US2320328A - Application of spray metal to metal surfaced substantially cylindrical objects - Google Patents

Description

Patented May 25, 1943 SURFACE!) SUBSTANTIALLY OILINDRI- car. owners John Frank Meduna, Seattle,

to Metallizing land City, N.

Wash, assignor Engineering 00., Inc., Long Is- Y., a corporation of New Jersey No Drawing. Application August 6, 1942,

Serial No. 453,904

9 Claims.

This invention relates to new and useful improvements in theappllcation of spray metal to trsfietal-surfaced substantially cylindrical ob- In industrial practice, a coating of metal is frequently applied to metal-surfaced cylindrical objects such as shafts, sleeves or the like by metal spraying. For this purpose, the metal to be applied is projected, against the surface to be covered, in the form of a spray, the particles of which are in a molten or heat plastic condition. As a rule, metal spraying isv carried out with the use of metal spray guns, 1. e., devices in which the metal is fed toa heating zone from which zone metal particles, at least some of which are molten or ina heat plastic condition, are propelled against the surface to be sprayed, by a blast of air or other gas. The application of spray metal for such purpose may, for example, be carried out to protect the surface as for instance a shaft or sleeve surface against corrosion, to provide a, coating of the desired ornamental or hearing characteristics or to build up worn sections or parts.

In making spray metal coatings, particularly in the formation or re-building of hearings or other working surfaces of machine parts, it is essential that the'applied spray metal adheres to the surface to which it is applied with a high degree of bond, for, otherwise the applied spray metal will come off. For the purpose of securing the requisite degree of bonding, the surface to which the spray metal is to be applied is as a rule suitably pie-conditioned. In the past, such pre-conditioning treatment has been generally of two kinds. Mechanical roughening and heating. Mechanical roughening of a metal surface to adapt the same to receive and retain applied spray metal must be of a type involving the formation of a multiple number of closely spaced cavities with peened and splayed edges and interspaces, forming a multitude of keyways. In the past the most common method of procuring such type surface has been by sand or grit blasting. Sand or grit blasting, however, is in many cases unsatisfactory and will often 'not yield a surface capable of bonding applied spray metal with a satisfactory degree of bond. Spray metal has a tendency to shrink and in many cases the sprayed or grit blasted surface of for instance a shaft or sleeve does not provide a sufilcient bonding surface to prevent the separation of the applied spray metal coating from the base particularly under working conditions. Furthermore, many machine tools or machine tool parts of essentially cylindrical configuration as for instance generator shafts or the like are inherently unsuitable for sand or grit blasting.

An alternative form of mechanical surface roughening for spray metal bonding purposes is that of machine roughening the surface to be sprayed in a particular manner designed to procure the above-mentioned surface characteristics essential for spray metal bonding. This surface roughening method, however, is subject to the same inherent limitations and drawbacks as the one involving sand or grit blasting.

The heating method of surface conditioning a .metallic base to bond thereto applied spray metal involves the heating of the surface to a relatively high temperature and to spray the hot surface with metal. This method is not widely used and requires, as a general rule, considerable skill and elaborate equipment and is relatively expensive. Furthermore, in most cases the tem perature to which the surface or base must be heated is so high that it tends to warp or otherwise destroy the article to which the metal spray is to be applied.

There is one basic limitation inherent in practically all of the hitherto used conditioning methods for rendering metal surfaces capable of satisfactorily bonding applied spray metal. This limitation resides in the fact that the methods are not adaptable to hardened metal articles or surfaces. Thus many hardened shafts or sleeves for instance cannot be properly surface conditioned by mechanical roughening procedures such as grit or sand blasting or roughmachining. On the other hand the heating method is not feasible for most such articles as they will soften and thus lose their hardness if they are heated to the temperatures necessary to secure the desired degree of bonding to the spraymetal applied thereto. 'Though partly hardened shafts or sleeves or similar articles of cylindrical circumference have been prepared by grit or sand, blasting using very hard grit such as aluminum oxide abrasives, nevertheless the bond obtained is usually very unsatisfactory.

