DE2100237A1 - Tungsten alloy and process for its manufacture - Google Patents

Description

Manchester and Weidmen Roads
Manchester, Missouri / V.St.A ,

Our reference: R 761

Tungsten alloy and process for its manufacture

The invention relates to a tungsten alloy used for Production of hard coverings or coatings for a wide variety of substrate materials including such based on iron and steel is suitable Alloy is particularly suitable as a coating for piston rings including the sealing and oil control ring © for pistons of internal combustion engines.

Piston rings, sealing rings and ülabatreifrings are usually provided with a hard metal coating. A typical example of this is a hard molybdenum coating material applied by a flame spraying process, as high temperatures occur during operation of piston rings in highly compressed internal combustion engines *. Another coating for piston rings

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exists ζ. B, made of a refractory metal carbide such as Tungsten carbide. It was previously assumed that in the event that tungsten made up the majority of the alloy coating forms, the tungsten in the form of a compound, for example as tungsten carbide, must be present. Try one Producing a piston coating that contains tungsten itself as a separate phase has not led to success, because the tungsten has proven to be too soft and the piston ring not under typical operating conditions protected to the extent desired.

It would therefore be regarded as a significant technical advance if it were possible to specify an alloy which contains a substantial amount of tungsten as a separate phase yet is sufficiently hard to be used as a coating for piston rings in high-compression internal combustion engines to be able to.

The present invention now provides such a metal alloy, which is suitable for the production of hard coatings and which consists of an alloy matrix which a separate tungsten phase hardened interstitially with boron contains. The alloy matrix is preferably a nickel-chromium or nickel-aluminum matrix.

The above alloy, which is particularly suitable as a coating for piston rings, is preferably after a Plasma jet spraying process produced. The hard tungsten alloy of the invention is generally made by one converts tungsten carbide into tungsten in an oxidizing flame of a plasma arc torch and then the Tungsten combined with boron to harden the tungsten phase.

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In the usual plasma jet spraying process, a plasma flame spray gun, which has a spray chamber, is used into which the plasma gas is introduced. To ionize the gas, an electric is used in the chamber Arc generated. A spray nozzle, which is preferably a spray metal powder, is attached to the chamber is supplied in the form of a suspension in a carrier gas. The metal powder is then melted and processed as a Workpiece-acting base material pressed on, whereby the base material is coated. The coating on the base material is generated by having the spray gun opposite the workpiece or the workpiece opposite the Spray gun or both moved against each other in order to deposit several thin metal layers one after the other.

The improvement of the method described above, which constitutes the essence of the method according to the invention, consists now that you have a powder of tungsten carbide, boron and at least one:; ·! another alloying element is used. Hydrogen in conjunction with nitrogen or argon is used as the plasma gas. The hydrogen is with a flow velocity of 0.566 to 0.850 m (20 to 30 ft.) Hydrogen under standard conditions fed per hour. Another important variable that needs to be adjusted is the spacing of the tip gun of the workpiece. This can be varied from 8.9 to 16.5 cm (3.5 to 6.5 inches). Under these conditions will the base material is provided with a hard coating consisting of the alloy described above, which is a hardened one Contains tungsten phase.

The aim of the invention is therefore to provide a new alloy, in particular to specify a metal alloy containing a separate hard tungsten phase which is used to produce a hard

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Coating can be used on the running surface of a piston ring, which consists of a plasma jet fuel zverfahr en applied refractory alloy. This hard coating is in place on the piston ring situ generated from a tungsten-containing powder with the help of a plasma jet spraying process.

The aim of the invention is also to provide a method for producing such a tungsten alloy, which as hard coat using a plasma jet deposition process in which certain variables of the process can be adjusted in a very special way so that the desired hard tungsten metal alloy coating is achieved.

Other features of the invention and advantages achieved in accordance with the invention will become apparent from the following description of particular ones preferred embodiments of the invention in conjunction with the accompanying drawings. However, be on it it should be noted that these particular embodiments are altered and modified in many ways can without departing from the scope of the present invention.

