Method of treating ceramics for use as tips in saws and other tools or other structures

A method of processing a ceramic body, such as a saw tip so that the ceramic body can be bonded to a substrate, such as a saw blade. The ceramic body is desirably a cermet, and it is first cleaned, preferably using sodium hydroxide. After this, the ceramic body is etched by an acid, after which a metallic coating is applied to the bonding surface either by electrolysis by an electroless process. Then the ceramic body is either brazed or welded to the substrate.

BACKGROUND OF THE INVENTION
 a) Field of the Invention
 This invention relates to a method of brazing or welding a ceramic body,
 such as a saw tip or other object, to a substrate such as a saw blade tip.
 The present invention also relates to the ceramic body itself which is
 processed in a particular manner so that it can be brazed or welded to a
 substrate, and also to an article made up of such a ceramic body joined to
 a substrate.
 b) Background Art
 Ceramics have attributes such as high wear and corrosion resistance as well
 as stability at high temperature that make their use desirable in
 applications such as saws, tools and jet engine exhausts, and in other
 applications where similar conditions exist.
 The very qualities that make ceramics desirable for use in these
 applications also make them very hard to use. Resistance to wear, heat and
 corrosion make them very difficult to braze or weld successfully.
 Currently it is possible to braze ceramics using special alloys in special
 atmospheres and with elaborate preparation. Preparing ceramics for plating
 and brazing is well known in industries such as electronics and aerospace.
 The drawbacks have been that the special atmospheres and special alloys
 also made the joining very expensive in terms of materials, quipment and
 overall processing costs. In addition the epoxies and alloys suitable for
 brazing ceramics are typically too weak and break down at temperatures too
 low to make their use, practical in many applications. Active metal
 alloys, catalytic surface treatment, special atmospheres and multi-step
 processing all add to the cost of the processing in an extremely price
 sensitive industry.
 Brazing is commonly defined as a process for joining two dissimilar
 materials at a temperature in the range of, or above, 800.degree. F. The
 brazing alloys which are commonly used are silver based because of their
 strength, impact resistance and corrosion resistance, and quite commonly
 in the temperatures in the range 1150.degree. F. to 1350.degree. F. are
 employed in the brazing process. The brazing can be accomplished by
 various heating means, such as utilizing oxyacetylene, induction brazing
 or resistance brazing. It is also possible that could be accomplished in
 an oven, or with plasma. The more common methods are simply to use an
 oxyacetylene torch or induction brazing.
 Another process of joining two metals together is called welding where the
 two metal objects are placed in contact with one another without the use
 of a separate brazing alloy, and heat is applied so that the two metals
 flow together and upon cooling become joined to one another.
 One application of brazing in connection with a ceramic like material is
 brazing tungsten carbide saw tips to a circular saw blade. The saw blade
 is made of a high quality steel, and plurality of notches are formed in
 the perimeter of the saw blade. The tungsten carbide tips are formed in
 the desired configuration, with these tips have a bonding surface matching
 the configuration of the notches in the saw blade.
 The bonding surfaces of the notches in the saw blade and of the tips are
 properly prepared to remove contaminants, and a brazing compound is
 applied to the bonding surface of the tips.
 The tips are placed in the notches of the saw blade, and heat is applied.
 The assembly of the saw blade with the tips is permitted to cool, to form
 a completed circular saw with the tips securely joined to the saw blade.
 When the welding process is employed, the brazing compound is not used. In
 other respects, the welding process is similar to the brazing process.
 The tungsten carbide tips are quite durable and are able to withstand
 relatively high temperatures. Thus, for high quality saws that need to
 operate in more severe environments (higher temperature, vibration,
 impacts, etc.), tungsten carbide tips have commonly been used.
 It has long been recognized that saw tips made of cermet have certain
 qualities which surpass those of tungsten carbide. First, cermets are
 highly resistant to various corrosive materials. This makes use of cermets
 quite desirable when the saw blades are commonly used to cut cedar,
 spruce, hemlock and other green lumber, since these types of wood have
 acids that can corrode the saw blade, the saw tips and the bonding
 material. Further, a cermet saw tip, made (for example) from titanium
 carbonitride is able to maintain a sharper edge for as much as three times
 as long or longer than a comparable tungsten carbide saw tip. Also, a tip
 made of titanium carbonitride tip is able to withstand higher
 temperatures, and maintain a sharp edge.
