DE1959411A1 - Vacuum evaporation of metals - Google Patents

Description

8 Eiilnckcii. 27, iL: U

Case 28 578-ί ¹

AIR REDUCTION COICPALIY, INCORPORATED
New York, NY, Y.St.A.

Vacuum evaporation of metals

The present invention relates to vacuum evaporation of metals and, more particularly, to a method for evaporating a molten alloy from a single crucible in one
Vacuum wrapping.

Vapor deposition, ie the evaporation of material and its subsequent condensation on a substrate to be coated, has been used successfully in a large number of manufacturing operations. A special ■ steam separator. The method of preparation, which is advantageous when high purity is desired, involves the use of a chilled crucible
and means for heating the surface of the molten material contained in the crucible. The upper

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Surface heating can be done, for example, by means of a suitably directed electron beam or plasma beam or the laser beam is reached. When the crucible cools down, the molten material and the Crucible wall a cover of solidified molten material, which isolates the molten material from the crucible and any reaction between the molten material and the Crucible material prevented.

Methods of vapor deposition known up to now have been satisfactory for many types of material, but have often been used the evaporation of alloys led to difficulties. This is especially true for alloys made from materials with very different volatilities exist, such as alloys of iron plus rare earth metals. For a given heating energy input and radiance the evaporation rate depends on the effectiveness of the vapor deposition system. The effectiveness of the system is, however, determined by a wide variety of different factors that cause changes in the heat balance of the system. Such changes may be a variation of the Result in the amount of solid alloy that is present between the cooled crucible walls and the molten alloy. The melting and solidification of the alloy during the

it ceiling creates a separation of the alloy components and can thereby causing changes in the composition of the molten alloy in the crucible. This can lead to a undesirable change in the composition of the precipitate on the substrate. Simultaneous evaporation of alloying constituents from separate crucibles is one way of avoiding separation problems, but increasing it the cost and complexity of the system high. The evaporation of an alloy from a single crucible can therefore be preferred.

To replenish the molten material in the crucible for from it evaporated during typical vapor separation pre-fermentation

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The alloy is loaded with feed material into the seal. One form of feeding is to use a wire that goes in the path of the radiant heater or directly into the molten alloy in the crucible is passed through the open top of the crucible. Many important alloys lie however, due to the lack of commercial value of the alloy in wire form or not in wire form due to the difficulty of processing the alloy because of its brittleness. Alloys that are in Commercially available in wire form, are often full of dissolved gas and generate a significant amount of uneventfulness Splash when melted in the molten mass.

Cast alloy rods are sometimes preferred over wire for feeding purposes because cast rods are generally purer than wire and of a greater variety. available alloys are commercially available. Such cast rods are generally in excess of 12.7 mm (1/2 inch) in diameter, which in most cases requires relatively slow movement of the rod into the molten weld pool in order to replenish the molten alloy at the rate at which it is is evaporated. This can be difficult because of variations in the system's thermal budget which melt the rod at varying rates and therefore cause significant changes in the actual rate of addition of the new alloy into the molten mass. Under these Umstunden occurs in the "system a Viärmeuna ^T .isgegiiehenhcit on which the upper, erv.äht. th unwanted changes in the LegierimgEzusamnenE-e-estimation zui * has a consequence.

Another difficulty in steam separation sy: - th ·: r. occurs, especially when the crucible in which the £ esc: _ ^ dzene alloy is contained is cooled to form a cover, b-consists in the fact that there is a tendency for condensation to form, L '.;-; ischeii the cover and de ::. v; a ce ergs chilled crucible er.tl; -rr of those: edges of it consists. V.'ULrend des .Ξ-etriecG saiLHolt

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Such condensate builds up and can penetrate between the ceiling and the crucible, resulting in increased mechanical pressure and a concomitant increase in the extent to which 'heat is transferred from the molten material to the cooled crucible' When the molten material is allowed to cool * for example, between oversubscription operations, the solidified alloy often shrinks away from the supporting crucible. During reheating, in general, the same mechanical pressures mentioned above do not develop and the amount of heat transfer is therefore not the same as in the situation described above _β Such changes in the ratio of the volume of the liquid to the volume of the solid alloy between successive operations ?! perform the reasons stated above zn changes in the molten legierungszusamniensetzung Schmelsbaäs, and such changes can not be easily predicted.

It is therefore an object of the present invention to provide an improved method for vaporizing a molten material Alloy from a single crucible in one

A further aim of the present invention is to create a method for the evaporation of alloys with material constituents with widely differing degrees of diversity, with which an improved uniformity of the steam composition can be achieved.

