EP0057505B1

EP0057505B1 - Process and apparatus for treating electrically conductive matrices, solutions for use in such a process, and products thereof

Info

Publication number: EP0057505B1
Application number: EP82300139A
Authority: EP
Inventors: Joseph Ady
Original assignee: Metafuse Ltd
Current assignee: Metafuse Ltd
Priority date: 1981-01-13
Filing date: 1982-01-12
Publication date: 1988-07-27
Also published as: PT74270B; FI820063L; BR8200154A; EP0057505A3; NO820075L; DK11082A; PL234879A1; GR75834B; PT74270A; IL64706A0; EP0057505A2; DD202312A5; AU7944882A; DE3278814D1; KR830009257A; CA1187035A

Description

The present invention relates to fusion processes, apparatus for carrying out such processes and the products of such processes, and solutions for use in the process.
It will be understood that for the purposes of this application that the term "fusion" is employed as meaning a process whereby diverse elements are chemically or physically bonded.
It has been a common practice to treat substrates or matrices in different manners to enhance the characteristics of the matrix for a particular application. Sometimes these treatments have involved the matrix as a body and in other techniques only the surface characteristics are enhanced.
However, these techniques have had limitations. The workpiece or matrix may be of a certain form which does not lend itself to the subjection of a particular characteristic-enhancing process; the process may be destructive of the already desirable characteristics of the work-piece; or the treated work-piece while having certain enhanced characteristics may exhibit other reduced characteristics.
Generally, the process employed depends upon the work-piece or matrix to be treated and the characteristics desired.
More specifically, coating techniques, heat treatment, anodizing, arc spraying, vacuum evaporation, chemical deposition, sputtering, and ion plating are all common processes.
Non-ferrous metals may be hardened by aging, heat treatment or anodizing.
These techniques however, do not provide adequate protection against dry rubbing wear.
Spray coating techniques have not improved corrosion resistance or the physical properties of ferrous materials.
The wear resistance of non-ferrous substrates have been improved by electrochemical or electromechanical plating with hand chromium but these are expensive and time consuming.
The use of a pulsed current has been suggested as a means of improving the electroplating process, for example in the following references:

(i) Plating, August 1969, pages 909-913, Vol. 56, No. 8, V. E. Lamb: "Electroplating with Current Pulses in the Microsecond Range".
(ii) US Patent 3802854 to Mueller-Dittman et al. However this prior art disclosed electroplating methods in which the whole of a body to which a metal is to be applied, is immersed to a bath containing that metal in some form. Accordingly, if only a discrete area of the body's surface is to be plated, it is necessary to mask the remainder of the surface, which makes such a process inconvenient to use..

The other techniques arc-spraying, vacuum evaporation and sputtering have their shortcomings in that the coating deposited is usually thin, the interfacial bond strength is poor, or can only be used to treat small surface areas.
They have disadvantages in use in that they employ gaseous techniques or high voltages which are difficult in practice and limit their versatility.
For convenience of reference, in this description, the term "first conductive element" shall refer to the matrix with which fusion is to be accomplished; and the term element" shall refer to such an element or an alloy thereof; the term "second conductive element or an alloy thereof" shall refer to the element which is to be fused with the matrix.
It will also be understood that the term "fusion" as used in this specification means a penetration by the atoms or molecules of a second element within the solid matrix of a first element or alloy thereof.
According to the present invention there is provided a process for the fusion at ambient temperature of about 20°C of at least one second conductive element comprising ferrous and non-ferrous metals or an alloy thereof, present in a dissociable form as part of a solution, into a matrix of a first conductive element comprising the steps of:

(a) placing the solution having a resistivity of in the range of 5 to 500 ohms cm in contact with a selected limited area of the adjacent surface of said first conductive element comprising ferrous and non-ferrous metals or an alloy thereof;
(b) applying an interrupted half-wave electrical pulsing signal in the range of 2.5 microseconds to 28.6 nanoseconds with a frequency in the range of 400 Hz to 35 MHz to said solution and said first conductive element, said signal being applied have an amplitude of 3 amps per 0.3 square mm whereby said second conductive element is fused with said first conductive element in said selected area without substantial generation of heat to a depth of more than 0.5 um thickness.

The invention provides a process for fusing a wide variety of conductive elements in either ferrous and non-ferrous matrices.
In particular, in the preferred arrangements described, the process creates high bond strength without distortion or loss of work piece or matrix properties. The process does not require gas-air operation and does not involve safety hazards.
Preferably, the solution comprises .a process as claimed in Claim 1 characterized in that said solution comprises:

0.10 to 10% by weight of a first compound including said second metal in a dissociable form;
at least one of a stabilizing complexing agent which maintains the first compound in solution and an organic catalyzer for promoting the speed of reaction; and
a solvent chosen from the group comprising water, an organic solvent or a mixture thereof. The solutions may have a pH in the range 0.4 to 14. Advantageously the resistivity of the solution is in the range of 10 to 80 ohm cm.