 However, in general it has not been possible to achieve the benefits which
 could be achieved by using saw tips made from a cermet material, mainly
 because of the difficulty of reliably bonding the cermet to the saw blade.
 In general the epoxies and alloys which are more suitable for brazing
 ceramics or cermets are too weak and also break down at temperatures too
 low to make them commercially practical for many applications.
 Thus, when ceramics (including cermets) have been used, it is commonly in
 indexable or mechanically held applications in tools. For example, they
 can be used in a rotary cutting tool where the cutter inserts are placed
 in a pocket at the perimeter of the tool and mechanically held in place.
 However, to the best knowledge of the applicants, it has not been found to
 be commercially practicable to employ cermets where they must be brased or
 otherwise bonded to the saw blade or other substrate.
 SUMMARY OF THE INVENTION
 It is an object of the present invention to provide a commercially feasible
 process for joining ceramic parts to a substrate in a commercially viable
 manner so that the process has a desirable balance of advantageous
 features, such as, high bond strength at high temperatures, resistance to
 hostile environments (e.g. contact with corrosive materials, to high
 impact, subject to residual stresses and vibration, etc.), low cost, being
 able to accomplish the process rapidly and simply, and being an
 environmentally desirable process. The present invention uses chemicals
 which are more commonly available, allows for brazing using standard
 alloys, and also using these at ambient temperatures.
 It is a further object to provide a process whereby ceramics can be
 prepared so that high temperature/high strength/low cost alloys (such as
 silver and copper based alloys) can be used easily and well, thus allowing
 their use in applications such as cutting tools, wear parts and high
 temperature linings such as in jet engine exhausts.
 In the method of the present invention, the ceramic body is provided so as
 to have a clean surface which is substantially free of contaminants. This
 is followed by an etching step where the bonding surface of the ceramic
 body is etched. Then there is applied to this ceramic bonding surface a
 coating of a metallic material capable of being applied as a surface layer
 to the ceramic bonding surface and being bonded to this ceramic bonding
 surface. Then bonding is accomplished by either of two ways, namely;
 i) placing the bonding surfaces of the ceramic body and the substrate
 against one another with the brazing material therebetween and bonding
 these to one another by a bonding process, or
 ii) placing the bonding surfaces of the ceramic body and the substrate
 against one another and bonding these to one another by a welding process.
 The cleaning step is desirably accomplished by electro cleaning. More
 specifically, the ceramic body is immersed in an electrolytic solution,
 and the ceramic body is connected one of two electrodes in the
 electrolytic solution. A current is passed between the electrodes. The
 electrolytic solution is desirably an alkaline solution which comprises,
 at least in part, sodium hydroxide, potassium hydroxide, or combinations
 thereof.
 The etching is accomplished by an etching agent which comprises primarily
 an inorganic acid or a combination of inorganic acids. More specifically,
 the etching agent is selected from a group consisting of hydrochloric
 acid, hydrofluoric acid, sulfuric acid, nitric acid, and combinations of
 these.
 The metallic coating material comprises, at least in part, a metal that is
 selected from a group comprising cobalt, copper, nickel, zinc, silver, and
 combinations thereof. In the preferred form, the application of the
 metallic coating is accomplished by electrolysis, and the electrolyte for
 the electrolytic deposition is selected from a group comprising; ammonium
 cobalt chloride, cobalt chloride, cobalt sulfate, nickel sulfate, ammonium
 nickel sulfate, a zinc based solution, a cobalt based solution, a nickel
 based solution, and combinations thereof.
 Alternatively, the application of the metallic coating can be accomplished
 by an electroless process.
