Q: How do Alloy 625 and Hastelloy C276 bolts work together as far as galling goes?
A: Inconel 625 bolts and Hastelloy bolts should work well together. They have slightly different chemistries, which helps minimize galling. In addition, Inconel is a bit harder than Hastelloy, which also helps. As long as the mating parts are not going to extremely high temps, you should be OK. It definitely helps to use anti-seize lubricant to reduce the chances of galling even further.