One object of the invention comprises, inter alia, a procedure for the conditioning of metalsurfaced substantially cylindrical objects and particularly of shafts, sleeves, rods, bars and the like toreceive' and retain thereto applied spray metal substantially free from the limitations hereinabove expressed in connection with hitherto-known practices. This and further objects of the invention will be seen from the following description. i I

Whereas my copending application Serial No. 453,903, relates broadly to the deposition and bonding of small amounts of electrode material as a preconditioning step in the application of spray metal to metal surfaces, the instant ap-- plication covers specifically the deposition of small amounts of electrode material bonded onto a rotating cylindrical metal surface as hereinafter more fully set forth.

In accordance with the invention a substantially cylindrical object of metal or having a metal surface, which is to receive a layer of spray metal with a high degree of bond, is conditioned for the spraying step by rotating the object about its axis, establishing contact between the metal surface of the object, and a metal electrode, electrically heating the contacting surfaces of the electrode and the metal surface by means of an electric current, flowing, under conditions of resistance heating, through said contacting surfaces while said object is rotating, to firmly bond electrode material to the metal surface and causing small amounts of electrode material to be left deposited on the -metal surface along the path of travel of the electrode when in contact with the metal surface while the object is rotating.

The metal electrode that I may use in accordance with the invention is preferably of the wire type, i. e., of the type in which a wire or bar, whether round, flat or of any other shape, constitutes an electrode. For best results, I have found that a nickel wire electrode particularly of the commercial nickel wire type gives satisfactory results. nickel wire constitutes a satisfactory wire electrode. It is of course understood that electrode size and elecric current should be suitably coordinated.

Rotation of the cylindrical object within the procedure of my invention may be accomplished in any desired manner. I prefer, however, to rotatably mount the object in a suitable lathe, or such similar machine. For most efficient operation, I prefer rotational surface speeds not 'metal surface of the object to be conditioned for the metal spraying operation is established in the ordinary manner by placing the electrode in direct contact with such surface. In principal, it is immaterial whether the cylindrical object is brought to rotation before electrode contact therewith is established or' whether such electrode contact is first established and the .cylindrical object thereafter caused to rotate. Within thepreferred embodiment of my invention, however, I find it of advantage to establish electrode contact with the metal surface of the cylindrical object while the same is already in rotation.

Within the range of normal requirements there are no critical limitations with respect to the metal of the surface of the cylindrical objects in relation to the metal of the electrode that A /a commercial may be used. Nickel has proven a satisfactory electrode. If in some cases, however any particular electrode metal should prove unsuitable or unsatisfactory in the application of my method in connection with a given metal of an object to be surface conditioned for spraying, the operator can determine by a few simple emperical tests as to which electrode metal to select for best results. As a practical guide, any two metals that can be joined by heating will operate as electrode material and surface to be conditioned for spraying.

The electric heating step of the contacting surfaces of the metal electrode and metal surface to be conditioned formetal spraying may be effected by placing the electrode and the .metal surface in electric circuit with a source of electric energy in such manner that the circuit is closed, while the cylindrical object is rotating, by contact between the metal surface of the object and the metal electrode. This may be for instance suitably arranged by connecting one lead from the source of electric energy to the work piece and the other lead to the electrode. When placing the object and particularly the metal object of cylindrical shape such as a shaft, sleeve, rod. bar or the like into a lathe. I prefer to connect one lead to either the lathe steady-rest or the lathe tailstock. In case the work piece is chucked without use of steadyrest or tailstock, the lead should be suitably connected directly to the work piece to avoid current passing through the lathe bearings. The conditions of current flow in the circuit upon closing the same are so adjusted that conditions of resistance heating at the contacting surfaces of electrode and metalsurface exist. By conditions of resistance heating I mean that the current flowing through the contacting surfaces is in amount and intensity sllfilcient to cause heating at the contacting surfaces by the resistance offered the free flow of the current by reason of the joint constituted by the contacting sur-' faces.