The aim of the present invention is also to provide a method for the evaporation of an alloy ^ "in which the Supplementary speed of the evaporating material is sharply regulated.

Other objects or, objects of the invention will occur to those skilled in the nachfolgendeil description taken in conjunction with the accompanying 'drawing' _s clearly in a vapor deposition

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959411

system for carrying out the method according to the invention schematically illustrated '.

The method of the present invention generally comprises heating the surface 11 of a molten alloy 12 in one go Crucible 13 »to produce evaporation. A solid alloy rod 14 of substantially the same cross-section as that The interior of the crucible is guided upwards from the bottom of the crucible in order to replenish the alloy that has evaporated therefrom. The feeding speed the solid rod is regulated to maintain a substantially constant level of molten alloy to maintain in the crucible.

The vapor deposition system illustrated in the drawing comprises a vacuum envelope or a vacuum housing 16, the Interior is evacuated by a suitable vacuum pump system 17. One with a layer 19 of condensed steam too Covering pad 18 is supported by suitable, not illustrated support means within the envelope 16 in FIG . Positioned along the path of the steam.

The surface 11 of the molten alloy 12 contained in the crucible 13 is heated by means of an electron beam 21. The electron beam 21 is generated by an electron gun which comprises a emission filament or transmitter 22, which is arranged within a recess in a carrier electrode 23. An anode or accelerating electrode 24 is arranged adjacent to the open side of the recess in the carrier electrode, in order to take electrons out of the recess to accelerate, as indicated in the drawing by the dashed lines. The electron beam developed in this way is by means of a magnetic field with curved lines that are concave with respect to the surface 11 through a generally curvilinear path onto surface 11 of the molten alloy 12 is deflected. The magnetic field is shown between a pair of pole pieces 26, one of which is shown is made. An electromagnetic coil 27 is arranged around a core 28 with low magnetic resistance.

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net, which extends between the pole pieces 26 to the Hold pole pieces with opposite polarities. There are suitable, unillustrated feed facilities the required electrical potentials and currents intended for the various components described. An electron beam gun generally of that described The type is described in detail in the ÜSA patent specification 3 177 535 ..

The crucible 13 is provided with an internal passage 29 through which a suitable coolant such as water is circulated can. The crucible is supported within the vacuum envelope 16 on suitable supports, not shown.

A large number of factors contribute to the rate of evaporation. Two factors of major importance are the overall efficiency of the system and the size of the surface area, which is supplied with heat by the impact of the electron beam or another heating beam. The effectiveness of a vacuum separation system can be demonstrated by the expression

H, / H χ 100 are defined, in which H, the theoretically required a ο

The amount of heat required to generate the desired rate of evaporation and HL represent the actual heat input. The lower the heat losses in the system, the higher the effectiveness. If higher temperatures are required to produce evaporation, there will be greater heat loss, which will reduce its effectiveness. For example, cadmium, which has a relatively low vaporization temperature, can in many cases be vaporized with efficiencies above 80 fo. On the other hand, tantalum, which has a relatively high vaporizing temperature, is usually vaporizable with efficiencies typically below 10 f> .

The evaporation rate depends on how bsrslts ürwähnt above, also on the sharpness or the area of the Aufisreffetis of the beam on the surface 11 of alloy 12 ira from the crucible 13. For a given material and a given Bn

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Radiant intensity is the evaporation rate so lower;} e larger the focal point or area of impact. This However, the relationship is not linear and the influences of the Variation of the impact area are for materials with lower Tera tap temperature much lower. The rate of evaporation naturally decreases when the jet sweeps over the entire surface of the molten material, instead of hitting a specific area of it. A sweeping over the jet in this way can lead to more uniform evaporation of the entire surface, of the molten material may be desired. Basically, however, the evaporation rate is easiest with cone soot the total energy supply or the entire heat supply of the electron beam or another heating beam and regulated by regulating the energy density of such a beam, "

