US2508509A

US2508509A - Apparatus for coating hollow objects

Info

Publication number: US2508509A
Application number: US572682A
Authority: US
Inventors: Lester H Germer; George E Reitter
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1945-01-13
Filing date: 1945-01-13
Publication date: 1950-05-23
Anticipated expiration: 1967-05-23

Description

May 23, 1950 H. GERMER ET AL APPARATUS FOR COATING HOLLOW OBJECTS Filed Jan. 13, 1945 THROUGH VALVES r0 SUPPLYSOURCE or L11. GERMER GERE/TTER ATTORNEY 'IIJ 'IIIIIIII lNl/ENZ'ORS:

TO VACUUMPUMP THROUGH VALVE SYSTEM Patented May 23, 1950 NITED STATES TUS FOR COATING HOLLOW OBJECTS corporation of New York Application January 13, 1945, Serial No. 572,682

6 Claims.

This invention relates to apparatus and processes for coating metals, such as iron, steel, nickel or other metals, with coatings which may be deposited by decomposition of metallic carbonyls at the surface to be coated.

More particularly, the invention relates to apparatus and processes for more effectively coating interior surfaces of objects, such, for example, as cylinders, objects generally of cylindrical nature, hollow tubes, slotted tubes, etc.

Prior to the present invention there has been suggested apparatus and methods for coating the interior surface of cylindrical objects by means of an arrangement for insertion into the cylindrical interior of the object, said arrangement consisting of a tube for carrying gases of metallic carbonyls with or without other gases into the interior of the object to be coated and delivering these metallic carbonyls to the interior surface through a, plurality of orifices. The space to which the orifices delivered the gases was connected to a vacuum pump for the purpose of maintaining a reduced gas pressure at the surface to be plated. Inasmuch as the surface to be plated was to be maintained hot 25 during the plating operation, the tubeigfor conducting gases into the interior of the object to be plated was maintained cool by a water jacket. In plating hollow cylindrical objects by means of the equipment thus previously suggested it was found that the difierence in gas pressure at the point at which metallic carbonyl gases was supplied and the point at which the gases were removed by the Vacuum pump was considerable. In other words, the gas pressure at various points within the equipment was not uniform which tended to produce non-uniformity of plating or coating and led to other difliculties.

The general object of the present invention is to improve metallic carbonyl plating processes or equivalent processes in which metals are deposited from gases by causing the plating to be more uniform, by reducing the difliculty of maintaining the required low vacuum, by expediting and increasing the rapidity of plating and by providing equipment whereby these improvements may be effectively achieved.

From a generic standpoint a, feature of the invention comprises a movable nozzle and suitable means to move it reciprocatingly, rotarily,

circularly or otherwise to deliver gas within an Apparatus for practicing the invention comprises, in general, a gas-tight water cooled moving injector for supplying metallic carbonyl gases along with other gases, if desired, to the interior or other surface of an object which is to be coated or plated. The space in which the object is located is maintained highly evacuated during the entire operation and the object to be plated is heated by suitable means during the plating process.

Apparatus comprising such a. moving injector has been embodied in difierent forms of equipment of which an exemplary embodiment disclosed in the accompanying drawings has been found to be quite satisfactory.

In the drawings, Fig. 1 is a vertical sectional view through the approximate center of the moving injector machine;

Fig. 2 is a side view of the upper portion of 80 the apparatus shown in Fig. 1 taken at right angles to Fig. l;

Fig. 3 is a detail section taken on the line 3-8 of Fig. 1;

Fig. 4 is a sectional view of the lower end of the injector element taken on the section line 6-8 of Fig. 3;

Fig. 5 is a detail of the reversing screw arrangement taken on the line 5-5 of Fig. 2.

The object I comprises a hollow metallic object havin a somewhat curved interior surface to be plated and typified, in general, any hollow cylinder, hollow semicylinder, or tubular structure to be plated on its interior surface.

In accordance with the prior suggestions above referred to, it has been pointed out that such platings may consist of metals, such as tungsten, molybdenum or chromium, their alloys, or carbides of metals, such as W2C, W5C2, M040, M020, Cr2C or Cr5C2. For the purposes of the present invention, these metals are illustrative only and are intended to typify any of a group of metals and any of a group of metallic compounds or alloys which may be plated by deposition of metal or compounds of metal from metallic carbonyls with or without other gases at a surface in a highly or considerably evacuated space. M(CO) x indicates any suitable metallic carbonyl and X gas indicates any suitable other gas or gases such as pure hydrogen or mixed gases to be used in the plating process. Nickel, iron, and cobalt carbonyls as well as rare metal carbonyls are included. Furthermore, the invention is not limited to any particular purpose for which the plating is to be accomplished. Specifically, and in the present case, the invention has been practiced to produce a surface which is resistant to highly heated corrosive gases. Thus, for example, the object I, by way of example, may be an iron or steel nozzle through which highly heated corrosive gases must pass and is to be plated to make it resistant to such gases.