Though voltages having a wide range including relatively high voltages of the order of magnitude of 100 or 200 volts may be usedin accordance with the invention, I prefer to use voltages of a lower order of magnitude. One of the reasons for the preference for a lower voltage range is that higher voltages have a tendency to are badly particularly when making and breaking contact between the electrode and the metal surface whether the making and breaking be deliberately induced or caused by the unevenness of the rotating surface treated. Though relatively v mild arcing may be beneficial in the procurement of a satisfactorily conditioned surface, excessive arcing is under normal conditions an undesirable aspect impairing satisfactory deposit of electrode material in accordance with the invention. Considerable amounts of metal may be lostas the result of the high temperatures caused by the are thereby tending to render the procedure less efficient. Furthermore, arcing is attended by operational difficulties which would often require a greater skill on the part of the operator and/or suitable control mechanism. A still further disadvantage of excessive arcing is the formation of metal oxide which may tend to impair the bond in certain casesbetween the conditioned surface and thereto applied spray metal. I prefer there'- fore to soadjust the conditions of current flow in the circuit that, upon closing or'breaking the same, the current intensity is sufficiently low to avoid excessive arcing and yet have the current in amount and intensity sufficient to cause the desired deposition and bonding of electrode material.

While very low voltages such as even fractions of one volt can be used and give, when applied with care, fairly satisfactory results, such low voltages are as a rule not desirable for largerscale efficient operations as they require the use of relatively small or at least fairly sharp pointed electrodes so that the procedure is slow. In general a satisfactory current will depend upon the voltage, the size of the electrodes and principally 7 upon the amount of contact between the electrode and the metal surface of the base to be sprayed. These factors may be easily adjusted to suit particular conditions. I have found that an average voltage from to 20 volts gives satisfactory results. For best results, however, I find that ordinarily a voltage range of from 2 to 9 volts is to be preferred in the majority of cases. The amount of current to be used may vary over a wide range depending upon the factors hereinabove recited. As a general rule, however, when using a wire electrode, I prefer a current in excess of 200 amperes and most preferably a current of the order of magnitude of about 300 to 400 amperes. Thus for instance a 300 ampere current gives good results with a nickel wire electrode. When using larger electrodes the use of larger amounts of current may be necessary.

The deposition of small amounts of electrode material within the procedure in accordance with my invention may be caused either by the melting off of small amounts of electrode material from the tip of the electrode or by pulling off small amounts of surface bonded electrode material from the tip of the electrode when moving the latter. In the majority of cases, deposition of electrode material may be caused in both of these manners. Moving of the electrode as for instance in a stroking contact making and breaking manner will thus cause small amounts of electrode material to be left deposited and firmly bonded tothe area of the rotating surface to "which the electrode contact was applied. The

electrode inaterial is thus deposited on the metal surface along the path of travel of the electrode when-incontact with the surface while the object "is rotating.

Within the preferred embodiment of my invention, the metal surface to be conditioned for spray metal application, when inserted in circuit as above set forth with ajsuitable metal electrode and a suitable source of electric energy is repetitiously contacted and preferably repetitiously contact stroked with the electrode on successive areas while the object is rotating; the stroking action depositing on these areas small amounts of electrode material along the path of travel of the electrode when in contact with the rotating surface. While this procedure essentially involves breaking and making contact between the face.

mended as the generated heat may heat the electrode to a point where the operation becomes ineflicient by reason of an undesired excessive metal deposition. In many cases, where special conditions or circumstances may require or render advisable continuous electrode contact, suitable precautionary measures including proper selection of electrode contacting surface, proper coordination of currentamounts, suitable electrode cooling etc. may overcome this disadvantage or at least reduce the same to a tolerable minimum. If desired, the electrode may be held or mechanically fed to the rotating surface in a substantially intermittent or continuous contact stroking manner arranged so as to deposit individual electrode material deposits. The contacting procedure whether continuous or intermittent is continued or repeated until the surface to be sprayed is satisfactorily covered with electrode material.

I have found that it is not necessary to have every spot on the metal base covered by the deposited material, but that on the contrary, it is sufficient to deposit a large number of small, closely spaced, amounts of electrode'metal with spaces in between some of them. The size of the spaces between deposited electrode material particles may be varied over a reasonably wide range at the judgment. of the operator. Broadly stated, the smaller the spaces the stronger a bond will result and therefore where a strong bond is not desired the particles may be quite widely spaced. For a strong bond, however, I prefer to have spaces between particles not appreciably in excess of 3%".

