatus 600 includes a body of material 602 that has an upper surface 604 that is configured to receive an engine valve. In an exemplary embodiment, upper surface 604 is substantially circular on the sides and planer on the upper surface. This configuration is particularly suitable for receiving the bell end of a typical engine valve such as those described below with reference to Figures 9.

The attachment apparatus 600 can also include a gear 608 attached to a stem 210. Gear 208 can be used to cause rotation of apparatus 600 and thus rotation of an engine valve attached thereto. Stem 610 can be made cylindrical such that it can rotate within an aperture of movable track 502. As shown in Figure 8B, gear 608 is configured to engage a stationary gear 612 positioned adjacent to movable track 614. The stationary gear 612 can be positioned at only those locations around the movable track where it is desired that the engine valve spin, such as in infrared oven 504, in spraying region 510, and/or within preheating oven 508 (Figure 7). The spinning motion of the engine valves can facilitate even heating, spraying, and/or curing. The rate at which apparatus 600 rotates will depend on the rate at which movable track 614 is moving and the gear size of gear 608. While the foregoing mechanism provides a simple and economical mechanism for causing rotation of the attachment apparatus and engine valves, the present invention is not limited to this particular mechanism; other mechanism can be used to cause rotation of the attachment apparatus of the present invention.

In a preferred embodiment, a portion of the attachment apparatus is made from a magnetic material to removably hold the engine valves thereto. As shown in Figure 8A, attachment apparatus 600 includes a magnetic portion 606 that forms part of upper surface 604. The magnetic material advantageously holds a steel engine valve on apparatus 600. Removably holding engine valve on apparatus 600 using a magnet is particularly advantageous because the engine valves can be placed and removed very quickly and because this attachment mechanism is unlikely to cause scratches or other damage to the engine valve. Furthermore, the engine valves can be quickly loaded and/or unloaded from the attachment apparatus either through an automated process or manually. C. Attachment Apparatus and Engine Valve Assembly

System 500 can be used to efficiently and economically coat a portion of an engine valve with a protective coating. The attachment apparatus, engine valve, and masking tooling can form an assembly. 1. Assembly

Figure 9 illustrates an attachment apparatus and engine valve assembly 650 according to one embodiment of the present invention. The bell end of engine valve 700 is disposed on the upper surface 604 of attachment apparatus 600. Magnetic portion 606 of attachment apparatus 600 exerts an attractive force on valve head 702 to removably hold engine valve 600 on attachment apparatus 600.

A masking tooling 616 is slidably placed over a portion of valve head 702. Masking tooling 616 can be a single ring having an aperture therethrough for receiving valve head 502. Masking tooling 616 has a first aperture with a width that is slightly larger than the width of valve head 702 and attachment apparatus 600 such that masking tooling 616 can be slidably received over valve head 702 and attachment apparatus 600. A second aperture is sized and configured to engage the seat face 708 so as to leave the portion 718 of engine valve 700 exposed. Masking tooling 616 engages the seating face 708 on the cladding so as to leave the cladding interface 716 exposed while covering the valve seat. This allows the coating to cover cladding interface 716 and extend slightly over a portion of the seating face 708, which minimizes corrosion and breakage in this region. The portion of engine valve 700 covered by masking tooling 616 is protected from the coating process of system 500.

Assembly 650 can also include a sleeve 618 that partially masks stem 704. Sleeve 618 is closed at one end and the length of sleeve 618 is selected such that the sleeve ends along valve stem 704 where the protective coating is to be applied. Sleeve 618 is preferably made from a soft metal such as aluminum to prevent the sleeve from scratching valve stem 704 as sleeve 618 is placed over and removed from stem 704.

Sleeve 618 and masking tooling 616 can be coated with a non-stick coating to hinder the bonding or adhesion of the protective coating composition to the tooling and sleeve. Examples of suitable non-stick coatings include polyfluorocarbons. Preventing the protective coating from adhering to the tooling and/or sleeve allows these parts to be reused many times for coating additional parts. While the attachment apparatus in Figures 8A-8B, and Figure 9 show an attachment apparatus and masking suitable for coating the "bell region" of an engine valve, the present invention also extends to attachment apparatus and masking for coating other areas of a valve. For example, the present invention can be used to coat the portion of the valve that is within the combustion chamber during combustion (i.e. the bell end 720). Protective coatings in this area of the valve can protect the valve from the wear and tear caused by combustion. An attachment apparatus for coating this portion of the engine valve is typically configured to receive the valve stem and has masking to block coating of the valve seat, for example. Typically the engine valve is prepared in various ways before it is used in system 100 of the present invention. For example, the portion of the surface of the engine valve to be coated can be prepared to ensure good bonding between the valve and the coating. Preparing the surface typically includes cleaning and roughening the surface. In an exemplary embodiment, the surface is washed to remove lubricants and other materials that can affect bonding of the protective coating. Depending on the type of coating to be applied and the type and condition of the metal substrate, it can be advantageous to roughen the valve surface that is to be treated (e.g. by sand blasting).

