Braze alloy containing particulate material

Abstract

A minimum joint thickness can be assured by incorporating beads or particles having a diameter corresponding to the joint thickness desired and which are infusible at the brazing temperature. Preferably such particles are formed of high-melting metals, metal oxides, ceramics, or cermets and are mixed into the alloy paste prior to fusing. In a preferred embodiment, the particle-containing paste is mixed with a non-flux carrier to facilitate application to the elements to be brazed. Exemplary application methods may include painting, rolling, screening, or extrusion dispensing. Brazing alloys in accordance with the invention are useful in bonding ceramics to ceramics, ceramics to metals, and metals to metals.

1 . A brazed joint comprising:
 a) a first element having a first surface;   b) a second element having a second surface; and   c) a braze seal disposed between said first and second surfaces, said seal being formed of a particulated braze alloy and an evanescent non-flux carrier, wherein said seal has a predetermined thickness corresponding to a size of particulates in said particulated braze alloy, and wherein an initial thickness of said particulated braze alloy between said first and second surfaces is greater than said predetermined thickness of said seal.   
   
   
       2 . A joint in accordance with  claim 1  wherein said first element is formed of a metal and said second element is formed of a ceramic. 
   
   
       3 . A joint in accordance with  claim 1  wherein said size is a diameter of said particulates. 
   
   
       4 . A joint in accordance with  claim 1  wherein a shape of said particulates is selected from the group consisting of irregular and spherical. 
   
   
       5 . A joint in accordance with  claim 1  wherein said particulates are selected from the group consisting of metals, metal alloys, ceramics, and cermets. 
   
   
       6 . A joint in accordance with  claim 1  wherein said particulated braze alloy includes silver. 
   
   
       7 . A joint in accordance with  claim 1  wherein said particulated braze alloy includes an element selected from the group consisting of copper and vanadium. 
   
   
       8 . A joint in accordance with  claim 1  wherein said size of said particulates is between about 30 μm and about 50 μm 
   
   
       9 . A joint in accordance with  claim 1  wherein said particulated braze alloy includes at least one metal fusible within a temperature range, wherein said particulates are infusible within said temperature range. 
   
   
       10 . A joint in accordance with  claim 1  wherein said temperature range is between about 900° C. and about 1000° C. 
   
   
       11 . A method of forming a brazed joint comprising:
 providing a first element having a first surface;   providing a second element having a second surface;   providing a particulated slurry including a particulated braze alloy and an evanescent non-flux carrier, said particulated braze alloy including a fusible metal and infusible particulates;   applying said particulated slurry to at least one of said first and second surfaces;   disposing said particulated slurry between said first and second surfaces;   applying a clamping pressure to said first and second surfaces to form a clamped assembly;   heating said clamped assembly above a liquidus temperature of said particulated braze alloy to fuse said fusible metal, drive off said evanescent non-flux carrier, and collapse said braze joint until further collapse is prevented by said infusible particulates contained in said particulated braze alloy.   
   
   
       12 . A method in accordance with  claim 11  wherein said particulated slurry is applied to at least one of said first and second surfaces by at least one of brushing, painting, rolling, spraying, screening, or extrusion dispensing. 
   
   
       13 . A method in accordance with  claim 11  wherein said first element is formed of a metal and said second element is formed of a ceramic. 
   
   
       14 . A method in accordance with  claim 11  wherein a shape of said infusible particulates is selected from the group consisting of irregular and spherical. 
   
   
       15 . A method in accordance with  claim 11  wherein said infusible particulates are selected from the group consisting of metals, metal alloys, ceramics, and cermets. 
   
   
       16 . A method in accordance with  claim 11  wherein said particulated braze alloy includes silver. 
   
   
       17 . A method in accordance with  claim 11  wherein said particulated braze alloy includes an element selected from the group consisting of copper and vanadium. 
   
   
       18 . A method in accordance with  claim 11  wherein a size of said infusible particulates is between about 30 μm and about 50 μm 
   
   
       19 . A method in accordance with  claim 11  wherein said fusible metal is fusible within a temperature range between about 900° C. and about 1000° C., wherein said infusible particulates are infusible within said temperature range.