Process for the low-deformation diffusion welding of ceramic components

Abstract

A process for joining ceramic components, wherein the components which are to be joined consist of sintered nonoxide ceramic, and the components are brought into contact with one another in a diffusion-welding process in the presence of a shielding gas atmosphere and are joined with little deformation, under the application of a temperature of at least 1600° C., preferably over 1800° C., particularly preferably over 2000° C., and if appropriate a load, to form a monolith, the components which are to be joined experiencing plastic deformation in the direction in which force is introduced of less than 5%, preferably less than 1%.

1 . A process for joining ceramic components, wherein the components which are to be joined consist of sintered nonoxide ceramic, and the components are brought into contact with one another in a diffusion-welding process in the presence of a shielding gas atmosphere and are joined with little deformation, under the application of a temperature of at least 1600° C., preferably over 1800° C., particularly preferably over 2000° C., and if appropriate a load, to form a monolith, the components which are to be joined experiencing plastic deformation in the direction in which force is introduced of less than 5%, preferably less than 1%.  
   
   
       2 . The process as claimed in  claim 1 , wherein the diffusion welding used is a hot-pressing process.  
   
   
       3 . The process as claimed in  claim 1 , wherein at least one of the components to be joined consists of a nonoxide ceramic which during the joining process has a creep rate which is always lower than 2·10 −4  1/s, preferably always lower than 8·10 −5  1/s, particularly preferably always lower than 2·10 −5  1/s.  
   
   
       4 . The process as claimed in  claim 1 , wherein at least one of the components to be joined consists of titanium diboride, boron carbide, silicon nitride, silicon carbide or mixtures thereof, particularly preferably of silicon carbide.  
   
   
       5 . The process as claimed in  claim 4 , wherein at least one of the components to be joined consists of coarse-grained sintered silicon carbide with a bimodal grain size distribution and a mean grain size of greater than 5 μm, preferably greater than 20 μm, particularly preferably greater than 50 μm, which may contain up to 35% by volume of other material components, such as graphite, boron carbide or other ceramic particles.  
   
   
       6 . The process as claimed in  claim 1 , which is carried out at a temperature of >1600° C., particularly preferably >1800° C., especially preferably >2000° C., and a load of >10 kPa, preferably >1 MPa, particularly preferably >10 MPa, with the temperature-holding time preferably exceeding a duration of 10 min, particularly preferably 30 min.  
   
   
       7 . A component made from a nonoxide ceramic with a seamless join.  
   
   
       8 . The component as claimed in  claim 7 , which at the seamless join has a bending rupture strength of >150 MPa, particularly preferably >250 MPa, measured using the 4-point method.  
   
   
       9 . The component as claimed in  claim 7 , wherein the bending rupture strength in the region of the seamless join is just as high as in the base material of the component.  
   
   
       10 . The component as claimed in  claim 7 , which is a container, tube, reactor, roll, holder, lining, valve, heat exchanger, heating element, plating, a wearing component, such as a sliding-contact bearing or an axial face seal, a brake, a clutch, a nozzle or a deformation tool.  
   
   
       11 . The use of the component produced by a process as claimed in  claim 1  as a structural component or a functional component, including a container, tube, reactor, lining, valve, heat exchanger, heating element, plating, a wearing component, such as a sliding-contact bearing or axial face seal, a brake, a clutch, a nozzle or a deformation tool.