D. Preheating Oven With reference again to Figure 7, system 500 can optionally include a preheating oven 508. The preheating oven can be any type of oven suitable for warming the engine valves. Preheating the engine valves helps prevent the coating composition from running or pooling, thereby ensuring a more even coating on the engine valve (e.g., by driving off a portion of the solvent by evaporation). In a preferred embodiment, the preheating oven 508 is an infrared oven having infrared lamps 520. Using an infrared preheating oven to heat the engine valves can be advantageous because the heating can be rapid. In a preferred embodiment, the attachment apparatus is configured to cause the engine valves to spin as they travel through the preheating oven so as to more evenly heat the engine valves. E. Spraying Device and Coating Compositions

A spraying device 512 is used to apply a coating composition to the valves. The coating composition is typically stored in a reservoir that is in fluid communication with the spraying device 512. The spraying device 512 delivers the coating composition to at least a portion of the surface of the engine valve via a spray nozzle and/or a brush. If desired, the composition can be maintained under pressure, and the flow of coating composition can be manipulated by controlling the pressure and/or the size of the nozzle on the spraying device. The constituents in the coating composition can also affect the flow rate of the coating composition through the spraying device 512. For example the amount and type of solvents can affect the flowability of the coating composition. Thus the pressure and nozzle size will typically need to be selected according to the particular coating composition, and desired coating thickness. The spraying device 512 can be hand operated by a person or automated using a robot and a computerized controller.

In a preferred embodiment, the engine valves are caused to spin as they travel through spraying region 510. The rotation of the engine valves can assist in applying a uniform protective coating to the engine valves. In an exemplary embodiment a single thin coating of material is applied to each engine valve moving through region 510.

The coating can be any desired thickness so long as the thickness does not substantially interfere with valve movement or gas flow over the valve when the engine valve is used in an internal combustion engine. In a preferred embodiment, the coating thickness is in a range from about 0.0002 inch to about 0.002 inch. The desired thickness depends on the type of coating used and the amount of material needed to provide the desired protection. Relatively thin coatings are preferred due to the decreased cost and the increased simplicity with which the coating can be applied.

The coating compositions used in the system of the present invention are selected or manufactured to be curable in an infrared oven. In addition, the cured coatings are resistant to high temperatures such that the coating can withstand the extreme conditions of an internal combustion engine. In an exemplary embodiment the protective coating are stable and corrosion resistant to temperatures in a range from about 300 °C to about 1000 ⁰C.

F. Infrared Ovens And Curing The Coating Composition Once the coating composition has been applied to the desired portion of the valve, the valves are transported through infrared oven 504 where infrared radiation cures the coating composition. The high emissivity of the coating compositions allows efficient absorption of the infrared energy and results in quick and rapid curing. Infrared oven 504 can have any number of infrared lamps 522. In a preferred embodiment, the infrared lamps 522 are angled to apply direct radiation to the surface of the coating composition. In an exemplary embodiment, the engine valves are caused to rotate as the engine valves travel through the infrared oven 504 such that the valves are heated more uniformly.

To cause curing, the coating compositions are exposed to the infrared radiation so as to heat the coating composition to a temperature in a range from about 100 ⁰C to about 650 °C, more preferably in a range from about 200 °C to about 550 ⁰C, and most preferably in a range from about 250 ⁰C to about 450 ⁰C. In a preferred embodiment, the coating cures in less than about 0.5 hour, more preferably less than about 20 minutes, and most preferably in less than about 5 minutes. The ability to cure relatively quickly and/or at relatively low temperatures can dramatically reduce the energy requirements for applying the coating.

Any source of infrared radiation can be used so long as the intensity is sufficient to raise the temperature of the coating to the desired curing temperature. Suitable sources of infrared radiation include gas or electric powered infrared lamps. Electric powered lamps are typically preferred for their ability to reach hotter temperatures and/or better control of the temperature. Gas fired IR lamps are typically preferred for their lower cost of operation. Curing the protective coatings using infrared radiation can be advantageous because the coating can be cured rapidly with good uniformity. In addition, the relatively low temperatures needed to cure the high emissivity coatings minimizes the energy costs associated with curing, thereby improving the cost effectiveness of the process G. Automation

Control panel 518, shown in Figure 7, can be used to provide automation to the system. Control panel 518 typically includes microprocessors and/or other circuitry that can monitor and/or control the performance of one or more components of system 500. In an exemplary embodiment, control panel 518 controls the rate of travel for movable track 502 and/or the intensity and/or duration of the emission of infrared radiation from preheating oven 508 and/or infrared oven 504. The control panel 518 facilitates automation to reduce costs and increase output. The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims

CLAIMSWhat is claimed is:

1. An inlet valve for use in an internal combustion engine, comprising: a valve stem; a valve head connected to the valve stem, the valve head comprising, a valve head body comprising a metallic material; a hard cladding material covering a portion of the valve head body, at least a portion of the surface of the cladding forming a valve seat; and wherein the cladding and the metallic material abut one another, thereby forming a cladding-body interface; and a protective coating bonded to the valve head and overlapping the cladding-body interface.

