US3505094A - Titanium-iron eutectic metalizing - Google Patents

Description

P 7, 1970 e. ARUTUNlAN 3,505,094

TITANIUM-IRON EUTECTIC METALIZING Filed May 5. 1966 United States Patent 3,505,094 TITANIUM-IRON EUTECTIC METALIZIN G Gregory Arutunian, Detroit, Mich., assignor to the United States of America as represented by the Secretary of the Army Filed May 5, 1966, Ser. No. 548,368 Int. Cl. C23c 17/00 US. Cl. 11750 5 Claims ABSTRACT OF THE DISCLOSURE A novel method for applying a layer of titanium to a ferrous metal substrate whereby the ferrous metal substrate is heated in a vacuum or inert atmosphere to a eutectic reaction temperature for said ferrous metal substrate and a titanium sample and manipulating said titanium sample while in contact with the heated substrate to cause a titanium-ferrous eutectic coating to be formed on the surface of the ferrous metal substrate.

The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

The present invention relates to a method of producing hard facing coatings on a base of ferrous metal.

More specifically, the invention relates to a new and novel method of applying a greater thickness of corrosion resistant titanium or zirconium metal coating to a ferrous metal than has heretofore been possible.

Although titanium has many industrial applications, its most important chemical property is still its corrosion resistance. This property is attributed to the rapid formation of surface films which are passive in nature and resistant to attack in most oxidizing media.

When titanium is mechanically connected to the more anodic metals, accelerated corrosion will occur. This cathodic effect can produce serious problems since it is often found necessary to aflix titanium to common structural metals, Where large titanium fixtures are attached to small ferrous structures, a severe anodic corrosion will result because of the large cathodic area presented by the titanium fixture.

The corrosion of such anodic metals can be greatly reduced by applying a coating of titanium to the metal to be connected to the titanium structure.

One successful method of titanium coating of ferrous metals has been shown by C. W. Horn et al. in Patent No. 3,071,491. In that method, the absorbed gas in the ferrous metal is driven off by heating the metal in a vacuum. After cooling, a titanium deposit is inserted into the vacuum chamber which is then reevacuated. The titanium is then heated to its vaporization temperature and the vapor is deposited on the ferrous metal. The chamber is then cooled and brought to atmospheric pressure and, later, a diffusion process takes place.

One disadvantage to the Horn et al. method is that as the titanium vapors are deposited on the surface of the ferrous metal, reevaporation of the titanium occurs. This causes the maximum thickness of the coating to be limited to about 0.0025 inch. This limited thickness, while satisfactory for some purposes, is not sufificient for many of todays mechanical applications for corrosion resistance.

It is therefore an object of this inventio nto provide a method for hard facing or metalizing ferrous metals.

It is also an object of this invention to provide a method for metalizing a ferrous metal with a titanium coating.

It is a further object of this invention to provide a method for applying a titanium coating to ferrous metals ice to a greater thickness than possible in known methods.

Another object of this invention is to provide a more efiicient and simple method of applying very thick layers of corrosion resistant titanium on ferrous metals than were previously obtained by vacuum evaporation processes. 1

It is to be noted that this process may also be used to metalize ferrous metals with zirconium although the description below will be limited to titanium for the sake of simplicity.

In general, the coating operation embodied in this method comprises heating a steel base material to 2000 F. F. and placing titanium metal in contact With the steel surface where the coating is desired.

In order to provide an understanding of the principles of the invention, a preferred embodiment shown in the accompanying drawing will be described below. It is understood, however, that no limitation of the scope of the invention is intended thereby since the invention is capable of being carried out in various alternate ways which will be obvious to one skilled in the art without deviating from the scope or the spirit of the invention.

In the drawing, the figure shows apparatus which may be used to carry out the method of the invention.