When proceeding in accordance with the invention, the size and spacing of the projections and craters 0n the surface of the electrode deposited metal are as a rule substantially of the same order of magnitude as the size of spray metal particles in the spray metal layer. When making at least some of the electrode metal deposits relatively large, aided if necessary by increases in amperage, the resulting irregular patterned surface of the herein described type and characteristics will includelarger size projections normally of an order of magnitude in excess of that of spray metal particles. These larger type projections of higher order of magnitude, though not necessarily acting as interlocks with spray metal particles of the subsequently superimposed layer of spray metal, nevertheless; contribute to the bond by counteracting or pre-- venting slippage of the spray metal layer with respect to the base surface resulting from the shrinkage of the applied spray metal.

The amount of the ited on the base as well as the size of the larger type irregular projections, if such are produced, may be varied to suit conditions or requirements. When a heavy spray metal coating is to be depos ted, I prefer to make some of the larger type projections of deposited electrode metal relatively large and some of these projections may thus, for instance, extend as much as or even more. However, where a thin coating such as a 3%" coating is to be applied by metal spraying, I prefer to keep the height of these larger type projections at less than the thickness of the sprayed metal coating to be applied, i. e., less than 3 as otherwise if the sprayed metal coating is machined smooth, these projections will extend through the coating to the machined sur- There are, however, some applications where this is no disadvantage.

electrode material deposlarger projections, if such are desired, relatively so high that they will extend to beyond the thickness of the coating of sprayed metal that'is to be applied, and then machine off or tool off their tops so that they willnot project through the sprayed metal coating to be applied. Thereafter, the spray metal coat may be applied.

If desired, small amounts of electrode metal may be deposited, as described previously, to the base and then the process continued so that more electrode material is deposited on top of electrode material previously deposited, as well as in the spaces, between previously deposited electrode metal. By this continued application of electrode material, a relatively thick coating of electrode material may be applied. Within normal re- -quirements, the thickness of the coating of electrode material has, in itself, ordinarily no effect upon the bond obtained, nor upon the satisfactory operation of the method.

Aside from any irregular pattern of electrode material, the latter may be deposited upon the rotating base in any other pattern or series of patterns. posited in either small successive or continuous amounts in strips or ridges substantially circular in arrangement or they .may be deposited in separate individual relatively small isolated spots,

or in a criss-cross pattern.

The following example is furnished by Way of illustration and not of limitation:

Example The' source of electrical energy, consisting of a transformer, connected to an alternating current For instance, the metal may be depower supply, is first provided, capable of an I averagevoltage between two and nine volts and approximately 400 amperes. A one-inch steel shaft of 'S. A. E. 1045 steel which is to be'coated by metal spraying on. a section of its length is mounted in a lathe, between lathe centers. One lead from the source of electrical energy is connected to the tailstock of the lathe. The other. lead from the source of electrical energy is con- I nected to a nickel wire of approximately diameter. The shaft is rotated in the lathe at a speed of approximately 600 revolutions per minute, and while the shaft is rotating, the nickel wire is first contacted with the surface of the shaft to be conditioned and as soon as the metal electrode starts to melt, the surfaceof the shaft, while still rotating, is lightly and repetitiously stroked with the nickel-wire over successive areas of the same, whereby'the end of the nickel wire is caused tomake and break contact repetitiously with success" portions of the surface. After the desired surface area has been substantially covered by relatively closely spaced amounts of deposited nickel from the nickel wire electrode,- the treatment is discontinued and the surface is now ready to be sprayed upon.

As afore pointed out, any common metal may be used as electrode metal on practically any base. Thus,;for instance, such metals or alloys as steel, copper, bronze, zinc, silver, monel, aluminum, brass, cast iron, steel, stainless steel, inconel, or the like may be used either as electrode metal or as base upon which the electrode metal is to be deposited. In most cases, however, I

prefer for best results nickel, bronze or silver as of the invention a wire electrode, I

prefer to use 76 'wircs, whether round or fiat shaped, having a maximum cross-sectional width substantially between and inch.

The source of electrical energy useful in accordance with my invention may be one proan appearance resembling frozen foam, froth or 4 lava essentially representing a structure of substantially microscopic porosity on at least the surface thereof. Nickel electrode deposited material in particular typifies such frozen foam, froth or lava resembling surface structure.