In the accompanying drawings mean

1 is a photomicrograph of a typical sample of a tungsten alloy according to the invention;

Figures 2 through 8 fluorescence x-ray photomicrographs of various components contained in a typical alloy according to the invention;

Figure 9 is a side elevation, partly in section, of one Piston ring cylinder arrangement of an engine, in which the piston has ring grooves which are provided with sealing rings and oil control rings

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are provided, each one of which is attached to the cylinder Has adjacent running surface, which is made of in situ, applied by a plasma jet spraying process consists of tungsten alloys according to the invention; Fig. 10 is an enlarged partial cross section through the upper part of the sealing ring in the piston of Fig. 9;

Figure 11 is a view similar to Figure 10 but illustrating the second sealing ring in the piston of Figure 9; Fig..12 is a view similar to Fig. 10, _m, but illustrating the oil scraper ring in the annular groove of the third ™

Piston of Fig. 9 »

Fig. 1J is a view similar to Fig. 10 but illustrates the oil control ring in the fourth bing groove of the piston of Fig. 9; ■ · ■

Figure 14 depicts a schematic cross-section through a plasma flame spray gun such as is typically used used to coat a base material according to the method of the invention; and

Fig. 15 shows a further schematic cross section by a plasma flame spray gun, which shows its operation in more detail.

As stated above, a new tungsten metal alloy was made found · This alloy, which is particularly suitable as a hard coating for piston rings, consists of a Iiegierungsmatrix, which has a separate, interstitial with Contains boron hardened tungsten phase. This alloy is the first alloy to contain a tungsten phase, the one has sufficient hardness that a hard coating can be made therefrom. This alloy has, for example a Vickers-Harte 40 DPN (DPN = »diamond penetration number at a load of 40 g) of more than about 2000. The hardness of the tungsten phase is generally between

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2500 and 5500, more often within the 2700 range to 3200 Vickers · The alloys of the present invention contain a relatively large amount of tungsten as separate Phase · The amount of tungsten is generally at least 35 volume- $ 6 of the alloy sample and is more often within the range of about 35 to about 60 volume ^

In a particularly preferred embodiment, the matrix containing the tungsten phase is a nickel-chromium matrix. This usually contains free nickel in this case. If free nickel is present, it is usually present in an amount of less than about 6.0 % .

The hardness of the nickel-chromium matrix phase is usually at least 800 Vickers (40 DPN), more often 850 to 1600 Vickers and more preferably 900 to 1200 Vickers · The free nickel phase, normally considered to be proportionate considered soft has a hardness of at least 400 Vickers (40 DPN). The free nickel hardness is usually within the range of about 400 to about 900 Vickers. In a preferred case, the free nickel hardness is 500 Vickers

Boron is of course an integral part of the invention Metal alloys, and it is usually in an amount within the range of about 1 to about 7, more commonly from 1.5 to 5% by weight, based on the weight of the Coating alloy, before. The boron hardens not only the tungsten phase, but also the free nickel phase · the interstitial one Hardening by boron takes place by expanding the lattice structures of tungsten and nickel. That is, the boron

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replaces tungsten in the lattice parameter, thereby hardening the tungsten phase sufficiently that it can be used as hard coating is usable.

As will be described in more detail below, the inventive Alloy preferably produced by plasma jet spraying of at least one of tungsten carbide and Boron and at least one further alloying element containing powder mixture or alloy. A typical one Tungsten carbide powder that can be sprayed from the following components:

25 to 55 wt% tungsten carbide

4 to 8 "cobalt

25 to 4-5 "nickel

3 to 7 ^M chrome

0.5 to 7 ⁿ aluminum

1 to ~ 7 "boron remainder essentially iron

A special alloy contains the following components:

40 Weight Il > Tungsten Carbide 6th It cobalt 38 ,8th • I nickel 6th Il chrome 1 Il boron 0 , 7 aluminum

The remainder is iron with small impurities of silicon and carbon.

In addition to the above-mentioned metals tungsten, nickel, chromium, aluminum, boron, cobalt and silicon, the inventive Also a number of other metals and alloys

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Contain metalloids, for example titanium, tantalum, niobium, vanadium, zirconium, hafnium, etc.

The alloys described above can also be used to produce coatings on a wide variety of conventional Surfaces, for example on iron and steel alloys, can be used for any purpose in which a surface that is resistant to wear and / or stress is required. For example, they are out The coatings produced with the alloys described here are extremely valuable as running surfaces for, for example Drills that are exposed to high loads. The coatings according to the invention can also be used for production of polished rod liners, plunger pistons (Plunger), from medium to high temperature resistant steel roller bearings, furnace rollers, motor valve trim, Glass molds, engine piston tops, and tempering rolls or the like can be used.

As already indicated above, the Alloys particularly suitable for coating the running surfaces of piston rings. The piston rings are preferred using a plasma jet spray process, such as as described below, coated in situ with the alloys of the invention.

