An Inconel 600 Bolt vs an Inconel 625 Bolt

Q: Does Inconel 600 provide the same level of corrosion resistance as an Inconel 625 bolt?

A: Not typically. For corrosion resistance, an Inconel 625 bolt is one of the more corrosion resistant versions of the Inconel alloys and it can withstand many strong hot acids. While not as corrosion resistant as a Hastelloy C276 bolt, Inconel 625 bolts have more high temperature capabilities. As for Inconel 600 compared to Inconel 625 screws, 600 is the go to for high temperature nickel alloys and can withstand up to 2000F vs 1800F for Inconel 625.

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.

17-4 Corrosion Resistance to Sulfuric Acid & Inconel

Q: Are there any materials I can use with the strength of 17-4PH in the H1150 heat treat, but with better corrosion resistant properties. I have low levels of sulfuric acid and chlorides that seem to be attacking the 17-4 steel.

A: The best choice for both extreme strength and corrosion would be Inconel 718 bolts. Inconel 718 may be overkill as it can provide excellent corrosion resistance to concentrated acids and chlorides at high temperatures while boasting min yield of 175KSI. However if you are looking for a big improvement in both corrosion and strength this will do it. Another material worth considering would be Inconel 625. This is basically the un-aged sister material of Inconel 718 having good corrosion resistance and a strength similar to that of 17-4 H1150. Inconel 625 would a significant improvement in corrosion resistance to sulfuric acid over 17-4 PH while maintaining a similar strength.