Tag: Alloy 718 bolts for high temperature strength

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.

Inconel Bolt Fastening to Titanium in High Temperature

Q: I have an application in which I require a 1/2in-13 Hex bolt that will be in an inert gaseous environment at 500C. The bolt will be fastened to a Titanium Grade 5 nut. What material bolt would work best?

A: I would suggest either Inconel 625 or Inconel 718 for your application. It just depends on how much strength you need. The Inconel 718 is very strong with a min Tensile of 180KSI while Inconel 625 has a min or 120KSI. As long as you stay below 700C you should be OK with the Inconel 718 and the Inconel 625 can go to almost 1000C.