When used to coat piston rings, the coating generally has a thickness within the range from about 0.051 to about 0.203 mm and in some cases the thickness of the coating is up to 0.305 mm. A special one The preferred method for coating the base materials is the use of a spraying process, which is preferably carried out with a plasma flame spray gun, for example of the type in which

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by constricting an electric arc in a nozzle with a gas forming the plasma, e.g. B, Nitrogen or argon alone as the primary gas or mixed with hydrogen as the secondary gas, a plasma flame is produced. Spray guns that generate a plasma flame in this way are for example in the U.S. Patent 2,960,594. In this procedure a powder is sprayed on, which ultimately forms the layer coating. The term used here "Powder" generally includes not only a powder in a loose form but also a powder in a bound form Shape. In the latter case, of course, a flame with one in the spray gun must be sufficient to melt the metal high temperature * A plasma flame is extremely suitable for this purpose.

The method of coating objects using a plasma jet spraying method is detailed by introducing a plasma gas into the spray chamber of a plasma flame spray gun. In this chamber an electric arc is created to ionize the gas and into one communicating with the chamber A spray metal powder, which is preferably suspended in a carrier gas, is introduced into the spray nozzle. That Metal powder is then melted and applied to a base material that serves as a workpiece, creating that base material is covered. The coating is made in detail by facing the spray gun moved the workpiece and the workpiece opposite the spray gun in order to deposit several thin layers of metal on it.

It has now been found that the method described generally above is carried out in a special way.

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Should be guided to by using a tungsten carbide powder or a tungsten alloy as the spray metal source to incorporate a tungsten phase in the coating.

The plasma flame must be oxidizing. Be a flame about 5 »^ cm (2 inches) from the nozzle of the spray gun and preferably containing about 80% air by suction. The high air content and high temperature of the plasma flame are required to oxidize the tungsten carbide particles and reduce them to tungsten according to the following equation:

WC + O ₂ > CO ₂ + W + W ₂ C

The W ₂ C can be present in very small amounts. The particle velocity at the stated gas flow rates and the stated spray gun-to-workpiece distance ^ is also very high, on the order of 122 m (400 feet) per second. The high speed of the molten alloy provides very high quench rates when the molten alloy strikes the cooler surface to be coated. Quench rates on the order of 0.5 x 10- * ⁰ C (10 * ⁰ F) per second have been found. Due to the high quenching speeds (spray cooling), the normally softer nickel-aluminum or nickel-chromium alloy matrix hardens in the finished coating.

If the following instructions are not followed as directed, there is a greater chance that a Tungsten carbide phase instead of a pure tungsten metal phase is formed.

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The improvement over a conventional plasma jet spraying process is that first tungsten carbide in the form of a powder (powder in its general definition) and boron and at least one other alloying element, for example one or more of the metals cobalt, nickel, chromium, aluminum, etc. are used . Hydrogen is used as the secondary gas in conjunction with nitrogen or argon as the primary gas to produce a plasma gas. It is essential that the hydrogen gas supply be at a fairly specific rate, namely at a flow rate of 0.566 to 0.850 m ^. (20 to 30 ft. ⁵ ), more often from 0.651 to 0.765 m ⁵ (23 to 2 ft. ⁵ ) below Standard conditions per hour. It has also been found that the distance of the spray gun from the workpiece is essential to achieve the desired tungsten phase. In particular, the distance can be varied between about 8.9 and about 16.5 cm (3 »5 to 6.5 inches). On an average test, the distance of the spray gun from the workpiece is about 10.1 cm (4 inches) or about 15.3 cm (6 inches). Under these conditions, the base material is provided with a hard tungsten coating, in particular with a tungsten phase hardened interstitially with boron.

It has been found that in order to achieve the best alloy coating desired and particularly for intercalation A number of other process variables are important to the desired tungsten phase in the alloy. For example, the velocity of the vertical passage, which determines the velocity of the gas, is that moves across the workpiece is important. It is most desirable to be the temperature of the spray material and that of the substrate to match and that

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is best achieved by moving the spray gun in a suitable manner relative to the workpiece The speed required for best results is generally from about 71 »1 to about 81.3 cm. (28 to 32 inches) per minute.

The angle between the spray gun and the workpiece is another important process variable. This angle should normally be within the range of about 35 to about 55 degrees when spraying seal rings. In the case of oil control rings (oil retention rings), this angle is O ⁰ , ie the coating is sprayed on at right angles (directly).