2. An inlet valve as in claim 1, wherein the protective coating covers substantially the entire bell region.

3. An inlet valve as in claim 1, wherein a first edge of the protective coating begins on the cladding at least about 5 thousands of an inch away from the cladding-body interface.

4. An inlet valve as in claim 13, wherein a first edge of the protective coating begins on the cladding at least about 15 thousands of an inch away from the cladding-body interface.

5. An inlet valve as in claim 13, wherein a first edge of the protective coating begins on the cladding at least about 30 thousands of an inch away from the cladding-body interface.

6. An inlet valve as in claim 1, wherein the cladding comprises a metal alloy that is harder than the metallic material of the valve head body.

7. An inlet valve as in claim 6, wherein the cladding comprises a cobalt- chromium alloy.

8. An inlet valve as in claim 1, wherein the metallic material comprises steel.

9. An inlet valve as in claim 1, wherein the thickness of the coating is in a range from about 0.0002 inches to about 0.002 inches.

10. An inlet valve as in claim 1, wherein the coating continuously covers the cladding-body interface.

11. An internal combustion engine comprising an inlet valve as defined in claim 1.

12. A method for applying a protective coating to a valve of an internal combustion engine, comprising: providing a valve suitable for use in an internal combustion engine; optionally masking a portion of the valve; providing a protective coating composition having an emissivity greater than about 0.7, the protective coating composition comprising, one or more metal and/or ceramic materials; one or more organic and/or inorganic binders; and one or more solvents; coating at least a portion of the surface of the valve with the protective coating composition; and at least partially curing the protective coating composition by heating the coating to a temperature in a range from about 100 ⁰C to about 650 °C using infrared radiation.

13. A method as in claim 12, wherein the emissivity value of the protective coating is at least about 0.9.

14. A method as in claim 12, wherein the emissivity value of the protective coating is at least about 0.95.

15. A method as in claim 12, wherein the protective coating is at least partially cured at a temperature in a range from about 200 °C to about 550 ⁰C.

16. A method as in claim 12, wherein the protective coating is at least partially cured at a temperature in a range from about 250 °C to about 450 ⁰C.

17. A method as in claim 12, wherein the portion of the surface of the valve that is coated is grit blasted prior to applying the coating composition thereto.

18. A method as in claim 12, wherein the portion of the surface of the valve that is coated is heated prior to applying the coating composition thereto.

19. A method as in claim 12, wherein the protective coating composition is applied as a slurry.

20. A method as in claim 19, wherein the slurry is aqueous and comprises water as a solvent.

21. A method as in claim 12, wherein the protective coating comprises at least one type of ceramic material.

22. A method as in claim 12, wherein the protective coating comprises at least one type of metal material.

23. A method as in claim 12, wherein the protective coating comprises both a ceramic material and a metal material.

24. A method as in claim 12, wherein the protective coating comprises at least one type of organic binder.

25. A method as in claim 12, wherein the protective coating comprises at least one type of inorganic binder.

26. A method as in claim 12, wherein the protective coating comprises both an organic binder and an inorganic binder.

27. A method as in claim 12, wherein the protective coating is cured in less than about 0.5 hour.

28. A method as in claim 12, wherein the protective coating is cured in less than about 20 minutes.

29. A method as in claim 12, wherein the protective coating is cured in less than about 5 minutes.

30. A system for coating an engine valve, comprising: an infrared oven comprising at least one infrared lamp; a movable track forming a loop, a portion of the track being disposed within the infrared oven; a plurality of attachment apparatus connected to the movable track and configured to receive and hold an engine valve on the track as the track moves; and a spraying device configured to apply a coating composition to the plurality of engine valves disposed on the plurality of attachment apparatus, the spraying device being disposed along the movable track before the infrared oven.

31. A system as in claim 30, in which the energy output of the infrared oven is set so as to heat a coating within the oven to a temperature in a range from about 100 °C to about 650 °C.

32. A system as in claim 30, in which the energy output of the infrared oven is set so as to heat a coating within the oven to a temperature in a range from about 200 °C to about 550 °C.

33. A system as in claim 30, further comprising a preheater positioned along the movable track before the spraying device, such that engine valves being held on the movable track will be heated prior to being coated by the spraying device.

34. A system as in claim 30, further comprising a reservoir of coating composition in fluid communication with the spraying device, the coating composition comprising an aqueous slurry.

35. A system as in claim 30, further comprising an electronic control system that allows a user to input the desired speed of the movable track and controls the speed of the movable track based on the user input.

36. A system as in claim 35, in which the electronic control panel simultaneously controls the speed of the movable track and the temperature of the infrared oven, thereby controlling the drying time of engine valves within the infrared oven.

37. A system as in claim 36, in which the drying time is less than 30 minutes.

38. A system as in claim 36, in which the drying time is less than 5 minutes.

39. A system as in claim 30, in which the plurality of attachment apparatus are configured to rotate about a vertical access when the plurality of attachment apparatus are moving through at least a portion of the infrared oven.