 Preferably the ceramic body comprises a metal based ceramic, and more
 particularly a cermet. The cermet body may comprise:
 i) titanium, aluminum, tungsten, silicon, and/or combinations thereof; and
 ii) carbon, nitrogen, oxygen and/or combinations thereof. A preferred
 composition of the ceramic body is one that comprises titanium, aluminum,
 and/or combinations thereof. More specifically, the ceramic body comprises
 titanium carbide, tungsten carbide, titanium carbonitride, titanium
 nitride, aluminum oxide, and/or combinations thereof.
 Desirably after the application of the coating of a metallic material, the
 ceramic bonding surface is treated with a passivation solution comprising
 an acid. The acid in the preferred form comprises hydrochloric acid,
 sulfuric acid, and combinations thereof.
 In a preferred embodiment, the ceramic body is a saw tip and the substrate
 is a saw blade. Also, the present invention can be used where the ceramic
 body is used in tools, such as drills, routers, shapers and similar
 applications; in high stress applications such as wear parts and scrapers;
 and in high temperature applications such as ovens, kilns, and jet
 exhaust; and in cotton gins. Further, the invention comprises a bonded
 structure made up of the ceramic body and the substrate, which has been
 joined in according with the process of the present invention. This
 structure can be bonded either by a bonding process, or by a welding
 process.
 The present invention also comprises a ceramic body which has been process
 in accordance with the steps of the present invention, after which the
 ceramic body can be used by bonding it to a substrate as described above.
 Other features of the present invention will become apparent from the
 following detailed description.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 The present invention will be described specifically as it applies to the
 brazing or welding of ceramic (more specifically cermet) saw tips to a saw
 blade. However, within the broader scope of the present invention, it will
 be recognized that the present invention could also be applicable to other
 applications, and particularly applications which have more stringent
 operating environments where the present application would be particularly
 advantageous (e.g. tools, such as drills, routers, shapers and other
 similar tools; wear parts and scrapers in high stress application; cotton
 gins; ovens, kilns, jet exhausts and other similar structures).
 With reference to FIG. 1, there is shown a perimeter portion of a saw blade
 10 having a plurality of tooth sections 12, with each tooth section being
 formed with a notch 14 with a bonding surface 16. For each tooth section
 12 there is a saw tip 18 with a cutting edge 20 and a bonding surface 22
 matching the bonding surface 16 of the saw tooth. The tips 18 are
 positioned in the notches and the bonding surfaces of the tips 18 and the
 notches are bonded to one another.
 In general the ceramic body (in this specific disclosure the saw tip) is
 made of a ceramic material (more desirably a cermet) and is formed in the
 desired shape (i.e. as a saw tip) by conventional manufacturing
 techniques. The saw tip is cleaned (e.g. by immersing the saw tips in a
 cleaning bath), and then etched (e.g. by being placed in a
 cleaning/etching solution). The ceramic tips then have a layer of a
 suitable metallic material placed thereon (desirable by electroplating or
 electroless plating) so that a wettable, brazeable surface is formed
 allowing the use of standard braze alloys, such as AWSB BAg alloys or a
 surface suitable for welding.
 In the preferred form of the present invention, the ceramic material by
 which the saw tip (or other body) is made is a metal based ceramic, such
 as those based on tungsten, titanium, aluminum, silicon and possibly other
 metals, joined with carbon, nitrogen and other similar materials or
 combinations thereof, such as TiCN, WC, TiCN (also as TiC/TiN) Al.sub.2
 O.sub.3 Si.sub.3 N.sub.4, SiC and others. The steps of the process can be
 summarized as follows.
 The overall process of the present invention for preparing the ceramic body
 is as follows:
 1. The part is thoroughly cleaned.
 2. The part is then treated in such a manner as to prepare the surface to
 bond with an intermediate material. Typically this is a chemical bath and
 may or may not use electric current. The surface is roughened and
 chemically activated.
 3. The surface is then plated with a metal or other material that will bond
 to the ceramic as well as forming a layer suitable for brazing with
 standard alloys or welding. Typically this is also done in a chemical bath
 and may or may not use electric current.
 4. If needed, the part may be cleaned or otherwise passivated if desired.
 Then to carry the invention further to complete the bonding of the ceramic
 body to the substrate, the above steps are followed by a welding or
 brazing step.