Another preferred means of performing the plasma spray process is to use a direct current having an amperage on the order of about 475 to about 550 amps to create the arc.A typical powder feed rate is within the range of about 4.54 to about 5 * 4 -4 kg (10 to 12 pounds) per hour. Ultimately, the flow rate of nitrogen or argon as the primary gas should be within the range of about 2.27 to about 2.69 m (80 to 95 ft.) Under standard conditions per hour, more usually 2.41 to 2.55 m ⁵ (85 to 90 ft. ⁵ ) per hour under standard conditions. In general, the powder is introduced using a carrier gas such as e.g. B. nitrogen, introduced into the nozzle. The carrier gas flow rate can be 1.27 to 1.70 nr (45 to 60 ft. ⁵ ) per hour under standard conditions, and more often it is 1.42 to 1.56 m ⁵ (50 to 55 ft. ⁵ ) under standard conditions per hour·

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The thickness of the deposited layer can be chosen freely and it depends of course on how often the Spray gun sweeps over the base material to be coated. In a typical case where a Piston ring is coated, this is done four times. In general, one layer is created with each spray 0.051 mm (0.002 inch) thick.

It should be noted that when the plasma jet spraying process is varied outside the limits given above, in many cases a tungsten carbide alloy arises that does not contain any free tungsten phase. The above The guidelines given must be strictly followed to ensure that the desired tungsten itself is considered separate phase containing alloy is obtained.

To better explain the alloys according to the invention and their production are described in more detail below the figures of the accompanying drawings.

Figure 1 is a photomicrograph showing the various phases obtained using an electron microprobe using the sample current images. In particular, a coating is shown which contains a free tungsten metal phase 1, a nickel-chromium matrix phase 2, free kick metal 3 and aluminum oxide 4 as main components. The sample was prepared by coating a piston ring using the plasma jet spray method described above, then a cross section of the coated piston ring was used for electron microscopy. The samples produced by the micro-examination were rough and were therefore only surface-polished using a biosafety agent in order to avoid the risk of damage. introduction

ORIGiMALINE PEOTiO

i 108-f 30 / Ί26 7

'"I:.' V

to avoid aluminum or chrome in the upper cable. The magnification in this study was 1100 times.

It was found that the tungsten phase of FIG was practically free of carbon, as evidenced by the X-ray fluorescence photomicrograph of the carbon distribution was shown. Although it could not be fully confirmed, it is believed that the tungsten carbide in the Spray powder is oxidized during spraying with the formation of a free tungsten metal phase. The appearance Oxidation was caused by the appearance of wards of free nickel metal in contact with particulate Aluminum oxide is further supported by oxidation of the nickel aluminide fraction in the original wettable powder was generated. The distribution of boron, carbon and oxygen was exclusive of the aluminum oxide phases evenly.

The presence of free tungsten metal was again confirmed by X-ray diffraction studies in which no evidence of a WC or W ^ C phase in the structure was found, although small amounts of these ingredients in the finished coating are not considered to be detrimental Need to become.

Up to Figures 2 through 8 represent x-ray fluorescence photomicrographs the characteristic radiation of the various elements. In this case it became an exaggerated one Piston ring manufactured using a plaama jet injection and

longitudinal sections were used. The figures 2 · ..j £: lg · er Höntgenfluoree * eiwdiagram »e for each of the: later. '.; I renewed chrome »Älekel, tungsten, aluminum,

ORiGfNAL INSPECTED

Carbon, oxygen and boron. The magnification was again 1,100 times.

The piston ring sample analyzed above was designated Sample A, three other experiments were performed, in which the piston rings are made using a plasma gas injection process were coated, in order to confirm the results obtained with Sample A, the parameters specified above were strictly adhered to. These samples were named Samples B, C, and D. In each case, no tungsten carbide was found, neither in the microscope examination nor in the two Bontgen diffraction and free nickel and aluminum were found in all samples.

Samples A through D were used to determine the volume fraction also analyzed the various phases available. These are given in Table I below. As can be seen from this, The tungsten free phase formed a substantial part of the alloy and in most cases the largest part Proportion of the alloy in relation to the volume.

