DE1293401B - Process for the production of firmly adhering, gas-tight coatings on molded bodies made of niobium or tantalum or alloys of these metals - Google Patents

Description

1 2

The present invention relates to a method for mainly consisting of metal, a small amount of production of firmly adhering, gas-tight coatings by metal oxide can of course be present therein, application of a silicon-containing metallic layer, without thereby affecting the properties of the over-molded body made of niobium or tantalum or alloy, to be self-proofing is lost,
ments which contain at least 50 percent by weight niobium 5 According to the invention, the metallic layer or tantalum must contain. Vanadium or manganese are contained in order to ensure good adhesion between the particles of the metal layer to produce firmly adhering, gas-tight overlay and between the metal layer and the underlay on molded bodies, preferably of high melting point.

edging metals, such as tantalum or niobium, are known. io (The term “metal” in this description is intended to initially include silicon and boron on the molded body.)
Adhesive oxide layer by oxidation of a metallic coating applied to the glaze by producing the coating in the form of a molded body, a better resistance to glaze is produced. As a metallic coating, a gap penetration is applied by such gases as silicon alloy, which is oxidized; after 15 oxygen, nitrogen or hydrogen, achieved, as it could be achieved with unglazed coatings, the application of a further oxide layer is so strong that the oxide layer melts down like a glaze. It is necessary, however, that the glaze against deletion. Such a coating has the disadvantage that if glaze is resistant. In general, the glaze is the enamel layer cracks or becomes porous, automatically more resistant to devitrification, the more complex the matic formation of the enamel is not possible. 20 is their composition; this is very important for the present invention It is an object glazes, which at relatively low temperatures, the invention to provide a method by which this or about 1100 ⁰ C or less, devitrification ausNachteil is resolved. The invention relates to are thus set. A sufficient degree of resistance in a process for the production of firmly adhering, gas-tight ones is achieved by including at least five EIe coatings by applying a silicon-containing element. The presence of silicon and metallic layer on shaped bodies made of niobium or either vanadium or manganese (or both) is tantalum or alloys, which at least 50 Ge are required, since initially a sintered layer contains the weight percent niobium or tantalum. Elements in metallic form on the object are characterized in that the metallic layer is formed and then oxidized and glazed because it contains the metals listed below within the quantity ranges indicated in a liquid phase (in weight from relative low melting point, which is the percentage):. Sintering the other components to form one

(a) silicon 30 to 50; make it easier to use a firmly adhering coating. It was too

(b) Vanadium or Manganese 5 to 25 or both found that the subsequent incorporation of Vanadium and manganese, a total of 10 to 25, 35 vanadium and / or manganese oxides in the upper and surface layer to form a homogeneous glaze

(c) at least three of the following: contributes.

j _t 1 51-5Q In a preferred embodiment of the

2 ^ ₀ J ₃ 5 to 50 according to the method, a firmly adhering over-

WoIfram 3 to 25 ⁴ ° ^zu ^ ^{from the} metal components of the glaze or

Molybdenum 3 to 25 at least from those metals that are not yet in the

Chromium 3 to 25 basic mass of the shaped body are present

jj _t 3 to 25 ^ ^e surface of the molding applied thereby,

Zircon '3 to 25 ^ ^{since mai1} same into a slurry dips

Aluminum '. ".'. '.''.'.'.'.'.'.'.'.'.'.'.'. 3 to 25 ^{45 or a} _r ^cold " ⁰ ? ^he hot spray process

g α to 15 throws, whereupon it is heated to the coating aui

To melt molded body, to oxidize it and to

the total content of tantalum and niobium glaze. This procedure can also be used

Does not exceed 50 percent by weight, and that will be used to coat molded articles, which earlier

after the drying of the metallic layer of the 50 a protective metallizing treatment

Shaped body in an oxidizing atmosphere so strongly subjected to the same or a different method

is heated so that the metals in the outer layer have become, the final treatment being

of the coating are converted into oxides and neither is therefore made to the general

the oxides melt to form an enamel. To reinforce protection, or to remove parts of

In contrast to the known method, the coating is worn or removed

according to the invention no metal oxide layer, but was to be repaired.

First a metal layer is applied, through which, according to another embodiment of the method according to the invention, an automatic replica of the enamel layer is possible, the metallic constituents are possible. If this becomes cracked or porous, the parts of the glaze or at least those that do not have a metal layer underneath are heated sufficiently high that 60 are contained in the basic mass of the molded body, locally formed oxides, which are then enamelled in the surface of the object to form a will. During the oxidation of the outer layer, a modified surface layer is diffused in, and probably in the layer below one of the shaped bodies is then heated under oxidizing conditions to form the oxide, in order to oxidize the metals in at least one of them, as some are present in the layer 65 to convert the outer layer into the oxides and to melt the metals with a given oxidation treatment oxides to form a glaze,
oxidized faster and to a greater depth The examples below are illustrative than others. It is essential that this layer of the invention and its implementation.

Example I.

A molded body made of niobium is subjected to a vapor degreasing method and a steam jet method subjected using a mild lubricating gel to a fine matte surface achieve.

After degreasing and steam blasting, the molded body, which may already be one Diffusion treatment with silicon and / or other metals has been subjected to a slurry immersed, which consists of the metallic components of the glaze including silicon, vanadium and / or manganese in the form of a powder of 0.075 mm grain size and of a suspension-promoting Agents such as modified bentonite and a binder such as an acrylic resin in toluene consists. The immersion with dryness in between is repeated if necessary to obtain a dry coating of 0.075 to 0.125 mm thickness.

Another method is to use a compressed air spray gun to spray the slurry be sprayed onto the shaped body, drying if necessary in between.