 Best Mode for Carrying Out The Invention
 In a preferred form of the invention a ceramic part such as a cermet or
 titanium carbonitride is preferred for use as a saw tip.
 Step 1 Cleaning
 Purpose: To remove all stains, oil, dust, etc. and to create additional
 roughness on the surface.
 A preferred method of cleaning is a cathodic electro cleaning process in
 alkaline solution as discussed in patent U.S. Pat. No. 5,624,626. The
 ceramic part is connected to the negative terminal of the rectifier and a
 stainless steel rod is used as an anode connected to the positive charge.
 The solution is 15% sodium Hydroxide
 Temperature is 150.degree.-160.degree. F.
 Voltage 5-6 v
 Time 5-7 minutes
 Alternatively the cleaning could be done without electric current. Also
 potassium hydroxide could be used.
 Step 2 Surface Etching
 The part is immersed in a solution for an etching effect. One such solution
 is 20% Hydrochloric acid solution (HCl) or other solution depending on the
 material and other considerations such as cost and safety.
 Temperature--ambient 70.degree.-80.degree. F.
 Time 5 minutes
 This process may be accelerated or enhanced by the use of electric current,
 higher temperature or different combinations of chemicals.
 Step 3 Deposition of Cobalt or Other Metal
 The parts to be treated are connected to the negative side of a rectifier.
 An anode such as stainless steel, cobalt or other appropriate material is
 used.
 A 17.5% solution of Ammonium Cobalt Sulfate (NH.sub.4).sub.2
 Co(SO.sub.4).sub.2 in water is used. Other cobalt compounds, such a Cobalt
 Chloride and Cobalt Sulfate, maybe used and compounds based on other
 metals such as Titanium may also be used.
 Temperature--ambient 70.degree.-80.degree. F.
 Current density 5-15 amp/sq. Ft.
 pH 5 to 5.5
 Time is a variable depending on the thickness of coating desired and the
 number and size of the parts.
 The elapsed time that the Ceramic body is treated to the electrical
 potential difference should be sufficient to pre-treat the ceramic body
 for use in the method of the present invention. The preferred elapsed time
 may vary depending upon the composition of the ceramic body, the magnitude
 of the electrical potential difference, and the composition of the
 solution in the bath. However, for most applications, the elapsed time in
 which the electrical potential difference is imposed across the
 electrolytic cell may be between about one (1) minute and about five (5)
 minutes. In a more preferred form of the invention, the elapsed time is
 between about two (2) minutes and about three (3) minutes.
 The preferred electrical potential difference may vary depending upon the
 composition of the ceramic body the amount of time that the ceramic body
 is in the bath, and the composition of the solution in the bath. However,
 for most applications, the difference in electrical potential imposed
 across the electrolytic cell may be between about two (2) volts and about
 fifteen (15) volts. In a more preferred form of the invention, the
 difference in electrical potential is between about five(5) volts and
 about ten (10) volts. And, in an even more preferred form of the
 invention, the electrical potential difference is about six (6) volts.
 Cobalt or other appropriate anode may be used to replenish the bath.
 Step 4 Post Cleaning of the Parts
 The parts are desirably post cleaned by dipping in a solution such as 20%
 HCl for 30 to 60 seconds.
 Once this process is performed the parts may then be brazed on saws using
 standard braze alloys and will work successfully in sawing and other
 applications. Alternatively, a welding process could be used.
 The method of the present invention is particularly useful for treating a
 ceramic body, such as a Titanium Carbonitride (cermet) to provide a
 surface on the ceramic body, which is wettable by a silver brazing alloy.
 When silver brazing alloy is applied to the surface of an untreated
 ceramic body, the brazing alloy forms a globule on the surface instead of
 flowing evenly and completely across the surface. Joints formed by a
 globule of alloy are generally not as uniformly strong for most industrial
 applications, such as adhering tips to a circular saw plate. The present
 invention provides a treated surface on a ceramic saw tip, which is
 readily wettable by a silver brazing alloy compound. The brazing compound
 flows evenly and completely across the surface of the tip such that a
 uniformly strong joint is formed between the ceramic tip and the circular
 saw plate. In addition, a body treated according to the method of the
 present invention remains clean and wetable such that the body may be
 stored and processed at a later time.
