Q: Hi there! I have a set screw in a downhole Oil and Gas application that is experiencing cam out/stripping and seeking a recommendation for a drop in replacement. With 17-4 and stainless steel, galling is a real issue for us.  Also with the application being down-hole, if the screw is exposed to any kind of acid gases, sour gas, high levels of CO2 or well stimulation fluids for acidation, this could be causing corrosion as well.

A: If you are sure corrosion is not the issue and we focus on galling, the simplest thing to do would be to utilize a high performance anti-seize lubricant. A moly-disulphide based lubricant could really help with galling.  See the following link for more info (https://www.extreme-bolt.com/extreme-anti-seize-lubricant.html). If you are looking for a more robust solution, an upgrade in the metallurgy to a dissimilar material will minimize galling as well.

If corrosion is an issue, it may be best to upgrade to a material that is more stable in those acid conditions and less likely to gall. Depending on your strength requirements and conditions, a light nickel alloy like Alloy 20 may be suitable to a more engineering nickel alloy like Inconel 625. An Alloy 20 bolt is good for mild acids and salt water, can be used to 1000F and offers about 80 ksi of tensile strength. For a more robust materials you may want to look at an Inconel 625 bolt. These Inconel bolts will offer resistance to hot, strong acids. An Inconel 625 screw can be used to 1800F and offer about 144 ksi of tensile strength.