By the application of the process to ferrous or non-ferrous matrices new products are produced, in which a second chemical conductive element has been deposited to heights exceeding 0.5 pm.
These and other objects and features of the present invention will become more apparent from the following description and drawings in which certain specific embodiments of the process apparatus and products of the process are illustrative of the invention and in which:

Fig. 1 is a general perspective view of an embodiment of the apparatus in accordance with the invention being used in accordance with a process of the present invention;
Fig. 2 is a schematic electrical circiut employed in the present invention;
Fig. 3 is a circuit diagram of an oscillator as employed in apparatus in accordance with one embodiment of the present invention;
Fig. 4 is a composite SEM photomicrograph with right-hand and left-hand halves, of a copper matrix with which molybdenum has been fused using the process of the present invention with a molybdenum solution. The left-hand half has a magnification x1250 and the right-hand half is a x8 enlargement of the marked area of the left-hand half.
Fig. 5 is a graph of an SEM/EPMA scan across the sample shown in Fig. 4 and shows the fusion of molybdenum with copper;
Fig. 6 is a composite SEM photomicrograph, with right and left hand halves, of a steel matrix with which molybdenum has been fused using the process of the present invention with a molybdenum solution. The left hand half has a magnification x1250 and the right hand half is a x8 enlargement of the marked area of the left hand half;
Fig. 7 is a graph of an SEM/EPMA scan across the sample shown in Fig. 6 and shows the fusion of molybdenum with steel;
Fig. 8 is a composite photomicrograph, the right and left hand halves, of a copper matrix with which tungsten has been fused using the process of the present invention with a tungsten solution. The left hand half has a magnification x 1250 and the right hand half is a x8 enlargement of the marked area of the left hand half;
Fig. 9 is a further SEM photomicrograph of the sample of Fig. 8 with a magnification x 10,000 of part of the marked area of Fig. 8;
Fig. 10 is a graph of an SEM/EPMA scan across the sample shown in Figs. 8 and 9;
Fig. 11 is a composite photomicrograph, with right and left hand halves, of a steel matrix with which tungsten has been fused using the process of the present invention with a tungsten solution. The left hand half has a magnification x1310 and the right hand half is a x8 enlargement of the marked area of the left hand half;
Fig. 12 is a graph of an SEM/EPMA scan across the sample shown in Fig. 11 and shows the fusion of tungsten with steel;
Fig. 13 is a composite photomicrograph with right and left hand halves of a copper matrix with which indium has been fused using the process of the present invention with an indium solution. The left hand half has a magnification x1250 and the right hand half is a x8 enlargement of the marked section of the left-hand half;
Fig. 14 is a graph of an electron microprobe scan across the sample shown in Fig. 13;
Fig. 15 is a composite SEM photomicrograph, with right and left hand halves of a steel matrix with which indium has been fused using the process of the present invention with an indium solution. The left hand half has a magnification x625 and the right hand half is a x8 enlargement of the marked section of the left hand half;
Fig. 16 is a graph of an SEM/EPMA scan across the sample shown in Fig. 15;
Fig. 17 is a composite SEM photomicrograph, with right and left hand halves, of a copper matrix with which nickel has been fused using the process of the present invention with a nickel solution. The left hand half has a magnification x 1250 and the right hand half is a × enlargement of the marked section of the left hand half;
Fig. 18 is a graph of an SEM/EPMA scan across the sample shown in Fig. 17;
Fig. 19 is a composite SEM photomicrograph with right and left hand halves, of a steel matrix with which nickel has been fused using the process of the present invention with a nickel solution. The left hand half has a magnification x 1310 and the right hand half is a x8 enlargement of the marked section of the left hand half;
Fig. 20 is a graph of an SEM/EPMA scan across the sample shown in Fig. 19;
Fig. 21 is a composite photomicrograph of a copper matrix with which gold has been fused. The left hand half has a magnification x1310 and the right hand half is a x8 enlargement of the marked section to the right hand half.
Fig. 22 is a graph of an SEM/EPMA scan across the sample shown in Fig. 21 showing gold fused in the copper matrix;
Fig. 23 is a composite photomicrograph with right and left hand halves, of a steel matrix with which gold has been fused using the process of the present invention with a gold solution. The left hand half has a magnification x1310, the right hand half is x8 magnification enlargement of the marked area of the left hand half;
Fig. 24 is a graph of an SEM/EPMA scan across the sample shown in Fig. 23 showing gold fused in the steel matrix;
Fig. 25 is an SEM photomicrograph with a magnification x10,000 of a copper matrix with which chromium has been fused using the process of the present invention with a first chromium solution;
Fig. 26 is a graph of an SEM/EPMA scan across the sample shown in Fig. 25 and shows the fusion of chromium with copper;
Fig. 27 is an SEM photomicrograph with a magnification x10,000 of a steel matrix with which chromium has been fused using the process of the present invention with the first chromium solution referred to above;
Fig. 28 is a graph of an SEM/EPMA scan across the sample shown in Fig. 27 and shows the fusion of chromium with steel;
Fig. 29 is a composite SEM photomicrograph, with right and left hand havles, of a copper matrix with which chromium has been fused using the process of the present invention with a second chromium solution. The left hand half has a magnification x625 and the right hand half is a x8 enlargement of the marked area of the left hand half;
Fig. 29A is a further enlarged SEM photomicrograph of the enlarged area of Fig. 29 at a magnification of xl 0,000;
Fig. 30 is a graph of an SEM/EPMA scan across the sample shown in Fig. 29 and shows the fusion of chromium with copper;
Fig. 31 is a composite SEM photomicrograph, with right and left hand halves, of a steel matrix with which chromium has been fused using the process of the present invention with a second chromium solution. The left hand half has a magnification x1250 and the right hand half is a x8 enlargement of the marked area of the left hand half;
Fig. 31A is a further enlarged SEM photomicrograph of the enlarged area of Fig. 31 at a magnification of x 10,000;
Fig. 32 is a graph of an SEM/EPMA scan across the sample shown in Fig. 31 and shows the fusion of chromium with steel;
Fig. 33 is a composite photomicrograph with right and left hand halves, of a copper matrix with which cadmium has been fused using the process of the present invention with a first cadmium solution, the left hand half has a magnification x1310 and the right hand half is a x5 enlargement of the marked area;
Fig. 34 is a graph of an SEM/EPMA scan across the sample shown in Fig. 33 and shows the fusion of cadmium with copper;
Fig. 35 is a photomicrograph at x11,500 magnification of a steel matrix with which cadmium has been fused using the process of the present invention with a second cadmium solution;
Fig. 36 is a graph of an SEM/EPMA scan across the sample shown in Fig. 35 and shows the fusion of cadmium with steel;
Fig. 37 is a composite photomicrograph with left and right hand halves, of a copper matrix with which tin has been fused using the process of the present invention with a first tin solution; the left hand half has a magnification of x655 and the right hand half is a x8 enlargement of the marked area;
Fig. 38 is an SEM/EPMA scan across the sample of Fig. 37 and shows the fusion of tin with copper;
Fig. 39 is a composite photomicrograph with left and right hand halves, of a copper matrix with which tin has been fused using the process of the present invention with a second tin solution; the left hand half has a magnification x326 and the right hand half is x8 enlargement of the marked area;
Fig. 40 is an SEM/EPMA scan across the sample of Fig. 39 and shows fusion of tin with copper;
Fig. 41 is a composite SEM photomicrograph with right and left hand halves, of a steel matrix with which tin has been fused using the process of the present invention with the second tin solution; the right hand half is a x1310 magnification and the left hand half is x8 magnification of the marked area;
Fig. 42 is a SEM/EPMA scan across the sample of Fig. 41 and shows fusion of tin with steel;
Fig. 43 is an SEM photomicrograph at a x5200 magnification of a copper matrix with which cobalt has been fused using the process of the present invention with a first cobalt solution;
Fig. 44 is an SEM/EPMA scan across the sample of Fig. 43 and shows fusion of cobalt with copper;
Figs. 45 and 45A are photomicrographs of a copper matrix with which silver has been fused using the process of the invention with a first silver solution;
Fig. 45 is a composite with the left hand side having a magnification of x625 and the right hand side being an x8 enlargement of the marked area;
Fig. 45A is a further enlarged SEM photomicrograph of the enlarged area of Fig. 63 at a magnification x 10,000;
Fig. 46 is an SEM/EPMA scan across the sample of Fig. 45 and shows fusion of silver with copper;
Fig. 47 is an SEM photomicrograph at a magnification of x10,000 of a copper matrix with which silver has been fused using the process of the present invention with a second silver solution;
Fig. 48 is an electron microprobe scan across the sample of Fig. 47 and shows fusion of silver with copper.