Table I. Volume fraction of the various phases present

Phase A B C D

Tungsten 57.0 % 44.0 % 50.0 % 5 ^, 6 %

Hickel, Chromium 39.8 49.7 48.9 4-3.6 (Hi-Gr) (32) (38) (44) (34) CHi) (7) (10) (5) (10)

Aluminum oxide 1.6 6.2 ^ t ¹ 1 »8

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Samples A through D also had microhardness data determined. A Knoop indenter with a load of 25 g was used and the impressions obtained were measured at a 500-fold enlargement of the diameter. As from the in the following (The data given in Table II shows the tungsten phase surprisingly hard what the interstitial hardening proves positive, since it is known that normally a tungsten phase per se is a comparatively soft one Material is.

Table II

.: ' Micro hardness data

Knoop hardness numbers (KHN) Sample nickel-based tungsten-based

"A 950-1820 2700-3900

B JOO - 1400 2300 - 2500

C -500-1000 1600

D 850 - 950 2600 - 2800

Although there is no direct conversion from Knoop values to Vickers values above about 1000, a corresponds to Knoop value of about 1800 to a Vickers value of about 3000, which shows that the tungsten phase in each of the above Trap has a Vickers hardness of at least 2500.

Figures 9 to 14 show one with the one described above hard tungsten metal alloy coated base material. The piston and cylinder assembly 10 of FIG. 9 is particularly illustrative generally a common 4-ring groove internal combustion engine piston, that works in an engine cylinder. The order 10 consists of a piston 11 and a motor cylinder

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with a bore 13 »which receives the piston 11. Of the Piston 11 has a head 14 with an annular band 15 four ring grooves 16, 17 »18 and 19 attached to the circumference. The upper part of the annular groove 16 has a therein split solid cast iron seal or fire piston ring 20. The second annular groove 17 has a split one fixed second sealing ring 21, which is slightly wider (wider) than the ring 20. The third annular groove 18 carries a two-part oil control ring assembly 22. Die fourth or bottom ring groove 19 carries a three-part oil control ring assembly 23

As in the Pig. 10, the upper seal or fire ring 20 has a main body 24 made of "cast iron, preferably spherical gray iron, has a carbon content of about 3 »5% by weight. The outer circumference 25 of this The ring is covered with an alloy coating 26 according to the invention applied by a plasma jet.

As shown in Fig. 11, the second sealing ring 21 has a main body 27 made of the same cast iron how the body 24 of the ring 20 is made. The outer periphery 28 of the body 27 is upwardly and inwardly of the The lower edge of the ring is inclined and a circumferential groove 29 is provided around this inclined circumference. The groove is filled with alloy 26.

As shown in Fig. 12, the oil control ring assembly 22 in the third ring groove 18 consists of a one-piece flexible ring channel 30 and a sheet metal expanding ring 31 with legs extending into the channel for expanding the ring «30. The ring $ 0 and the expansion ring are described in more detail in USA-Fatena 3 281 156. The one-piece oil control ring 30 has a Fear axially at a distance of-

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arranged, radially projecting band beads 32 on. The beginning of these band beads 32 is with the upper pull 26 Mistake.

In FIG. 13, the oil control ring assembly 23 has a elastic spacer expansion ring 33, which supports and spreads the split thin rail ring 34 ·. The arrangement 33 is of the type described in U.S. Patent 563,739. The outer circumference of the rail rings 34- is provided with the upper pull 26 according to the invention.

From the above description it can be seen that the treads (Support surfaces) of the sealing and oil control rings 20, 21, 22 and 23 with the inventive, a free tungsten phase containing alloy are coated. These treads 26 roll off the bore 13 of the engine cylinder 12 and are sealingly, and the hinge are compressed in the bore 13 so that they are firmly against the Spread the wall of the bore and maintain a well * sealing, sliding contact with it.

As shown in FIG. 14, the upper parts 26 are on the hinge, for example, applied to the hatched binge 21 »by placing several binge on one Axis 35 placed one on top of the other, the hinge being pressed together so that their split ends almost butt against each other. That the pile of rings in their closed, compressed position cohesive axis can be fixed in a turntable and the circumference of the hinge can so be processed so that grooves 29 are formed. The outer circumference of the rings 21 on the axis is then made of a plasma

jet spray gun 36 is provided with the upper pull 26. The «spray gun 36 consists of an insulating housing 3? of, for example, nylon, of which a rear electrode 38

ORtGINAL INSPECTED

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protrudes, the projection of which can be adjusted by a threaded knob 39. ^{A front electrode 2} K) takes up on the front of the housing. The housing 37 and the electrode 40 are hollow and surrounded by a water jacket so that a coolant can circulate between them from an inlet 41 to an outlet 42. The plasma gas jet is introduced through an inlet 45 into the chamber formed by the housing 37 and the electrode 40 so that it flows around the electrode 38.