The molded body with the dry adhesive coating is then heated in a vacuum of at least 10 ^-4 mmHg or in argon for 3 hours at 135 ° ⁰ C and to melt at a somewhat higher temperature for a shorter time to the coating and partially into the shaped body to diffuse in, this process is facilitated by the presence of the silicon and vanadium and / or manganese. Finally, the molded body in air for 1 to 3 hours at 1300 ⁰ C is heated to the oxidation and glazing effect of the coating.

If it is a shaped body, which earlier with silicon and / or other metals under Formation of a protective coating has been treated, the first heating in vacuum or Argon is omitted, so the treatment consists of heating in air for about 3 hours at 1300 to 1350 ° C.

The following table gives the composition of two slurries:

A.
Weight B.
percent silicon 33
7th 33
13th Vanadium 7th
7th 0
42 manganese 22nd
7th
7th 7th
0
0 Tantalum 5
0 0
0 tungsten 5
0 0
5 molybdenum chrome titanium Zircon aluminum boron

55

60

The proportions of metals in the slurry correspond to those of the metals in the final Glaze, apart from the diffusion of metals from the molded body.

By varying the proportions of the components of the slurry, it is possible to adjust the reforming temperature to control the glaze. The significance of this phenomenon is that, if the glaze is cracked or perforated, the surface that is then exposed, which is made of metals or a mixture of Metals and metal oxides can be automatically re-glazed as soon as the object is during its use is heated to a temperature above the glaze reforming temperature.

The glaze reforming temperature of the metals of slurry A is about 1200 ^° C., while that of the metals of slurry B is about 1400 ^° C.

According to this method moldings produced a lifetime of 150 to 200 hours at 1300 ⁰ C in oxidizing gases have.

Moldings made of tantalum can be treated in the same way, but the tantalum content in the slurry is replaced with niobium so that the glaze has the same complex composition.

It is the same with moldings made of niobium or tantalum alloys, the metals such as tungsten and Titanium, which are desirable in the glaze, do not need to contain these metals in the slurry to be included. However, by adding a proportion of these metals or some of them to the slurry absorbs, it is possible to increase their proportion with which they are present in the glaze.

Example II

This example is the same as Example 1 with the exception that the adherent coating is hot sprayed, e.g. B. is applied by mud spray or by means of a plasma arc. In addition, the initial heating in a vacuum or in argon can be omitted, so that the melting, diffusing and glazing is carried out in a single heating period in air in about 3 hours at 1300 ^° C.

Hot or cold spraying is particularly suitable for moldings of simple shape, e.g. B. for gas turbine blades, while immersion is to be provided for objects of complex shape, z. B. for combustion chambers of gas turbine engines.

Example III

After degreasing and steam blasting, a molded body made of niobium is converted into a mixture of metal powders from about 0.1 to 0.075 mm grain size together with about 0.5 weight percent potassium fluoride packed, which is in a refractory container, e.g. B. made of aluminum oxide, sillimanite or Mullite, which has a loosely fitting lid. The metal powder contains (in percent by weight) 33 silicon, 7 vanadium, 7 manganese, 7 tantalum, 22 tungsten, 7 molybdenum, 7 chromium, 5 titanium and 5 aluminum.

The container is then heated in a vacuum of at least ΙΟ " ⁴ mm of mercury for 3 hours to a temperature of 1350 ° C or a longer time to 1300 ° C so that the metal powder diffuses in the molded body. The molded body receives a coating that consists of niobium , originating from the molded body, and consists of the metal components of the treatment powder.

After the container has cooled to handling temperature, the molded body taken out and cleaned by brushing off the loose powder and washing in hot water. He

is then 1 to 3 hours in air at a temperature heated from 1300 ° C until the surface is oxidized and the oxides forming a surface layer melted in the form of a glaze.

Example IV

This example differs from Example III in that after cleaning and steam blasting, however, before performing the diffusion and glazing treatment, a surface layer of the Object is modified by allowing titanium to diffuse into it. It was found that this Pretreatment facilitates the subsequent formation of an even glaze.

The diffusion of titanium in the shaped bodies is preferably carried out by heating in vacuo in the manner described above, with the exception that the complex metal powder is replaced by titanium powder of about 0.4 mm grain size and that the heating is carried out at about 1160 for 5 to 10 hours ⁰ C is carried out.

While in Examples I and II the various components of a bath or a spray solution can lie within the same ranges as specified for the metal components of the glaze, there are reduced upper limits for the mixtures used in both Examples III and IV for some metals, namely (in percent by weight)

Manganese 15

Tantalum 25

Niobium 25

Tantalum and niobium together 25

Tungsten 10

Molybdenum 10

Chrome 10

Titanium 10

Zircon 10

Aluminum 15

Boron 10

Claims (1)

Claim: Process for the production of firmly adhering, gas-tight coatings by applying a silicon-containing one metallic layer on molded bodies made of niobium or tantalum or alloys, which contain at least 50 percent by weight niobium or tantalum, characterized in that that the metallic layer includes the metals listed below within the specified Quantity ranges contains (in percent by weight): (a) silicon 30 to 50; (b) Vanadium or manganese 5 to 25, or both vanadium and manganese, 10 to total 25, and (c) at least three of the following: Tantalum 5 to 50 Niobium 5 to 50 Tungsten 3 to 25 Molybdenum 3 to 25 Chromium 3 to 25 Titan 3 to 25 Zircon 3 to 25 Aluminum 3 to 25 Boron 3 to 15 the total content of tantalum and niobium not exceeding 50 percent by weight, and that after the metallic layer has dried, the shaped body is heated so much in an oxidizing atmosphere that the Metals in the outer layer of the coating are converted into oxides and the oxides melt to form an enamel.