Ceramics can be metallized for brazing by a plating process. A ceramic such as Alumina is plated with a metal and then the part can be brazed with common braze alloys and techniques as simple as an oxy-acetylene torch.  

Originally the thinking was that Titanium is beneficial in active braze alloys so it might be possible to work with material containing Titanium using standard brazing methods. This technique is currently used on Titanium Carbonitride and similar Titanium based materials. It also works well on materials that contain titanium such as grades of alumina with TiC added.

Because ceramics are so tightly bonded you do not need to effect much of the material to get a strong bond. Whatever you can attach to on the surface will serve as a solid anchor for the rest of the part. This has lead to directly effecting Alumina and Silicon as in Silicon Nitride.

Ceramics once regarded as non reactive can be made slightly reactive by the use of strong acids and a great deal of electrical energy applied in a manner consistent with standard electroplating tools and techniques.

Left – As purchased, 2nd left – brazed as purchased, 3^rd left – treated, Right – treated & brazed

 Brazed Alumina

Incredible performance

Ø      This part can braze with a tensile strength up to 90,000 psi.

Ø      T is suitable for use with temperatures up to 12200 F.

Ø      The High Impact alloy makes it suitable for use in impact situations such as saws.

Ø      Low cost – The cost of pretinning can be well under a dollar.  Pretinning is the application of the braze alloy to one part before joining.

These four parts show the effects of our surface treatment process.

The left part is an untreated part as purchased from a machine shop supply house.  The second part is an untreated part we tried to braze.  The braze alloy formed a nice sphere in the middle of the part.  There was to part wetting.  The third part has been treated with our surface treatment.  This little dark spot at the top was where the part was held during treatment.  The fourth part shows an insert coated with braze alloy.  The lower edge shows wetting so strong that the capillary action overcame the edge of effect barrier.  In other words, the alloy did not spill over the edge but migrated through the material surface.  The alloy used was Bag-22 AWS silver braze alloy.  It was brazed in an ambient atmosphere furnace using Englehard Black Flux.

The alumina parts used are machining inserts because they are well made and readily available.  They also illustrate the ability of this process to d3eal with currently available commercial products.  The alumina parts are NTK insert DNMG433 ZhC6 reference numbers =HC6DNGN433-TN (5752647).  This is a TiC – Al₂O₃ combination.