The injector tube 2 comprises a central bore 3 through which metallic carbonyl gas is led to the interior of the object I. vided with a water Jacket which has two portions 4 and 5 one of which is a water inlet and the other of which is a water outlet. Water is supplied to the inlet through a hose connection 6 and taken oif through another hose connection I, these hose connections being sufliciently long and flexible to permit the tube 2 to be driven up and down throughout the range of its movement by an automatic reversing screw 8. The water inlet and water outlet are tightly connected to tube 2, theconstruction of which is indicated in Figs. 3 and 4 wherein it is shown that the portions 4 and 5 are separated by a septum 9 which causes the water introduced to be driven to the bottom of the tube whereat it passes from the passage 4 to the passage 5 through openings I which are transverse to the closed bottom end of the passages 4 and 5. Power is supplied to the reversing screw v8 by means of a drive shaft II and suitable beveled gears or other means. The block l2 which carries the hose connections 6 and 1 is rigidly connected to the tube 2 and carries a pin I3 which works in the slot I4 of the reversing screw 8 so that the block I2 is driven first upward and then downward with a steady motion and automatically reversed as it reaches the end o1 its motion. Gases such as molybdenum carbonyl, chromium carbonyl or tungsten carbonyl are introduced through a tube I5 illustrated as being made of glass but which may be made of metal or any other suitable material sealed into the flanged cylinder to form an elongated chamber IS in which the upper end of the injector tube 2 reciprocates. At the upper end of the tube the entire cross-section is open down to the point where the water jacket begins and is sealed off from the water jacket space by an annular ring I'I, thus permitting free access of the supplied gases to the interior of the object I and maintaining them cold until they are delivered at the plating point. The space I 6 is sealed at the bottom around the reciprocating tube 2 with a gas-tight seal I8 and the chamber I9 in which the object I is placed is also sealed at the upper end by another seal I8 which is a duplicate of the upper seal but reversely arranged. (Alternatively the upper seal may be replaced by a flexible connection to the injector tube.) These seals per se are of a type well-known in the art for sealing a sliding rod in an air-tight manner against passage of gases and, therefore, the details of their construction need not be discussed. Multiple seals have been used in place of the single seals I8 and experience has indicated that they are more satisfactory. The flanged tube 20 which encloses the chamber I6 is made air-tight at its lower end by gaskets 2| and the flanged tube 22 is made air-tight at top and bottom by similar gaskets 2|. As will be hereinafter stated, the flanged tube 22 tends to become hot but in order to reduce its tendency to become hot the tubes 23 filled with flowing cooling water are provided. These tubes may be made integral with the flanges of the member 22 and the top and bottom The tube 2 is pro- 4 closure members thereof, that is, the heads 24 and 2!. In practice it has been found quite effective, if the tubes 23 are made of copper and are soldered, brazed or welded to the

steel members

22, 24 and 25.

The element I may be supported at a suitable height by means of an annular ring 28 having supporting legs 2! or other suitable means.

A heating coil 28 composed of wire covered with heat resistant insulation, such as asbestos, closely surrounds the central portion of the tube 22 and is Packedwith a covering 28 which, in turn, is covered by a Jacket 20. Tubes 8| lead from the top and bottom end of the space I8 to a suitably powerful vacuum pump or system of vacuum pumps designed to create and maintain a suitably low vacuum in the plating chamber I8. In practice, vacua of from 0.1 to 0.001 inch of mercury have been employed.

In operating the apparatus the lower head 25 is removed and a specimen or object I to be plated is placed in the apparatus at a suitable height determined by the length of the support ing legs 21 or other equivalent adjusting or supporting means. The plate 25 is screwed into place and the vacuum pump set into operation. The vacuum may and should be checked by means of a suitable manometer or vacuum measuring apparatus connected to the outlet tube 8| or the inlet tube I5 or-both, as may be desired. The drive shaft II is then set into rotation, the vacuum rechecked, and, if found satisfactory, electric current may be caused to flow in the coil 28 to heat the specimen to a suitable temperature whereupon metallic carbonyl gas, admixed with other gases if preferred, such as hydrogen, carbon monoxide or similar gases dependent upon the kind of a coating which is desired upon the interior surface of the element I, is admitted. On occasion before introducing any carbonyl gas it may be found desirable to introduce pure hydrogen which, when applied to the hot surface of the element I, tends to clean the surface and promote the adherence of the subsequently applied coating thereto. Temperatures within the range 400" C. to 900 C. are suitable for plating molybdenum from M0(CO)s. For other metals and compounds thereof the temperatures may be suitably chosen in accordance with suggestions previously made known by others. i