In these Figures which are graphs, of Figures 5 through 48, the vertical axis is logarithmic while the horizontal axis is linear. And in these graphs the surface layer has been taken as the point at which the concentration (wt%) of the matrix and the element which has been fused therewith are both at 50% as indicated by the projections.
Referring now to Fig. 1, this drawing illustrated, in general perspective view, an apparatus in accordance with the invention in which one output of an oscillator 11, powered by a power supply 10, is connected to an electrode 19 through an insulated handle 20. The other output of oscillator 11 is connected, via line 16 and clamp 15, in the matrix or substrate 14 which is to be treated by the process of the invention. By these connections the electrode is positively charged and the matrix is negatively charged when the signal is applied.
The material to be fused is in the form of a solution held in a reservoir 17 which is connected by a tube 18 to the electrode 19. Electrode 19 is in the form of a plate incorporating a main channel 21 into which one side of the oscillator 11 output is led. Channel 21 has a series of side channels 22 which open onto the undersurface of electrode 19. The flow from reservoir 17 is by gravity or by a pump and may be controlled by a valve such as 23 on the handle 20. For further control, more even distribution of the solution, and to prevent the inclusion of foreign matter the surface of electrode 19 is preferably covered by a permeable membrane such as cotton or nylon.
It has been found that in effect fusion that the application of 50,000 watts/sq. cm. or alternatively the application of current of the order of 10,000 amps/sq. cm. is necessary.
From a practical standpoint 10,000 amps/sq. cm. can not be applied constantly without damage to the matrix to be treated.
However, it has been found practical to apply a pulsing signal of 2.5 microseconds to 28.6 nanoseconds having a magnitude of 3 amps to the electrode and this causes fusion to occur over an area of approximately 0.3 sq. mm.
To effect fusion over an area with the apparatus shown in Fig. 1 the electrode 19, matrix 14 and the oscillator output are connected as shown.
The operator passes the electrode 19 in contact with the upper surface of the matrix over the matrix surface at a predetermined speed to apply the electrode material to the matrix and fuse it therewith.
It has also been found that the continuous application of an alternating signal generates considerable heat in the substrate or matrix and to overcome this heat build-up and avoid weldments the signal generated in the present apparatus is a half-wave signal which permits dissipation of the heat.
As will be apparent to those skilled in the art each material, both the matrix and the material to be applied have specific resistance characteristics. Thus with each change in either one or both of these materials there is a change in the resistivity of the circuit.
In Fig. 2,