 With regard to the ceramic materials which are to be bonded to a substrate,
 within the very broad scope of the present invention, it is conceivable
 that a wide variety of such ceramic materials would be found suitable. In
 general, the ceramics which are metal based ceramics are believed to be in
 general better adapted for use in the present invention. Titanium,
 aluminum, tungsten, and/or silicon and combinations thereof in combination
 with carbon, nitrogen, oxygen and combinations of these would be found
 suitable. Further, ceramics based on titanium, aluminum and combinations
 thereof have been found to work particularly well in the present
 invention. Specific examples of these are titanium carbonitride, titanium
 carbide, and also aluminum oxide enriched with titanium carbide. It would
 also be possible to use combinations of the these and also to add other
 ingredients thereto.
 As indicated previously, a first step in the present invention is properly
 cleaning the surface of the ceramic body. It is conceivable that the
 ceramic body would be provided with the bonding surface thereof freshly
 cleaned and ready for use, in which case the first step of the present
 invention would be simply providing such cleaned ceramic pieces. However,
 this is usually not the case.
 As indicated previously, the preferred method of cleaning is use of an
 alkaline solution as described in U.S. Pat. No. 5,624,626. Within the
 broader scope of the present invention, other cleaning methods and
 possibly cleaning along with accomplishing other benefits such as
 activating the surface, possibly pitting the surface somewhat, or
 otherwise chemically treating the surface could be used. Further, such
 steps as degreasing, possibly with trichlorides could be used, in
 combination with rinses (e.g. with an alcohol rinse ). The usual
 contaminants would be dirt, oil and greases which should be removed and
 also the oxides should be removed as much as possible.
 With regard to etching this step requires the correct acid or combination
 of acids for the material in the right concentrations for the correct
 time. As the concentration of acid drops below a practical working limit
 of approximately 5%, the time required can become so long that it is not
 suitable industrially.
 In general, organic acids have not been found to be suitable. The acids
 which have worked best are hydrochloric acid, hydrofluoric acid, sulfuric
 acid and combinations of the same. Also, in some instances nitric acid is
 used in combination with hydrochloric and/or hydrofluoric acid. Also, some
 acids work well with particular cermets than others. For example,
 hydrochloric acid or sulfuric acid will etch the surface of titanium
 carbonitride. Superior results may be obtained by the two in combination.
 These acids will not effect titanium carbide. Titanium carbide etches with
 a combination of hydrofluoric and nitric acids. Either acid alone will
 have little or a weak effect. For etching aluminum oxide, hydrofluoric or
 a combination of hydrofluoric and hydrochloric acid has been found
 suitable.
 The acid bath works well at room temperature and when slightly warm. As the
 acid gets too hot it creates hazards, which makes its use in industrial
 applications undesirable.
 With regard to the application of the metallic coating material, cobalt has
 been found to be particularly effective, and nickel, zinc, copper and
 silver could also be used, as well as combinations of these metals.
 The preferred method of application of the metallic coating material is by
 electroplating, as described above. Also, the ceramic part could simply be
 plated by an electroless process.
 When cobalt is used as the metallic coating material with electrolysis,
 various solutions could be used, such as ammonium cobalt sulfate, cobalt
 chloride or combinations thereof. If nickel is used as the metallic
 coating material, then the plating solution could be nickel sulfate,
 ammonium nickel sulfate, combinations thereof or other such compounds.