The tube 2 operates first downwardly and then upwardly at a suitable traversal rate and for a sufllcient length of time to achieve the necessary thickness of coating whereupon the alternating or direct current in the coil 28 is discontinued-to allow the specimen I to cool, whereupon the apparatus is opened and the specimen is removed. The cycle of operations may thereupon berepeated to plate another specimen.

Obviously, the object I may comprise an object wholly or partly closed at one end such as a vase, a metallic bottle, or a bearing, a cylinder of an internal combustion engine, a cylinder for a as compressor, a hollow die, a gun barrel, a pipe or an extrusion nozzle, all of which examples are cited as illustrative rather than as limiting.

What is claimed is:

1. Apparatus for supplying gaseous metallic carbonyls to the interior of a gun barrel or similar hollow object which comprises a nozzle mountable within the object together with means for moving the nozzle along the bore of the object, means for simultaneously maintaining a high degree of vacuum within the bore of the object,

and means for heating the object to a carbonyl decomposing temperature simultaneously with the execution of the moving operation and the continued maintenance of the vacuum and supply of the metallic carbonyl.

2. In combination for use in plating surfaces, an enclosed space for receiving an object to be plated by decomposition of a gas at the surface of the object, means for establishing a high degree of vacuum in said space, a conduit for supplying gas to be decomposed to the surface of said object, means for moving the conduit within said space in a manner to cause the gas introduced thereby to impinge upon the surface of the object, in combination with means for maintaining the established high degree of vacuum during the movement of the conduit.

3. Plating means comprising an enclosed gastight chamber designed to receive a cylindrical hollow metal object, an injector tube, means for moving the injector tube back and forth within the bore of said object in combination with means for heating the object and means for simultaneously causing the injector tube to remain cool.

4. Apparatus for plating objects with substances including a metal as a constituent comprising an enclosed vessel, means including an outlet therefor for maintaining the high degree of vacuum in said vessel, a moving injector slidably movable back and forth in an opening of said vessel, a seal cooperating with said in- ,iector to maintain an airtight condition therearound, means for supplying gas including a metallic carbonyl through said injector, means for circulating a cooling medium throughout that part of the length of said injector which is at any time within said vessel, and an electrical heating winding surrounding said object adapted to heat said object to a high temperature while within said vessel.

5. Apparatus for plating by decomposable gases comprising means bounding and defining two enclosed spaces, a hollow tube extending at one end into one space through a seal and at the other end into the other space through another seal, drive means coupled to said tube externally thereof at a point between said seals for causing said tube to reciprocate through said seals,

6 means for supplying a metallic carbonyl in gaseous form into one of said spaces, and means for strongly pumping the other space to maintain a gas pressure of a small fraction of an atmosphere therein.

6. Apparatus for plating a surface of an object with material derived from decomposition of a metallic carbonyl, said apparatus comprising a gas-tight chamber for enclosing the object, exhaustion means for continuously maintaining a high degree of vacuum in said chamber, means for heating the surface of said object to the decomposing temperature of said carbonyl while said object is in said chamber under said vacuum, and means including a movable nozzle and a source of metallic carbonyl vapor to cause the stream of gas including the metallic carbonyl to impinge successively upon difierent portions of said surface, said exhaustion apparatus operating at such speed and efilciency with respect to the ingress of said gas to remove gaseous products resulting from decomposition of said metallic carbonyl rapidly enough to maintain a high degree of vacuum until the plating has reached the desired thickness.

LESTER H. GERMER. GEORGE E. REITTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,497,417 Weber June 10, 1924 1,730,087 Needle et al. Oct. 1, 1929 1,758,810 Austin at al. May 13, 1930 1,816,476 Fink et a1. July 28, 1931 1,818,909 Reerink Aug. 11, 1931 1,829,756 Noddack Nov. 3, 1931 1,982,590 Church et al Nov. 27, 1934 2,183,302 Brauer Dec. 12, 1939 2,285,017 Christensen June 2, 1942 2,344,138 Drummond Mar. 14, 1944 FOREIGN PATENTS Number Country Date 306,902 Great Britain June 20, 1930