The front end of the electrode 40 forms a nozzle outlet 44 for the plasma flame and the components for the Preparation of the alloy of the coating 26 are carried out through a powder inlet 45 immediately before the outlet of the nozzle inserted into the nozzle.

A plasma consisting of ionized gas is generated by passing the plasma gas from inlet 42 through a generated between the electrodes 38 and 40 electrical Arc conducts. This plasma gas is non-oxidizing and consists of Sticksotff or argon in conjunction with Hydrogen. The plasma flame emerging from the nozzle 44 As a result of the suction effect pulls the powder forming the alloy with it and brings the powder to such high temperatures, that an alloy is created from it. The wettable powder is usually suspended in a carrier gas. The gas stream carries the alloy into the lower part of the groove of each piston ring and fills the cap.

That into the powder inlet 45 of the spray gun 36 is preferred imported powder consists of tungsten carbide, cobalt, nickel, chromium, boron and aluminum in the proportions given above.

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The preferred deposited coating 26 is a tungsten alloy in which the tungsten-boron free phase is molten and alloyed nickel-chromium matrix is bound. Free nickel can be present and the boron hardens interstitial the free tungsten «Alloy 26, like them 15 is explained in situ in the groove 29 and along with the base body 27 of the ring a common interface or welded zone 46. This interface or zone 4-6 is made up from the materials of the alloy 26 and the material of the ring body 27.

During application by a jet spray process, the temperature in the groove 29 is expediently maintained so that excessive melting and burning off of the body metal 27 is prevented and a rapid quenching of the hardening of the nickel-aluminum alloy matrix is also achieved. For this purpose, the axle with the rings is preferably cooled by an external flow of inert gas which impinges on both sides of the jet flame. It is convenient to maintain the on-axis temperatures of the rings 21 at about 2CW- ⁰ C (400 ° F) or less. It is not necessary to be coated with the plasma jet

A.

To subject rings to a subsequent heat treatment, one only has to allow the rings to cool in the air.

The powder introduced into inlet 4-5 is preferred by gas suction, vibration, a mechanical drive etc. dosed. All of the powder is completely melted and penetrates the inner cone of the plasma jet flame.

When the alloy coatings 26 are made in a groove to form a band around the circumference of the piston ring around, for example, the body metal of the ring is used

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as a protruding part along the groove to form an instantly rapidly collapsing surface for the Ring as described in U.S. Patent 3,133,739. The inclined circumference of the ring 21 can be made by grinding or by torsional twisting of the ring when used in the ring groove, as in the United States patent 3,133,739.

The operation of the plasma gas jet process is better explained with reference to Fig. 16, which shows a spray gun of this type and its mode of operation. A spray gun 47 is shown therein, which is attached at 48 can be. An electrode holder 49 and an electrode 50 are also shown therein. The spray gun will cooled by a coming from a coolant source 51 Coolant circulates in it. The arc 52 is generated by an energy source 53. The plasma gas, the one Combination of nitrogen or argon with hydrogen to avoid excessive oxidation is used at 54 supplied. The wettable powder that is in a carrier gas is shown suspended, enters at opening 55 and is in the area of plasma flame 56 in nozzle 57 introduced. The plasma flame is made naturally by ionization and combustion of the plasma gas is generated. Furthermore, a base material is shown as workpiece 58 on which a coating material 59 is sprayed on using a spray stream 60. As stated above, the spray gun is used moved at an oblique angle across the base material to produce multiple layers that form the Form the finished overall coating.

The following examples are ramlegierungsüberzügen preferred embodiments of the method of the invention for manufacturing hard Wolf, the tungsten itself as separate

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Include alloy phase, explain. The invention is but in no way limited to these preferred embodiments.

example 1

A powder mixture of the composition given below was prepared with the aid of those described above Plasma jet spraying on an axis with oil control rings and sealing rings sprayed on:

40 ,8th Wt% WoIfram carbide 6th W. cobalt 38 Il nickel 6th , 7 Il chrome 1 η boron 0 It aluminum

Best iron with small silicon and carbon impurities

The rings were provided with the hard tungsten coating, whereby the following parameters were observed in the special procedure:

Distance between spray gun and workpiece 15 »24 - 16.5 cm

(6.0-6.5 inches)

Angle between spray gun

and oil scraper rings 0 (vertical

thereon)