Although the principle of the application of the electrode material involves the use of heat produced by electric energy, the heat is produced at the relatively small surface of contact between the electrode and the rotating base. It is not necessary to heat up the whole base appreciably in the performance of my method.

I have found that the processes of preconditioning a' metal surface for spray metal bonding as herein described can be performed under water. While this would not generally be desirable for ordinary work, it may be of advantage under special circumstances or requirements. In this connection use of the process under water or even with the use of an aqueous medium as cooling agent may be used to prevent overheating in the application of the process.

Where non-oxidizing conditions are desirable, the process in accordance with the invention may be conducted in an inert atmosphere.

The procedure in accordance with my invention offers the further advantage in that it permits the preconditioning of a metal'surface, obje'ct 'or "base, the surface of which consists of spray metal. In the past, spray metal surfaces, particularlywh'en machined smooth could not be properly conditioned for spraying. When speaking of a metallsurface or metal base or where -"use is made of ,an expression of similar import, I

I mean to include a spray metalsurface.

My novel method also permits the surface preparation-or conditioning of certain cylindrical objects that require metal spraying ononly a part for instance a bearing section of a'generator'shaft. As grit blasting must be done inn-closed room and as no machinery,

of their.; surface as .such as .a la'the, can be used in the grit blast roomjit has a rule inconvenient if not altogether impractical to grit or sand blast such objects.

When I speak of or contemplate a cylindrical surfa'cein connection with the application of my process, I mean to include such surface both of outside as "well as of inside diameter.

The foregoing specific description is for pur poses of illustration and not of limitation and it is therefore my intention that the invention be limited only by the appended claims or their equivalents wherein I have endeavored to claim broadly all inherent novelty.

I claim:

1. Inthe method for applying spray metal to a metal-surfaced substantially cylindrical object with a high degree of bond, the improvement which comprises conditioning the metal surface of such cylindrical object for spray metal bonding by rotating such object about its axis contacting multiple small areas of the metal surface of said object with a metal electrode while said object is rotating, including, establishing contact between the metal surface of said object and such metal electrode, electrically heating the contacting surfaces of said electrode and said metal surface by means of an electric current flowing, under conditions of resistance heating, through said contacting surfaces while said object is rotating, to firmly bond fused electrode material to said metal surface, and causing small amounts of electrode material to be left deposited on said metal surface along the path of travel of said electrode when in contact with said metal surface while said object is rotating to thereby obtain a surface characterized by an irregular roughness with a multitude of projections with overhanging edges and minute craters with overhanging edges, and thereafter spraying metal onto the metal surface of such cylindrical object thusly conditioned. j

2. In the method for applying spray metal to a metal-surface with a high degree of bond, the improvement whichcomprises conditioning the metal surface of such cylindrical object for spray metal bonding by rotating said object about its axis, a first operation for depositing small amounts of surface-bonded electrode material involving establishing contact between the metal surfaces of such object and a metal electrode,

electrically heating the contacting surfaces of said electrode and said metal surface by means of an electric current flowing under conditions of resistance heating, through said contacting surfaces, while said object is rotating, to firmly bond fused electrode material to said metal surface, and causing small amounts of electrode material to be left deposited on said metal surface along the path of travel of-said electrode when in contact with said metal surface while said object is rotating, and depositing additional small amounts of electrode material over successive areas of said metal surface by successively repeating said first metal deposition operation over said areas while said object is rotating to thereby obtain a surface characterized by an irregular roughness with a multitude of projections with overhanging edges and minute craters with trode, rotating said object about its axis, repetitiously contacting successive areas of small metal surface with said electrode, under conditions of material firmly bonded thereto obtaining a surface characterized by an irregular roughness with a multitude of projections with overhanging edges and minute craters with overhanging edges, and thereafter spraying metal onto the metal surface of such cylindrical object thusly conditioned.

4. In the method for applying spray metal to a metal-surfaced substantially cylindrical object,

the improvement in accordance with claim 3 in which said successive areas of said metal surface are repetitiously contacted with said electrode by stroking said surface with said electrode.

