Ceramic-metal joints design

Rapid fluid flow cannot be achieved with active metal brazes because of the need to form solid wettable reaction product layers for their liquid fronts to advance. Equations (10.1) to (10.2) relating liquid flow rates to the opposed effects of surface energy imbalances and of viscous drag are not relevant. Actual penetration rates are so slow, usually of the order of 1 pm.s, that the usual practice is to place the active metal braze alloy within the joints rather than expecting it to fill them, and, as explained already, gap width is not the dominant consideration when designing ceramic-metal joints. 

The ability to compare the measured joint strength to the predicted residual stresses will allow the FEA model of the joints to be refined and will provide a tested method to aid in designing ceramic-metal joints in the future. 

The same capillary phenomena affect brazing practice for joining both ceramic and metal components, but the relative importance of the phenomena differs, and this makes it convenient to discuss their effects in a different sequence. Further, most joining of ceramics is to metals and the different thermal expansion and mechanical characteristics of these two families of materials, as exemplified in Table 10.4, have a profound effect on joint design that is not related to capillarity. 

For high-temperature gas separation applications, leak-free sealing of the ITM module components and parts is essential and requires chemically resistant ceramic-metal and ceramic-ceramic seals with similar mechanical, chemical, and expansion characteristics as the membrane material. Little prior art exists for sealing and joining designs for tonnage-quantity ITM modules. ITM ceramics are susceptible to breakage and will have to be joined preferably without any joint interface property difference, possibly as a routine plant maintenance procedure. 

KAERI has contributed to all working groups of Gen-lV VHTR material collaboration graphite, metal and design method, and ceramic and composite. By the end of 2014, 37 technical reports have been uploaded into the Gen-lV materials handbook. In addition, creep test records (45 data) of alloy 617 and tensile test results for the BM, WM, and weld joint of alloy 617 (32 ea) were uploaded into the Gen-lV materials handbook (Generation IV international fomm annual report, 2013). 

Most materials can be bonded with the correct selection of adhesive, surface preparation and joint design. Metals, plastics, composites, wood, glass, paper, leather and ceramics are bonded commonly. 

Joint Replacement. Frequently the joints in the human body must be replaced because of disease or injury. Hundreds of designs have been used in attempts to replace the wide variety of joints with plastics, ceramics, and metals in many combinations. Most of these attempts have had only limited success, but many joints can now be replaced with a reasonably satisfactory prosthesis and thereby restore much of the normal joint function. Essentially all of the most successful replacement joints use a polymeric material. 

This combination of materials has had a profound effect upon the development of surgery for the treatment of Joint disease and prostheses are readily available, not just for the hip joint but also for the knee, ankle, shoulder and other joints. It is the good biological acceptability of UHMWPE coupled with its mechanical properties that has led to this widespread acceptance. In particular, the tribological characteristics appear to be the most satisfactory for use in a metal-polymer combination. Prosthesis designs utilising alumina ceramic also incorporate an acetabular component of UHMWPE in consequence of the low rate of wear observed. 

Motis - A wear grade for bearing applications against hard counter-faces such as metal and ceramics. Designed for arthroplasty (joint formation) devices. 

---