Q: I’m working with a high temperature waste to fuel application that operates at 1000F normally but could spike to 1200F. Currently I am using Grade 8 bolts but I am concerned about the oxidation resistance of them and their stability at high temperatures.  Do you have any material recommendations? 

A: One of the best materials to consider for your high temperature application is A-286.  A286 bolts will be strong, oxidation resistant and thermally stable.  This will provide you will an significantly improved solution over Grade 8 alloy steel. An A286 bolt is also usable to 1300F.

Q: I have an high temperature exhaust application that requires about 130ksi of tensile strength and is running pretty hot at 1000F. There are also some low concentration acidic contaminants that condense on the bolts during shutdowns, that have caused corrosion in the past on standard 316 bolting. Would A286 work with this? It says it is mildly corrosion resistant.

A: An A286 screw is mainly used for high temperature / high strength applications that require oxidation resistance. ex would perform from a corrosion point of view in a very similar way to the 316 stainless steel bolts however it may be VERY difficult for you to differentiate if your “corrosion” problem is due to oxidation of the bolts or your mild acid or both. A286 bolts may solve your oxidation problem, which may be the initial cause of your “corrosion” problems as 316 is not very oxidation resistant. It may be a good test to do, if you can swap out some bolts

Q:How does Nitronic 60 compare to an A286 bolt for high temperature strength?

A: That depends on the strength required and the temperature of your application. A Nitronic 60 bolt is known for its high temperature properties up to 1800F. At these extreme temperatures it can offer good resistance to wear, fretting, and galling; and oxidation resistance comparable to that of 309 stainless. On the other hand it doesn’t offer the high strength of A286. Nitronic 60 offers 95ksi UTS compared to the 120-160ksi UTS of A286. A286 bolts offer excellent high strength, creep resistance and oxidation resistance to a temperature of 1300F – not as high as Nitronic. So it will depend on the temperature range and strength you require.

From thermal processing and furnace applications to the extreme demands of aerospace, several high temperature alloys are available each with unique traits and capabilities. This brief newsletter will outline the primary fastener materials that are commonly used for excellent high temperature and oxidation resistance.

Best High Temperature Oxidation Resistant Fasteners

ALLOY 330
Developed for furnace applications, Alloy 330 fasteners are ideal for high temperature oxidation and caburization resistance. They are one of few materials that can handle extreme temperature changes, plus alternate carburizing and oxidizing atmospheres. KEY TRAIT: Performance under cyclic heating &  cooling

INCONEL 625
Inconel 625 bolts deliver a unique package of corrosion, oxidation and carburization resistance combined with high temperature strength. Their nickel and chromium content provides resistance to a many of harsh chemicals including sulfuric acid. KEY TRAIT: Great high temp stability &  strength, in   even in corrosive environments

WASPALOY
Fasteners made from this unique alloy offer extreme temperature and oxidation resistance in combination with high strength. Waspaloy is one of the strongest fasteners available for use over 1300°F. KEY TRAIT: Extreme strength at high temperatures

A286 / ALLOY 660
Age hardened, Alloy 660 / A286 fasteners offer good oxidation and creep resistance, as well as high temperature strength. They are most commonly used in high temperature exhaust streams. KEY TRAIT: Very good strength at high temperatures

310SS
Offering good strength under mildly cyclic conditions. Alloy 310 fasteners also offer good resistance to oxidation, carburization, and other forms of hot corrosion. KEY TRAIT: Economic high temperature alloy for moderate strength applications