R_i=the resistance of the electrode,
R₂=the resistance of the matrix, and
R₃=the resistance of the circuit of 10 and 11.

Variations in R₁ and R₂will lead to variations in ths frequency of the signal generated and the amplitude of that signal.
As mentioned previously a signal having an amplitude of 3 amps is believed to be the preferred amplitude. If the amplitude is greater decarbonizing or burning of the matrix takes place and below this amplitude hydroxides are formed in the interface.
Fig. 3 is a schematic diagram of an oscillator circuit used in apparatus in accordance with the present invention.
In that circuit a power supply 30 is connected across the input, and across the input a capacitor 31 is connected. One side of the capacitor 31 is connected through the LC circuit 32 which comprises a variable inductance coil 33 and capacitor 34 connected in parallel.
LC circuit 32 is connected to one side of a crystal oscillator circuit comprising crystal 35, inductance 36, NPN transistor 37 and the RC circuit comprised of variable resistance 38 and capacitance 39.
This oscillator circuit is connected to output 50 through, on one side capacitor 40, and on the other side diode 41, to produce a halfwave signal across output 50.
In the apparatus actually used the several components had the following characteristics:

31=1.₂ farad
32=0.3 picrofarad
33=0-25 millihenrys
35=400-30 Khz
36=20 millihenrys
37=NPN
38=3.5 p farads
39=0-500 ohms
40=₄₀₀ p farads
41=diode

To maintain the amplitude of the signal at 3 amps R, resistance 38 is varied; to vary the frequency inductance 33 is varied.
If C=the capacitance of the circuit of Fig. 2 and R" R₂ and R₃ are the resistances previously characterized it is believed that the optimum frequency of the fusing signal F_o may be determined by the form
where
and

C=capacitance of the circuit
- L and C may be determined by any well-known method.
F_a depends on the material being treated and the material being applied but it is in the range 400 Hz-35 MHz. The frequency, it is believed, will determined the speed of the process.

To fuse a predetermined area, the area is measured. Since each discharge will fuse approximately 0.3 sq. mm. then the travel speed may be determined by the following formula:

and

A=area to be covered in sq. mm.
F, is the number of discharges per second.