5. In the method for applying spray metal to a metal-surfaced substantially cylindrical object with a high degree of bond, the improvement which comprises conditioning the metal surface ofsuch cylindrical object for spray metal bonding by positioning the metal surface of such object and a nickel wire electrode in electric circuit with a source of electric energy so as to close said circuit by contact between said metal surface and said nickel wire electrode, rotating said object about its axis, repetitiously contact stroking successive areas of said metal surface with said nickel wire electrode, under conditions of current flow in said circuit sufficient to heat and firmly bond fused nickel from said nickel wire electrode on said metal surface upon so closing said circuit, to thereby deposit on said areas, along the path of travel of said nickel wire electrode when in contact with the rotating surface, small amounts of nickel from said nickel wire electrode firmly bonded thereto obtaining a surface characterized by an irregular roughness with a multitude of projections with overhanging edges and minute craters with overhanging edges, and thereafter spraying metal onto the metal surface of such cylindrical object thusly conditioned.

6. In the method for applying spray metal to a metal-surfaced substantially cylindrical object, the improvement which comprises conditioning the metal surface of such cylindrical object for spray metal bonding by positioning the metal surface of such object and a metal wire electrode in electric circuit with a source of electric energy so asto close said circuit by contact between said metal surface and said wire electrode, rotating said object about its axis, repetitiously contact stroking successive areas of said metal surface which said object is rotating with said wire electrode under conditions of resistance heating at an average voltage of substantially from to 20 volts to thereby deposit on said areas, substantially along the path of travel of said wire electrode when in contact with said rotating surface, small amounts of fused metal from said Wire electrode firmly bonded to said metal surface obtaining a surface characterized by an irregular roughness with a multitude of projections with overhanging edges and minute craters with overhanging edges, and thereafter spraying metal onto the metal surface of such cylindrical object thusly conditioned.

7. In the method for applying spray metal to a metal-surfaced substantially cylindrical object the improvement in accordance with claim 6 in which said average voltage is substantially from 2 to 9 volts.

8. In the method for applying spray metal to a metal-surfaced substantially cylindrical object with a high degree of bond the improvement which comprises conditioning the metal surface of such cylindrical object for spray metal bond..

ing by positioning the metal surface of such object and a nickel wire electrode in electric circuit with a source of electric energy so as to close said circuit by contact between said metal surface and said nickel wire electrode, rotating said object about its axis, repetitiously contact stroking successive areas of said metal surface while the same is rotating with said nickel wire electrode under conditions of resistance heating at an average voltage of from 2 to 9 volts to thereby deposit on said areas, substantially along the path of travel of said electrode when in contact with said rotating metal surface, small amounts of fused nickel from said nickel-wire electrode firmly bonded to said metal surface obtaining a. surface characterized by an irregular roughness with a multitude of projections with overhanging edges and minute craters with overhanging edges, and thereafter spraying metal onto the metal surface of such cylindrical object thusly conditioned.

9. In the method for applying spray metal to a metal-surfaced substantially cylindrical object with a high degree of bond, the improvement which comprises conditioning the metal surface of such cylindrical object for spray metal bonding by axis-rotatably mounting such object, positioning the metal surface of said object and a metal electrode in electric circuitwith a source of electric energy so as to close said circuit by contact between said metal surface and said electrode, rotating said object about its axis repetitiously closing and opening said circuit by repetitiously making and breaking contact between said electrode and successive areas of such metal surface under conditions of current flow in said circuit sufficient to heat and firmly bond fused electrode material on said metal surface upon so closing said circuit to thereby deposit on said areas, along the path of travel of said electrode v .Pateht No. 2,320,328.

GE RTIFIc TE 01 CORRECTION.

' a 5. 19 5. JOHN FRANK HEDUNAf It s hereby certified that erroreppears in the printed specification efthe ebove numbered patent requiring correction as follows: 29.56 5, first eolumn, line 67, claim 5, for "small" read said--; and second column,'

line 52, claim 6, for. "which' read -while--; and that the said Letters Patent should. be read with this 'eerreeti'on therein that the same ma? con-:

iorm to the record of the case in the Patent Office.

Signed and eel'ed this 29th day of Juhe, A. D. 191,6.

Henry Van Are'dale .(868-1) Acting Co nmissioner of Patents.