Supplementing with a crucible of vaporized alloy, the solid rod 14 of the fermentation alloy is guided upwards in the crucible from the bottom of the crucible. The rod ^has: ■ deti same ^cross-: section as the crucible interior and, therefore, provides the ground or f Interrogator for the 'molten metal alloy' 12 "aear ₀ The ßwgreBgente to äefi l'iegel 13 region of the rod remains äes by Külilimg container to uniaittelbar-below the ^surface. dee gesehmolzenen Scluaelsbaöee fixed .. the "energy beam and -elicähte be regulated so that Oer ScMael.sba'ääurchDie'sser 'BTI exerts surface the Innenaurchmesser'" the seal equal ■ 'is s- so 'öaß "the Sulimelsbad; the "fixed part of the:" staff! 14 completely covered ',' Wemi while heating one. Fluctuation occurs, oil © earlier glades of the rod 14 causes · '·. "Sun does not change Gisli & QT. Schmelzbaäobe ^ flächenbei'eich what to fceiträft j oils Veröampf ^ iigsgeschwindigkeit constant. · -Au hai th _o. ■ .. · '■ io.mSer-äeis carry' the 'avoidance of the .exposure of the-; solid;' end- ■ ■ "öee ö © s staff imü _: the avoidance of the formation; an exposed Becks äaeu. at _9. · a -'constant 'melt-bath composition eiifresB.tsuexhalteii, = the inflow speed becomes longer, e & ie feftäiiruTigsv. * thani3 31.' ■ and- 32 '. regulates ₅ that are in engagement with the sides of the rod and place it in the crucible

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lead towards The feed speed can be regulated by adjusting the speed of rotation of the feed rollers 31 and 52 by suitable means, not illustrated is regulated. For implementations that take a long time Period of time are to be continuous, a relatively large length of the rod 14 can be accommodated by the rod through a suitable vacuum valve 33 in the wall of the envelope 16 is introduced. Thermal insulation 34 can be provided at the lower end of rod 14 to prevent heat loss by keeping the rod-out of the crucible minimal.

The feed rod 14 is moved upward at a speed determined by visual observation of the level of liquid in the molten! Can be molten suitably set _s to this ill 'to keep / eau as constant as possible. Examples of typical Zuführungsgescimindigkeiten are given below and the average speed of the feed depends on the Verdampfungsgeschwiridig ~ Ice it down, ΐ / hen in feeding a mistake should occur · or when a fluctuation in the V / ärmebilanz of the system occurs _s · a fall the Plüosigkeitsleeveaus of the molten bath cause j so the Plussig / Pest interface between the molten weld bath and the solid rod also falls, which means that the liquid level is kept constant. This helps Dei _5, the evaporation rate .and the Schmel-zbadzusammensetsung to keep relatively constant. This is a great advantage when evaporating alloys with components with widely different volatilities, since steady-state conditions help maintain a constant composition in the condensate. The constant upward movement of the feed rod also creates an abrasive effect which prevents condensate from collecting between the rod and the walls of the cooled crucible.

If you use the supplement material in the manner described above introduces into the crucible, a constant level des

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melted Schirielzbades, suitable settings of the Feed rate easy to maintain. It is also the rate of heat transfer out of the crucible out generally constant, which increases the likelihood of changes in ceiling thickness and, as a result, melting and solidification of metal, which produce segregation, is reduced and change the melt pool composition .. As the heat loss can be kept essentially constant in the evaporation according to the invention, the depth of the melt bath can likewise be kept substantially constant, creating a state of equilibrium in which the feed rate the evaporation rate is the same.

The following examples are intended to take advantage of the present Explain the invention further, but the invention is not limited to these examples. Typical feed rates in the examples below can be approximately 2.54 or 5.1 cm (1 or 2 inches) per hour and typical Evaporation rates can be about 0.45 or 0.91 kg (1 or 2 pounds) per hour. The following examples illustrate that the invention is of particular advantage when using elements with widely differing volatilities exist, for example with volatility ratios of 2 or more to 1. The actual volatility ratio doesn't necessarily need to deal with the volatility of the. Elements themselves match, since connections are formed (through intermetallic reactions) that have different volatilities than the elements alone.

example 1

By vaporizing an Fe 25 Cr alloy in the manner according to the invention, a condensate can be produced on a substrate which contains chromium in the range from 23 to 27 % if a feed rod and a crucible interior each 5.1 cm (2 inches) in diameter and 25 kW electron beam energy can be used. In such an alloy, the ratio,

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The volatility of chromium to iron is about 3: 1. In the case of evaporation, in which the supplementary material is introduced into a crucible of the same size from above, when using the same beam energy and an alloy with the same composition, typically only a variation of + 5 ° free of the chromium composition is achieved,

Example 2

When using a crucible with 5 * 1 cm (2 inch) inner diameter and a feed material rod at 5.1 cm (2 inch) diameter made of an alloy with 80 fo nickel and 20 f> iron a 10 kW electron beam can be used to the evaporation of the alloy to cause the i \ ^r i ekel composition is present in the condensate in the range 79.8 to 80.2 fo. In such an alloy, the ratio of the volatilities of iron to nickel is about 2sl "If more conventional procedures are used, the generation of a Niekel composition in the condensate in the range of 79.5 to 80.5 f> can be expected"

Example 3

Using a 5.1 cm (2 inch) inside diameter crucible and an alloy rod made of 25 ° chromium, 6 ° aluminum, 0.4 % yttrium and the remainder of iron, a 15 kV / electron beam can be used to generate evaporation and a condensate with the following composition:

23 to 27 fo chrome

5 to 7 % aluminum '

0.2 to 0.5 fo yttrium.