As mentioned previously the resistances R, and R₂ may be measured by any known means.
However it has been discovered that the measurement of resistance in the liquid phase may not be stable. In this situation the resistance is measured in a standard fashion. Two electrodes, 1 cm. apart and 1 cm. sq. in area are placed in a bath of the liquid phase and the resistance was measured after a 20 second delay. After the variable parameters have been determined and the apparatus, matrix and probe have been connected as shown in Figs. 1 and 2, the probe 13 is passed over the surface of the matrix in contact therewith at the predetermined speed.
The process may be more clearly understood from the following specific examples.
In each of these examples the electrode was so connected as will be apparent from the description, so that when charged the electrode is positively charged and the matrix is negatively charged.
With respect to the fusion of a second conductive element into the solid matrix of a first conductive element, using a solution of the second conductive element, with respect to each solution, the process was carried out at the ambient temperature, 20°C, in the following manner.
The matrix 14 metal was connected into the circuit as previously described. The frequency was determined in accordance with the formula previously set forth and the solution in reservoir 17 applied by movement of the electrode over one surface of the first metal for varying periods of time as determined by Form 11. To ensure uniform distribution of the second metal solution over the surface of the first metal the electrode was covered with cotton gauze or nylon. It will be apparent that other materials may be employed. This arrangement also served to limit contamination of the solution when graphite electrodes were employed. They had a tendency to release graphite particles in the course of movement.
The treated samples were then sawn to provide a cross-sectional sample, washed in cold water, subject to ultrasonic cleaning, embedded in plastic and ground and polished to produce a flat surface and an even edge. With other samples with the softer metals where there was a tendency to lose the edge on grinding two cross-sections were secured with the treated surface in face to face abutting relationship, embedded as before and ground and polished.
Following embodiment the sample was etched using Nital for steel, the ferrous, substrate, and Ammonium Hydrogen Peroxide on the copper, the non-ferrous substrate.
During the course of some applications it was found that adjustments were sometimes required in either the frequency, or speed of application. These were due to changes in the solution composition or variations in the matrix.
A semiquantitative electron probe microanalysis of fused interfaces were performed using an Energy Dispersive X-Ray Spectroscopy (EDX) and a Scanning Electron Microscope (SEM).
The surface of the embedding plastic was rendered conductive by evaporating on it approximately 20 µm layer of carbon in a vacuum evaporator. This procedure was used to prevent buildup of electrical charges on an otherwise nonconductive material and a consequent instability of the SEM image. Carbon, which does not produce a radiation detectable by the EDX, was used in preference to a more conventional metallic coating to avoid interference of such a coating with the elemental analysis.
Operating conditions of the SEM were chosen to minimize extraneous signals and the continuum radiation and to yield at the same time the best possible spatial resolution.
The conditions typically used for the elemental analyses by EDX were as follows:
Energy calibration was tested using AI kd emission at 1.486 keV and cuK at 8.040 keV.
A standardless semiquantitative analysis was adopted for determination of elemental concentration, using certified reference materials (NBS 478, 78% Cu-27% Zn and NBS 479a, Ni, 11 %, Cr 18%, Fe) to verify results. Multiple analysis of reference materials were in excellent agreement with certified values from NBS. Average precision of ±1 % was achieved. A size of analyzed volume was calculated from the following equation 1:
where

R_(x) is the mass range (the x-ray production volume)
p=Density of analysed material
E_o=The accelerating potential
E_c=A critical excitation energy.

The diameter of analysed volume was calculated for typical. elements analysed and was found to be as follows:
For assessment of the diffusion depth a static beam was positioned across the interface at intervals greater than the above mentioned mass range. Ensuring thus the accuracy of the analysis.
The results of elemental concentration were given in weight percentage (wt%) for each of the measured points across the fusion interface.
In the various examples which will be described the second conductive element, that is the element to be diffused into the matrix, is present in solution. In some solutions small quantities of metallic ions of a third metal are also provided. The presence of these metal ions is believed to be required as complex forming agents to facilitate fusion. Small quantities of organic catalysts such as gum acacia, hydroquinone, animal glue, pepsin, dextrin, licorice, or their equivalents may also be present.
Wetting agents such as sodium lauryl sulphate or its equivalent are usually provided.
Where required pH varying agents such as ammonium hydroxide or sulphuric acid are usually added to reach an operating pH.
Certain further solutions require second conductive element complexing agents which preclude precipitation of the second element. These agents were by way of example citric acid, or sodium pyrophosphate, or ethyldiaminetetracetic acid or their equivalents.
A suitable buffer is also provided in certain solutions, where required.
The water is always demineralized.
And for certain applications where the appearance of the product requires an element appearance small quantities of brighteners such as formaldehyde, carbon disulphide, benzene, sulphonic acid or their equivalents may be employed.
In these Examples, unless otherwise indicated the steel matrix was ASA 1018 and the copper was ASTM B-1333 Alloy 110.

Example I

Atlas A151 1020 steel was connected in the apparatus of Fig. 1 as the matrix 14 and a 10% solution of ammonium molybdate in water was placed in reservoir 17.
The following were the characteristics and conditions of treatment:
^*Determined by measurement across 1 sq. cm. plates spaced apart 1 cm. after a 20 second delay.
The sample of Example I was subject to a thermal corrosion test. 25% sulphuric acid was applied to the surface for 20 minutes at 325°C without any surface penetration.
The solution had the following characteristics:
The Mo⁺⁶ concentration may be varied from 1.5% to 2.5% by weight: the pH from 7.2 to 8.2 and the resistivity from 17-25 ohms cm.