 EXAMPLE 1
 Step One--Cleaning
 Twenty saw tips composed of TiCN (titanium carbonitride ceramic) for use on
 a circular saw plate are obtained. Upon visual inspection, the surfaces of
 the tips are relatively free of pitting and include some contaminants,
 such as carbonized oils, free carbon, iron oxide, general dust, shop
 contaminats and metal particles. The saw tips are immersed in a bath of a
 15 percent by volume sodium hydroxide solution and connected as a cathode
 in an electrolytic cell. Stainless steel is connected as an anode. The
 sodium hydroxide bath is maintained at room temperature, approximately
 70-80 degree(s) F. Six (6) volts are imposed across the electrolytic cell
 for two (2) minutes. The tips are removed from the bath. Upon microscopic
 inspection (1000.times.), the surface is clean but smooth and relatively
 unpitted. In addition, the surfaces of the tips are substantially free of
 contaminants.
 Step 2 Surface Etching
 The part is immersed in a solution for an etching effect. One such solution
 is 20% Hydrochloric acid solution (HCl) solution or other depending on the
 material and other considerations such as cost and safety.
 Temperature--ambient 70.degree.-80.degree. F.
 Time 5 minutes
 This process may be accelerated or enhanced by the use of electric current,
 higher temperature or different combinations of chemicals.
 Step 3 Deposition of Cobalt or Other Metal
 The parts to be treated are connected to the negative side of the
 rectifier. An anode such as stainless steel is used.
 A 17.5% solution of Ammonium Cobalt Sulfate (NH.sub.4).sub.2
 Co(SO.sub.4).sub.2 in water is used. Other cobalt compounds, such a Cobalt
 Chloride and Cobalt Sulfate, may be used and compounds based on other
 metals such as Titanium may also be used.
 Temperature--ambient 70.degree.-80.degree. F.
 Current density of 5-150 amps/sq. ft. depending on the solution with 5-15
 amps being most common.
 pH 5 to 5.5
 Time is a variable depending on the thickness of coating desired and the
 number and size of the parts.
 Cobalt or other appropriate anode may be used to replenish the bath,
 Step 4 Post Cleaning of the Parts
 The parts may be post cleaned by dipping in a solution such as 20% HCl for
 30 to 60 seconds.
 Once this process is performed that parts may then be brazed on saws using
 standard braze alloys and will work successfully in sawing and other
 applications.
 EXAMPLE 2
 Example 1 is repeated except the material is Titanium Carbide and the
 etchant is Nitric acid, Hydrofluoric acid and water in a 1:1:1 ratio.
 EXAMPLE 3
 Example 1 is repeated except the material is Alumina with a Titanium
 Carbide addition and the etchant is Nitric acid, Hydrofluoric acid and
 water in a 1:1:1 ratio.
 EXAMPLE 4
 Examples 1,2 & 3 are repeated except the plating solution is Cobalt
 Chloride.
 EXAMPLE 5
 Examples 1,2 & 3 are repeated except the plating solution is Cobalt
 Sulfate.
 EXAMPLE 6
 Examples 1,2 & 3 are repeated except the plating solution is Nickel
 Sulfate.
 EXAMPLE 7
 Examples 1,2 & 3 are repeated except the plating solution is Ammonium
 Nickel Sulfate.
 EXAMPLE 8
 Examples 1,2 & 3 are repeated except the plating solution is Zinc based.
 EXAMPLE 9
 Examples 1,2 & 3 are repeated except the plating solution is based on other
 metals.
 EXAMPLE 10
 Examples 1,2 & 3 are repeated except the plating process is electroless.
 EXAMPLE 11
 The tips from Examples 1-10 are rinsed in water and allowed to air dry.
 Then, silver solder is applied to a surface of each tip. The solder flows
 smoothly across the surface to cover the surface. The saw tips are adhered
 by the solder to a circular saw plate. The joint between each saw tip and
 the circular saw plate is strong. Upon visual inspection two weeks after
 the tips have been treated according to the method of the present
 invention, the tips have not discolored. Upon impact testing the steel saw
 body will rip or the ceramic will rupture before the braze joint fails.
 EXAMPLE 12
 For purposes of comparison, examples 1-10 are repeated, eliminating the
 first cleaning process. Then, silver solder is applied to a surface of
 each tip. The silver solder flows across the surface of the tips, but
 without complete coverage. The saw tips are adhered by the solder to the
 circular saw plate. The joint between each saw tip and the circular saw
 plate is somewhat strong, but much weaker than the joint in Example 11.