Angle between spray gun

and sealing rings 45

Feed speed of,

Primary gas (N ₀ ) 2.41 - 2.55 no

^d (85-90 ft. 3)

at a pressure of 3.52 kg / cm (50 psi)

Feed speed of,

Carrier gas (N ₀ ) 1.42 - 1.56 ψ

^d (59-55 ft. ⁵ )

at a pressure

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3 »52

Feed rate; of the secondary gas (IL,)

DC current intensity DC voltage Feed rate of the

Powder

vertical loading speed Rotation speed of the axis

0.65-0.77 (23-27ft, at a pressure of 3.52 kg / cm ^ (50 psi)

500 - 525 amps 80 - 86 volts

4.76 kg Γ. _Λ "" (10.5 pounds) per hour

71.1-81.3 cm (28-32 inches) per minute

60-90 rpm

(Diameter

10.16 cm (4 inchesX

The hard tungsten coating was then tested for hardness and had a Vickers hardness number based on that Tungsten phase, averaging 2836 and a corresponding Knoop hardness of 1781.

This particular coating was also made according to the photomicrographs given in the description of Figures 1-8 Process analyzed. This analysis showed that the tungsten phase was practically free of carbon and was present in the form of a free phase, which was in a hard nickel-chromium matrix - phase was included. Free nickel metal and aluminum oxide were the other smaller components.

Example 2

The powder of Example 1 was again after the plasma jet spray ζ proceed, but with slightly changed process conditions, which are given below, sprayed on:

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Process parameters

Distance between spray gun and workpiece

Angle between spray gun and oil control rings

Angle between spray gun and sealing rings

Primary gas feed rate (No)

Feed rate of the carrier gas (N \ ^)

Secondary gas feed rate (H ^)

DC current intensity DC voltage Feed rate of the powder

Axis rotation speed 9.5 - 10.8 cm

(3 3A - 4 1A inches

45 °

2.44 - a, 89 m ⁵ (86 - 88 ft. 3) at a pressure of 3.52 kg / cnr (50 psi)

1.4? - 1.56 m ³ (52 - 55 ft. 5) at a pressure of 3.52 kg / cm ² (50 psi)

0.65-0.77 ψ> (23-27 ft3) at a pressure of 3.52 kg / cm ^ (50 psi)

475 - 500 amps 90 volts

4.76 kg (10.5 pounds) per hour

90-120 rpm (4 inches diameter)

Here, too, the hard tungsten coating had a Vickers hardness number greater than 2500 based on the tungsten phase and the photomicrographs showed the presence of a free one Tungsten metal phase. A hard nickel-chromium matrix phase was also present along with free nickel metal and aluminum oxide as other small components of the alloy coating.

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In addition to nickel-chromium and nickel-aluminum, other alloys can also be used as matrix material, e.g. B. Nickel-iron, nickel-copper-molybdenum and Mone! Alloys.

Claims i

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Claims (38)