Using previously known procedures, typical compositional percentages are about double that Dispersion of the composition. The yttrium is about 1/25 times that

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volatile like aluminum, chromium is three times as volatile like aluminum and iron has about the same volatility as yttrium. The circumstances of the volatility do not necessarily coincide with the volatilities of the above elements, what in the formation of compounds is due to intermetallic reactions.

Example 4

An alloy containing 18 $ chromium, 8 $> nickel and the remainder of bison can be prepared by means of the process according to the invention using a crucible with 5 * 1 cm (2 inch) inside diameter in a guide material rod with 5.1 cm (2 inch) BurchirLor .eer evaporate. 3) the resulting Eoftdensat contains 16, ρ to 1 ^,;. ii Ohi'i ^ i / ami 7 Με a # Rleitel, 3 ^ s iron is λΏ / ΐηΐίΓ deXiV.it 1, .τ «- <τΐ 'cuA'jU ^'tA'-ycis"ii; a 2- s ^; £: l so;? lüehtig.v; ici {iara K.Ukol and g:, ;; öhrr.-is Ie ;; i '',.: a "- ·; :: ^ 1 as annoying as that Hicke'i. At \ erwsr.suung vox \ borc ·; · .- ^ li ^r - ^? : --- vraxeii Arbeitsv ^r eieen! '.- ■! .-'«'ij r VerJj.iiz-pfVfT ^ the same L ^ _; .. ..:. ^ ig .v ;; i einir, KoiidGi; -; - '■ ": ■ r *: ii'Chrfü;" im Pö ^ eieh νοΏ 14 eis 2Z> J unö. ^ 'lelcal in the range ν · .:> Vns 1? ^ lead. « ₃

ϊ f i ε »τ> i c λ 5

Site Ltirieru:;? "·, Which contains 6 ^ AluEnium, 4 £ Vanadiian and the rest" iiar, can be found in the erfiänungiigeniäBeri «'eise under Ver ^v ''-^; The formation of a crucible with an internal diameter of 5 cm (2 inch) of a contact material can be evaporated from about the same burial eater. The resulting condensate contains 4 1/2 to 7 1/2 pounds of aluminum and 3 1/2 to 3 1/2 pounds of aluminum 4 1/2 # vanadium. The aluminum is about 50 asal as volatile as the titanium and the volatility of the vanadium is about half that of the titanium is obtained.

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Example 6

An alloy that contains 70. # copper and 30 <fo nickel can be obtained from a crucible with. 5 _} 1 cm (2 inches) inside diameter and vaporized with a feed material (stat) of about the same diameter. The resulting condensate contains 65 to 75 % copper and the balance nickel, with the volatility of the copper being about 50 times the volatility of the nickel. In the case of working methods that are already known, the achievement of a composition with copper in the range from 50 to 90 ia and the remainder nickel can be expected.

™ The foregoing description shows that the present invention is a improved method of vaporizing a molten alloy from a single crucible in a vacuum envelope supplies. An improved uniformity of the condensate composition and the rate of fermentation are achieved of the evaporating material can be sharply regulated.

For the person skilled in the art, the above description will result Modifications without departing from the scope of the invention.

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Claims (4)

PATENT CLAIMS Method for evaporating an alloy from a single crucible in a vacuum envelope, characterized in that that a solid alloy rod of substantially the same cross-section as the interior of the crucible from the bottom of the Insert the crucible upward into the crucible, heat the alloy rod in the crucible to form a molten weld pool, which completely covers the fixed end of the rod, heats the surface of the molten weld pool to evaporate to produce, and the feed rate of the solid rod is regulated to provide a substantially constant " Maintaining the level of the molten alloy relative to the crucible while keeping the alloy with substantially at the same rate at which it evaporates. 2. The method according to claim 1, characterized in that the crucible is cooled. 3> Method according to claim 1 or 2, characterized in that the heat losses from the bottom of the solid Sta.bes regulated out in order to keep it essentially constant. 4. The method according to one.der claims, characterized characterized in that the heating is achieved by means of an electron beam. - 13 009825/1820 Blank page