 Upon visual inspection two weeks after the tips have been treated
 according to the method of the present invention, the tips have not
 discolored.
 EXAMPLE 13
 Also for purposes of comparison, examples 1-10 are repeated, eliminating
 the etching process. Then, silver solder is applied to a surface of each
 tip. The silver solder flows across the surface of the tips, but without
 complete coverage. The saw tips are adhered by the solder to the circular
 saw plate. The joint between each saw tip and the circular saw plate is
 somewhat strong, but not as strong as the joint in Example 11. Upon visual
 inspection two weeks after the tips have been treated according to the
 method of the present invention, the tips have not discolored.
 EXAMPLE 14
 Again for purposes of comparison examples 1-10 are repeated, eliminating
 the plating process. Then, silver solder is applied to a surface of each
 tip. The silver solder flows across the surface of the tips, but without
 complete coverage. There is most typically a balling of the braze alloy
 and the ball may be removed with finger pressure. If the saw tips are
 brazed to the steel plate, the joint between each saw tip and the circular
 saw plate is somewhat strong, but not as strong as the joint in Example
 11. The joint is usually strong enough to hold the tips to the steel body
 if no force is applied. The tips typically fall off in shipping or may be
 plucked off by hand. In all cases the tips are readily "shucked off" as
 soon as any cutting is attempted. Upon visual inspection two weeks after
 the tips have been treated according to the method of the present
 invention, the tips have not discolored.
 EXAMPLE 15
 Examples 1-10 are repeated with three (3) volts imposed across the
 electrolytic cell for three (3) minutes in the plating step set forth.
 Then, silver solder is applied to a surface of each tip. The solder flows
 smoothly across the surface to cover the surface. The saw tips are adhered
 by the solder tote circular saw plate. The joint between each saw tip and
 the circular saw plate is strong. Upon visual inspection two weeks after
 the tips have been treated according to the method of the present
 invention; the tips have not discolored.
 EXAMPLE 16
 Examples 1-10 are repeated with a 10 percent by volume etchant solution
 used. Then, silver solder is applied to a surface of each tip. The solder
 flows smoothly across the surface to cover the surface. The saw tips are
 adhered by the solder to the circular saw plate. The joint between each
 saw tip and the circular saw plate is strong. Upon visual inspection two
 weeks after the tips have been treated according to the method of the
 present invention, the tips have not discolored.
 EXAMPLE 17
 Examples 1-10 are repeated. Two weeks later, silver solder is applied to a
 surface of each tip. The solder flows smoothly across the surface to cover
 the surface. The saw tips are adhered by the solder to the circular saw
 plate. The joint between each saw tip and the circular saw plate is
 strong. In addition, the tips have not discolored.
 EXAMPLE 18
 For purposes of comparison, twenty saw tips composed of ceramic (Titanium
 Carbonitride TiCN) for use on a circular saw plate are obtained. Upon
 microscopic inspection, the surfaces of the tips are relatively free of
 pitting and include some contaminants, such as carbonized oils, free
 carbon, iron oxide, and metal particles. Silver solder is applied to a
 surface of each saw tip. The solder does not flow smoothly across the
 surface of each saw tip, but instead a globule of solder is formed on each
 saw tip. The saw tips are adhered by the solder to the circular saw plate.
 Some of the joints between the saw tips and the circular saw plate are
 weaker than the joints formed with the tips treated according to the
 method of the present invention.
 When the untreated tips were processed in accordance with the present
 invention brazed on a saw they fell off during shipping to the test site.
 The treated tips brazed with a strong joint so that impact testing
 destroyed either the saw tip or ripped the steel saw plate but the braze
 joints did not fail.
 EXAMPLE 19
 Saw tips are prepared as in steps one through ten. Then silver braze alloy
 is not applied. Instead, the saw tips are welded to the steel saw body
 without braze alloy.
 The plated parts are placed in contact with the steel saw body and then
 they are heated using induction heating, a torch, resistance heating or
 other method common to the industry. The plating on the saw tips and the
 saw body flow together and for a join by a process commonly known as
 welding in the industry.