Whereas austenitic stainless steel fixtures will be fine for many low temperature, light loading, slow heating and cooling situations, the use of Inconels, Hastelloy materials and even ceramics may be needed for the more aggressive brazing conditions. Shown here is a table listing some of the commonly used fixturing materials and how they compare relative to elevated temperature strength and thermal shock resistance. As can be seen, the better that the materials can handle these situations, the higher the price tag associated with that fixture material (notice the exception with graphite).
As far as estimating an expected "life" (in months or years) for any fixture made from any of these materials, any number you choose for the life of that fixture is only a guess. The life of identical fixtures can vary significantly from brazing shop to brazing shop depending on how they are used or abused. For instance, here are five typical reasons (there are more) as to why it's hard to put an "expected life" on a brazing fixture:
1. Shop abuse
2. Heating/cooling rates
3. Temperatures used
4. Loading conditions used
5. Atmosphere quality
Next week we will look at these factors in detail.