Reaction conditions

In the solution set out in Examples II and III the presence of the ferrous and ferric ions are believed to serve to reduce the Mo⁺⁶ valency state to a lower valency state.
While iron is apparently concurrently transferred as illustrated in Fig. 5 the iron has apparently no material effect on the characteristics of the matrix or the molybdenum.
An examination of the sample with an optical microscope shows a continuous coating of molybdenum free from pitting and with a dark silver colour.
As shown in the table below and Fig. 5 an SEM/EPMA scan across the interface between the matrix and the applied metal, molybdenum is seen to be fused to a depth of at least 4 µm with a surface deposit of approximately 1 pm.
Examination under the optical microscope showed a continuous dark silver surface.
The photomicrograph Fig. 6, shows the deposition of a substantially uniform layer of molybdenum 1 micron thick of uniform density.
As shown in Fig. 7 an SEM/EPMA scan across the interface between the substrate and the applied metal shows molybdenum was present to a depth of at least 10 microns and a molybdenum gradient as set out below in Table.

Example IV

An aqueous solution of the following formulation was prepared:
The solution had the following characteristics:
The W⁺⁶ concentration may vary from 1.6% to 2.5%; the pH may vary from 7.5 to 8.5; and the resistivity may vary from 18 ohms cm to 24 ohms cm.

Reaction conditions

As shown by the photomicrographs Figs. 8 and 9, the sample showed a uniform deposit of tungsten approximately 1 micron thick. An SEM/EPMA scan showed fusion of tungsten on copper to a depth of at least 5.0 microns, as can be seen in the Table below and Fig. 10.

Example V

An aqueous solution of the following formulation was prepared:
The solution had the following characteristics:
The concentration of tungsten may be varied from 1.6% to 2.5% by wt.; the pH from 7.5 to 8.5; and the conductivity from 18.8 ohms cm to 22.8 ohms cm.

Reaction conditions

An inspection of the sample by SEM/EPMA, Fig. 11, showed a deposit of tungsten of approximately 0.5 µm and as evident from Fig. 12 and the Table below tungsten was detected at a depth of at least 3 µm.

Example VI

An aqueous solution of the following formulation was prepared:
The solution had the following characteristics:
The Indium concentration may vary from 0.2% to 2.2%; the pH from 1.60 to 1.68; and the resistivity from 48.8 ohms cm to 54.8 ohms cm.

Reaction conditions

An examination of the sample under the optical microscope and the scanning electron microscope showed a continuous surface free from structural faults as shown in Fig. 13.
As shown in the following Table and Fig. 14 and an SEM/EPMA scan across the interface between the copper matrix and the indium layer showed a deposit of approximately 1 µm and fusion of indium to a depth of at least 4 µm.

Example VII

The solution of Example VI was employed and applied to a steel matrix:

Reaction conditions

As shown in Figs. 15 and 16 an even continuous layer of Indium approximately 1 µm thick was deposited on the surface of the matrix. An SEM/EPMA scan, Fig. 16 across the interface and the Table below indicated fusion to a depth of at least 3 µm:
Fig. 17 shows a solid deposit of nickel of uniform density approximately 1.5 µm thick. As shown in the following Table and Fig. 18 an SEM/EPMA scan across the interface between the matrix and the nickel layer shows nickel to be fused to a depth of at least 4 µm.

Example VIII

An aqueous solution of the following formulation was prepared:
The solution had the following characteristics:
The nickel concentration may vary form 2% to 10%, pH from 3.10 to 3.50; and resistivity from 17 ohms cm to 26 ohms cm.

Reaction conditions

Example IX

The same solution as was formulated for Example VIII was prepared and applied to a steel matrix:

Reaction conditions

As shown in Fig. 19 the nickel layer is continuous and substantially uniform in thickness being about 1.5 µm thick.
As shown in Fig. 20 and in the following Table nickel is shown to be fused to a depth of at least 3 um.

Example X

An aqueous solution of the following formulation was prepared:
This solution had the following characteristics:
The pH may be varied from 3.70 to 11; the concentration of Au⁺³ ions may vary from 0.1% to 0.5% by weight: and the resistivity from 40 ohms cm to 72 ohms cm.

Reaction conditions

Observation with the optical and scanning electron microscope revealed a surface deposition of gold approximately 1.5 µm thick. The deposit was continuous and uniformly dense as shown in Fig. 21.
An SEM/EPMA scan across the interface indicated fusion of gold to a depth of at least 3 µm as shown on the Table below and Fig. 22.

Example XI

An aqueous solution of the same formulation as that of Example X was prepared:

Reaction conditions

Observation with the optical and scanning electron microscope revealed a surface deposition of gold approximately 1.0 pm thick. The deposit was uniformly thick and dense as shown in Fig. 23.
An SEM/EPMA scan across the interface indicated fusion of gold to a depth of at least 4.0 µm as shown on the table below and Fig. 24.

Example XII

An aqueous solution of the following formulation was prepared:
This solution had the following characteristics:
The pH may be varied from 0.6 to 1.0; the concentration of Cr⁺⁶ ions may vary from 3% to 20% by weight; and the resistivity from 11 ohms cm to 14 ohms cm.