Claims 1. Metal alloy , characterized in that it has an alloy matrix which contains a separate tungsten phase hardened interstitially with boron. 2. Alloy according to claim 1, characterized in that the tungsten phase has a hardness of more than about 2000 Vickers 40 DPN. 3. Alloy according to claim 2, characterized in that it has a hardness of 2500 to 3500 Yickers-40 DPN. 4. Alloy according to claim 1, characterized in that the volume fraction of the tungsten phase is at least 35% . 5 * Alloy according to claim 4, characterized in that the volume fraction is 35 l> is 60 % . 6. Alloy according to claim 1, characterized in that the matrix is a Hlckel-chromium matrix. 7. Alloy according to claim 6, characterized in that the tungsten phase has a hardness of more than about 2000 Vickers 40 DPN. 8. Alloy according to claim 7 «characterized in that the tungsten phase has a hardness of 2500 to 3500 Vickers-40 DPN. 9. Alloy according to claim 6, characterized in that ^ he volume fraction of the tungsten phase is at least 35 % . 109830/1257 10. Alloy according to claim 9 »characterized in that that the volume fraction is 35 to 60%. 11.! Alloy according to claim 6, characterized in that that it also contains free nickel. 12. The alloy of claim 11 characterized in that it contains free nickel in an amount less than about Contains 6% by weight. 13. Alloy according to claim 6, characterized in that the hardness of the nickel-chromium matrix is more than 800 Vickers-40 DPH is. 14. Alloy according to claim 13, characterized in that the hardness of the Hickel-Chromium-4Iatrix 850 to 1600 Vickers-40 DPH is. 15. Alloy according to claim 1, characterized in that that it contains boron in an amount of from about 1 to about 7% by weight. 16. Alloy according to claim 6, characterized in that it contains boron in an amount of about 1 to about 7 wt .-% contains 17. Alloy according to claim 6, characterized in that that it is produced by plasma jet spraying of a powder mixture consisting of tungsten carbide, nickel, chromium, Consists of boron and aluminum. 18. Alloy according to claim 17 »characterized in that that it also contains cobalt. 109830/1257 19. Alloy according to claim 18, characterized in that it is produced by plasma jet spraying of a powder which has the following composition: 25 to 55 wt% tungsten carbide 4- until 8th II cobalt 25th until 45 η nickel 3 until 7th If chrome 0.5 until 7th η aluminum 1 until 7th U boron The remainder is essentially iron. 20. Use of the alloy according to one of claims 1 to 19 as a hard coating material which is made from interstitial with boron hardened tungsten in a nickel-chromium alloy smatr ix and that by rapid quenching hardened with a plasma flame on a cooled workpiece became. 21. Use of the alloy according to one of claims 1 up to 19 for the production of a hard coating material, which consists of tungsten interstitially hardened with boron in a nickel-aluminum alloy matrix and by means of fast Quenching a plasma flame on a cooled workpiece. has been hardened. 22. Use of the metal alloy according to claim 1 for coating the running surface of a piston ring. 23. Use according to claim 22, in which the alloy coating is produced in situ on the tread » Use according to claim 23, in which the alloy coating is applied to the piston ring by a plasma jet. 109830/1217 Use of the alloy according to claim 6 for coating the running surface of a piston ring. 26. Use according to claim 25 »in the case of the metal coating is generated in situ on the tread. Use according to Claim 26, in which the alloy coating is applied to the piston ring with the aid of a plasma jet is applied. 28. Use of the alloy according to claim 19 for coating the running surface of a piston ring in situ with the aid a plasma jet. . 29. 'Process for the production of the tungsten alloy according to one of claims 1 to 19 »characterized in that the tungsten carbide is converted into tungsten in an oxidizing flame of a plasma arc torch and the tungsten with Boron is combined. 30. Process for covering objects according to the Plasma jet spraying process that uses a plasma flame spray gun that has a combustion spray chamber which is supplied with plasma gas from an appropriate source, in which one is in the chamber An electric arc is generated to ionize and ignite the gas, using a spray metal powder and introduces this into a spray nozzle connected to the chamber, whereby the metal powder melted and guf a base material called the workpiece serves, is deposited, whereby this base material is coated with the liquid metal, the coating is produced by moving the spray gun against the workpiece, so that several superimposed thin 109030/1257 Metal layers are deposited, characterized in that the powder used is tungsten carbide and boron with at least one further alloying element and the plasma gas used is hydrogen in combination with nitrogen or argon, the hydrogen at a rate of 0.566 to 0.850 v? (20 to 30 ft. ⁵ ) per hour under standard conditions and the spray gun is held from the workpiece about 8.9 to about 16.5 cm (3.5 to 6.5 inches), thereby removing the base material with a hard upper train is provided, which consists of an alloy matrix which contains a separate tungsten phase hardened interstitially with boron. 31. The method according to claim 30, characterized in that the spray gun across the workpiece at a rate of 71.1 to 81.3 cm (28 to 32 inches) per minute strokes vertically. 32; Method according to claim 31 »characterized in that that a direct current amperage of 475 to 550 amperes is used to generate the arc. 33. The method according to claim 32, characterized in that an angle between the spray gun and the workpiece from 0 to 55 ° is maintained. 34 ·. Method according to claim 33 »characterized in that that the powder at a speed of 4.5 * to 10 to 12 pounds per hour. The method of claim 34, characterized in that the nitrogen or argon gas is supplied at a rate of 2.27 to 2.69 m ⁵ (80 to 95 ft. ⁵ ) under standard conditions per hour. 109830/1267 36. The method according to claim 30, characterized in that that a piston ring is used as the base material. 37 · The method according to claim 30, characterized in that a powder is used which also contains nickel and chromium, so that the base material is provided with a hard coating which consists of a nickel-chromium alloy matrix which has a separate, interstitial layer
Contains boron hardened tungsten phase. 38. The method according to claim 30, characterized in that the base material with the powder according to claim 19
is covered 59 · The method according to claim 30, characterized in that that the powder is introduced into the spray gun using a carrier gas. 109830/1257