Tag: A286 bolts compared to Inconel 718 bolts

Inconel 718 per NACE Specs

Q: What is the difference between Inconel 718 standard and NACE 718?
A: NACE stands for the National Association of Corrosion Engineers. This group puts forth standards for corrosion resistant materials and when the NACE certification is asked for, the user is typically asking for NACE MR0175. Inconel 718 that meets NACE MR0175 specs is produced in accordance with the American Petroleum Institute, specifically for the oil & gas industry, and geared to minimize stress corrosion cracking. 
 
NACE Inconel 718 have slightly different chemistry and mechanical properties than standard UNS N07718, ASTM or AMS Inconel 718.  The chemistry has a tighter element range and mechanically the material is less brittle and more ductile.  As a result, the tensile, yield and hardness of NACE Inconel 718 are lower.

Inconel 718 compared to A286 for High Temperature Strength

Q: We are currently using A286 bolts per ASTM 453 at 1200F and are having some issues with durability as the tensile strength we originally calculated necessary was 130ksi but seems like we need higher strengths. Any ideas?

A: In this type of environment you should consider A-286 in the cold-worked condition. This will give you a minimum tensile of 160ksi. If this is not enough strength, the next step would be Inconel 718 bolts. Inconel 718 can handle the same temperatures as A286 with a usability of up to 1300F. In contrast to A286 screws, Inconel 718 bolts are much stronger with a min tensile 180ksi.