Inconel 625 for Oxidation Resistance and Acid Contamination

Q: I have a process that is running at high temperatures that can fluctuate up to 1500F that requires not only oxidation resistance but also some chemical resistance contaminants. I had tried some C276 bolts for the stray acids but they don’t seem to be working mechanically…suggestions?

A: A good bolt to try may be an Inconel 625 bolt. They can handle much higher temperatures up to about 1800F. These Inconel bolts also can provide excellent oxidation resistance and can also provide protection against reducing chemicals like stray acid contaminants.

Inconel 625 vs Nitronic 60

Q: Can you explain to me the difference between Inconel 625 and Nitronic 60 in terms of high temperatures? Both seem to be able to handle temps up to 1800F but which is better?

A: Well that depends on what you are using them for. Inconel 625 bolts are a nickel-chrome based alloy and not only offers high temperature capabilities but it also has excellent corrosion resistance. Inconel 625 bolts provide very good resistance to corrosive chemicals like hydrochloric and sulfuric acid, and are almost completely resistant to salts. Furthermore Inconel 625 fasteners have a typical tensile strength of 144ksi and will maintain its strength to about 1200F before starting to drop and maxes out around 1800F.

On the other hand, Nitronic 60 fasteners are stainless steel based and cannot offer the robust level of corrosion resistance or high temperature strength as Inconel. Nitronic 60 bolts are known for good resistance to wear, fretting, galling and oxidation resistance even at elevated temperature and have a typical tensile strength of 95ksi. Nitronic 60 will max out at about 1800F as well.

Inconel 625 Bolts for 1650F Exhaust Duct

Q: I need fasteners for an exhaust duct where I want to use bolts to act as a stopper for a blast gate. The max temperature 1650F. Any suggestions?

A: In this type of environment, Inconel 625 bolts would be one of the strongest and most temperature resistant materials you could use at that temperature. There are not too many materials that would be better.

Inconel 625 for 900C High Temperature Application

Q: I have an application, which will be heated by radiant heat from below to 700°C to 900°C. The problem I am trying to solve is that the screws tend to fuse to the plate they are fastening. Black Oxide alloy steel is the best we’ve tried, but still very problematic. Any suggestions?

A: We definitely have some options that will help you. Probably the best option you have are Inconel 625 fasteners. This is a high temperature nickel alloy that is stable at temperatures over 900C. This will perform significantly better than the stainless steel you currently using, as you are readily oxidizing the materials causing them to fuse to your base plate. You should not have this problem with Inconel 625 screws.

In addition I would recommend using a molybdenum disulfide anti-seize lubricant. We offer one that is designed for high temperatures and will aid in the screws being more easily removed.