Q: I am working on two different exhaust systems based on 409 SS. I am looking for a 3/8-16 1” long bolt which can be fastened to threads in 409 SS. Currently, I am using Grade 8 bolts made from 300 M with Nickel Based Anti-Seize. The temperature can go as high as 500 C. After some time when bolts are removed, some of them are breaking. What bolt material will be suitable in 500 Deg Celsius (932 Fahrenheit) temperature and can be used with threads in 409 SS?
A: A286 bolts are something you should definitely consider. A286 is a great high temperature material for bolts, as it is very oxidation resistant and well suited for your operating temperatures of 500C. As it is resistant to oxidation, you will be much less likely to enbrittle and break an A286 bolt. Additionally a moly-disulphide anti-seize is a good idea to help minimize any kind of galling. Here are some links that may help you.