Reaction conditions

Observation with the optical and scanning electron microscope revealed a surface deposition of chromium approximately 1 µm thick. The surface of the layer was irregular but the deposit appeared free of faults and was continuous as shown in Fig. 25.
An SEM/EPMA scan across the interface indicated fusion of chromium to a depth of at least 3.0 µm as shown on the table below and Fig. 26.

Example XIII

An aqueous solution of the same formulation as employed in Example XII was prepared:

Reaction conditions

Observation with the optical and scanning electrode microscope revealed a surrace deposition of chromium approximately 3.0 µm thick. This is as shown in Fig. 27.
An SEM/EPMA scan across the interface indicated fusion of chromium to a depth of at least 5.0 ₁₁m as shown on the table below and Fig. 28.

Example XIV

An aqueous solution of the following formulation was prepared:
This solution had the following characteristics:
The pH may be varied from 2.5 to 3.5; the concentration of Cr⁺³ ions may vary from 1.8% to 5% by weight; and the resistivity from 16 ohms cm to 20 ohms cm.

Reaction conditions

Observation with the optical and scanning electron microscope revealed a surface deposition of chromium approximately 0.5 µm thick. The deposit was solid and continuous as shown in Figs. 29 and 29A.
An SEM/EPMA scan across the interface indicated fusion of chromium to a depth of at least 3.0 µm as shown on the Table below and Fig. 30.

Example XV

An aqueous solution of the same formulation as prepared for Example XIV was employed:

Reaction conditions

Observation with the optical and scanning electron microscope revealed a surface deposition of chromium approximately 1.0 ₁₁m thick. The surface of the deposit appeared slightly irregular but the deposit was solid and free of faults as shown in Figs. 31 and 31A.
An SEM/EPMA scan across the interface indicated fusion of chromium to a depth of at least 3.0 µm as shown on the table below and Fig. 32.

Example XVI

An aqueous solution of the following formulation was prepared:
This solution had the following characteristics:
The pH may be varied from 10 to 10.2; the concentration of Cd⁺² ions may vary from 0.2% to 0.5% by weight; and the resistivity from 28 ohms cm to 35 ohms cm.

Reaction conditions

In this Example the solution employed was initially as set out above, applied in accordance with the conditions identified as (1). A second solution; that set forth in Example XVII was then applied under the conditions identified as (2). Observation with the optical and scanning electron microscope revealed a surface deposition of cadmium approximately 4 µm thick. This deposit was not homogeneous as shown in Fig. 33 but an SEM/EPMA scan across the interface indicated fusion of cadmium to a depth of at least 9 µm as shown on the Table below and Fig. 34.

Example XVII

An aqueous solution of the following formulation was prepared:
This solution had the following characteristics:
The pH may be varied from 3.2 to 3.5; the concentration of Cd⁺² ions may vary from 1 % to 4% by weight; and the resistivity from 45 ohms cm to 55 ohms cm.

Reaction conditions

Observation with the optical and scanning electron microscope revealed a surface deposition of cadmium approximately 1 µm thick. The surface of the deposit was irregular but it was solid and continuous as seen from Fig. 35.
An SEM/EPMA scan across the interface indicated fusion of cadmium to a depth of at least 4 ₁₁m as shown on the Table below and Fig. 36.

Example XVIII

An aqueous solution of the following formulation was prepared:
This solution had the following characteristics:
The pH may be varied from 11.2 to 12.7; the concentration of Sn⁺² ions may vary from 2% to 5% by weight; and the resistivity from 6.2 ohms cm to 10.3 ohms cm.

Reaction conditions

Observation with the optical and scanning electron microscope revealed a surface deposition of tin approximately 1.2 ₁₁m thick. The deposit was uniformly thick and homogeneous. This is shown in Fig. 37.
An SEM/EPMA scan across the interface indicated fusion of tin to a depth of at least 4 µm as shown on the table below and Fig. 38.

Example XIX

An aqueous solution of the following formulation was prepared:
This solution had the following characteristics:
The pH may be varied from 9 to 9.7; the concentration of Sn⁺² ions may vary from 0.4% to 1% by weight; and the resistivity from 30 ohms cm to 36 ohms cm.

Reaction conditions

Observation with the optical and scanning electron microscope revealed a surface deposition of tin approximately 4 µm thick. This deposit appears to comprise a lower uniform and substantially homogeneous layer of approximately 1 µm thick and an outer slightly porous layer approximately 3 µm thick as shown in Fig. 39.
An SEM/EPMA scan across the interface indicated fusion of tin to a depth of at least 5 µm as shown on the Table below and Fig. 40.

Example XX

An aqueous solution of the same as prepared in Example XIX was employed:

Reaction conditions

Observation with the optical and scanning electron microscope revealed a surface deposition of tin exceeding 2 µm thick. This layer was porous but continuous as shown in Fig. 41.
As SEM/EPMA scan across the interface indicated fusion of tin to a depth of at least 2 µm as shown on the table below and Fig. 42.