More specifically, the drawing shows, in a vacuum or inert atmosphere 10, a high-current, low-voltage transformer 1 connected to copper electrodes 2. The copper electrodes 2 are, in turn, connected to opposite sides of a ferrous metal 3 which may be a steel plate.

Application of proper values of current and voltage to the steel plate by means of transformer 1 will cause a heating of the steel plate due to its inherent resistance characteristics. With proper preselection of the voltage and current values, the temperature of the plate can be brought to within :100 F. of a value of 2000" F.

A titanium wire or rod 4 is then moved across the surface to be coated by means of rotary push-pull vacuum feed- throughs 5 and 6. Proper manipulation of the feedthroughs will provide a complete sweep of the area to be coated.

Alternatively, the feed-throughs can be eliminated and the coating can be accomplished by placing titanium sheet metal on the heated steel surface without external pressure.

The process causes a slight reduction of the thickness of the steel sample due to the normal function of the eutectic effect. However, this is more than compensated for by the buildup of the TiFe eutectic coating which, in samples, has been built up to a thickness of inch and more. Basic machining can then be utilized to provide a finished surface on the coating and to reduce it to the exact desired uniform thickness.

The fusion, and consequently, the smearing of the titanium onto the heated steel surface takes place because of the eutectic reaction at 200 F. in spite of the fact that the melting points of steel (2700 F.) and titanium (3200 F.) are not reached in the process.

Thus, it is obvious that the applicant has presented a new and novel method for metalizing ferrous metals with titanium Which represents a great advance in the field of hard facing. The method is susceptible to various changes and modifications within the spirit of the invention which will be obvious to those skilled in the art.

I claim:

1. A process for applying a corrosion resistant coating to a ferrous metal substrate consisting essentially of the steps of:

(a) evacuating a vacuum chamber containing a ferrous metal and a titanium sample;

(b) heating said ferrous metal substrate to a temperature within the range of 1900 F., to 2100 F.; and

3 4 (c) manipulating said titanium sample so as to smear References Cited it onto the surface of said ferrous metal substrate, UNITED STATES PATENTS thereby causing a titanium-ferrous eutectic coating to be formed at the surface of said ferrous metal. 11162449 11/1915 ECkhaYdt 50 X 2. The process of claim 1 wherein the eutectic coating 5 2,327,739 3/1943 Peters 117-200 is formed by the slight eating away of the ferrous metal L 6/1953 PQIIISII 117-200 by reaction with the titanium so as to form the titanium- 2,732,321 1/1956 et a1 1 750 X ferrous coating. ,744,O32 5/1956 Highfield 117-119 X 3. The process of claim 1 wherein the heating of the 2,755,199 7/1956 Rosshelm et a1 3 X ferrous metal is performed by passing a low volta e, hi h 10 3,120,447 2/ 1964 Buck e 117-22 current through said ferrous sample. 3,297,417 1/ 1967 speel'schnflldef 6 X 4. A process for metallizing a ferrous metal b t t 2,295,701 9/ 1942 Wagner 118-76 X consisting essentially of the steps of: 2,424,261 7/ 1947 T ulmln 118-76 X (a) heating said ferrous metal substrate to a eutectic PQREIGN PATENTS reaction temperature for said ferrous metal and a titanium sample in an inert atmosphere; 204054 10/1956 Austraha' (b) placing said titanium sample into contact with said OTHER REFERENCES ferrous metal Substrate; and Metals Handbook, ed. by T. Lyman, American Society (c) manipulating said titanium sample after bringing it into contact with said ferrous metal substrate as for Metals 1948 1219 1221' TA 1948 to cause a titanium-ferrous eutectic coating to be ALFRED L- LEAVITT, Primary Examiner formed at the surface of said ferrous metal sub- Strate J. R. BATTEN, JR., Asistant Examiner 5. A process in accordance with claim 4 wherein said U S C1 XR eutectic reaction temperature ranges from about 19Q0 F. to about 2100 F. 29-196; 117-93, 119, 131; 118-50.1, 76

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