Example XXI

An aqueous solution of the following formulation was prepared:
This solution had the following characteristics:
The pH may be varied from 4.5 to 6.5; the concentration of Co+2 ions may vary from 2% to 6% by weight; and the resistivity from 25 ohms cm to 30 ohms cm.

Reaction conditions

Observation with the optical and scanning electron microscope revealed a surface deposition of cobalt approximately 6.5 ₁₁m thick. This layer was uniform and continuous as shown in Fig. 43.
An SEM/EPMA scan across the interface indicated fusion of cobalt to a depth of at least 20 µm as shown on the Table below and Fig. 44.
It was evident by visual inspection and from the previous experiments that the deposit of cobalt was above the 10 pm level was extremely dense.

Example XXII

An aqueous solution of the following formulation was prepared:
This solution had the following characteristics:
The pH may be varied from 11.2 to 11.7; the concentration of Ag⁺¹ ions may vary from 1% to 3% by weight; and the resistivity from 8 ohms cm to 13 ohms cm.

Reaction conditions

Observation with the optical and scanning electron microscope revealed a surface deposition of silver approximately 5 µm thick. The structure is shown in Figs. 45 and 45A.
An SEM/EPMA scan across the interface indicated fusion of silver to a depth of at least 3 µm as shown on the Table below and Fig. 46.

Example XXIII

An aqueous solution of the following formulation was prepared:
This solution had the following characteristics:
The pH may be varied from 1.5 to 2; the concentration of Ag⁺¹ ions may vary from 0.5% to 2.5% by weight; and the resistivity from 6 ohms cm to 12 ohms cm.

Reaction conditions

Observation with the optical and scanning electron microscope revealed a surface deposition of silver approximately 2 11m thick. The structure was as shown in Fig. 47.
An SEM/EPMA scan across the interface indicated fusion of silver to a depth of at least 2.00 11m as shown on the Table below and Fig. 48.
From the foregoing Examples it will be seen that the present application discloses a novel process, apparatus for carrying out the process, solutions for use in the process, and new products which are capable of a wide variety of applications and uses.
It is also to be noted that while the description has been with respect to Examples in which the application was across the entire surfaces it is quite evident that the application may be limited to specific areas of surfaces depending to give a specific desired result.
For example tin, gold and silver, with their inherent excellent conductivity characteristics may be employed in electrical applications and circuits may be fused on other substrates.
The anti-corrosion characteristics of tin, gold, silver, nickel, chromium, cadmium, molybdenum and tungsten are also useful. And the application of those metals to ferrous or non-ferrous substrates will enhance their anti-corrosion behaviour.
Chromium, nickel, silver, gold or tin have the capability of imparting an elegant appearance to the matrix. Chromium, molybdenum, tungsten, titanium and cobalt impart a surface hardness to the matrix.
Indium imparts strength to the matrix, and also serves as anti-galling agent. A molybdenum treated ferrous or non-ferrous matrix has improved friction-wear and high temperature resistance characteristics. It is also useful as a dielectric coating.
A cadmium fused matrix as well as having enhanced corrosion resistance characteristics can also serve as an anti-fouling agent for ship bull treatment.
Silver fused matrices are all useful as a reflecting medium.
It will be apparent that the process and apparatus are extremely facile to use without large capital expenditure and plant and permit the use of materials in applications which were not heretofore contemplated at less expense than previously and apart from the applications and uses specified many others will be apparent to those skilled in the art.

Claims

1. A process for the fusion at ambient temperature of about 20°C of at least one second conductive element comprising ferrous and non-ferrous metals or an alloy thereof, present in a dissociable form as part of a solution, into a matrix of a first conductive element comprising the steps of:

(a) placing the solution having a resistivity of in the range of 5 to 500 ohms cm in contact with a selected limited area of the adjacent surface of said first conductive element comprising ferrous and non-ferrous metals or an alloy thereof;

(b) applying an interrupted half-wave electrical pulsing signal in the range of 2.5 microseconds to 28.6 nanoseconds with a frequency in the range of 400 Hz to 35 MHz to said solution and said first conductive element, said signal being applied having an amplitude of 3 amps per 0.3 square mm whereby said second conductive element is fused with said first conductive element in said selected area without substantial generation of heat to a depth of more than 0.5 11m thickness.

2. A process as claimed in Claim 1 characterised in that said solution comprises: 0.10 to 10% by weight of a first compound including said second metal in a dissociable form;

at least one of a stabilising complexing agent which maintains the first compound in solution and an organic catalyzer for promoting the speed of reaction; and

a solvent chosen from the group comprising water, an organic solvent or a mixture thereof.

3. A process as claimed in any of the preceding claims, characterised in that said aqueous solution has a pH in the range of 0.4 to 14.

4. A process as claimed in any of claims 1 to 3 wherein said second conductive element is chosen from the elements of groups 1b, 2b, 3b and 4b, and said first conductive element is chosen from the group comprising ferrous or non-ferrous metals or an alloy thereof.