A Fe-Ni-Cr alloy with excellent high temperature oxidation resistance

A-286 lock nuts are known for their high strength, creep resistance and oxidation resistance at elevated temperatures. This iron-nickel-chromium alloy (once age-hardened) provides A-286 lock nuts with high levels of strength from room temperature up to about 1300°F (700°C).

A-286 nuts are mildly corrosion resistant. While they should not be used for strong acid environments, they provide excellent oxidation resistance up to 1300°F (700°C) in conditions that would typically be found in high temperature exhaust streams.

Because of these properties, A-286 lock nuts are often found in high temperature engine, manifold, exhaust and turbine applications as well as off-shore oil & gas applications.

Resources: A-286 Torque Specs

 


A286 Locknut Features and Beneifts

A A286 locknut resists loosening from vibrations and torque. One of the most common styles is a prevailing torque locknut. This kind of A286 locknut has a prevailing torque feature which deforms elastically, preventing it from freely spinning like a standard nut.

The two most common and reliable forms of prevailing torque locknuts are the flexloc style and the polymer insert lock nut. A A286 flexloc nut is all-metal in composition with a segmented collar that creates six “locking fingers,” that act as a spring. A286 polymer insert lock nuts are often referred to as nylon insert locknuts, although various high performance polymers can be used for the screw threads to “bite into.” Both flexlock and polymer insert locknuts are available in both hexagonal and 12 point configurations.

 All Metal Flexloc Lock Nut          Flexloc Lock Nut  Polymer/Nylon Insert Lock Nut        Insert Lock Nut
  • Can be used at high temperatures
  • Distributes load evenly due to the fact that it is manufactured as one solid piece.
  • Is THE most reliable all-metal self-locking nut.
  • As it is all metal, it is best for high temperature or corrosive applications
  • One of the only all-metal lock nuts that is certified to 15 cycles of prevailing torque – which is military standard.
  • Overall the most reliable locknut, with the only limitation of application temperature
  • Best for low temp applications, typically less than 350°F
  • Various polymers inserts available (Nylon, Vespel, PVDF, etc.) for higher temp. or corrosive applications.
  • Excellent reusability – can reliably be re-used 15 times
  • Eliminates galling and cold-welding common with exotic alloys

Other all metal lock nuts available include the A286 stover and elliptical styles. Though these styles are often a cheaper initial cost, they are less reliable than the flexloc style. As these styles delivering less prevailing torque cycles and often result in more failures, the flexloc style is a better investment for both reliability and cost savings.

 


A-286 Chemistry, Specifications & Heat Treatments

A-286 Heat Treatments:  There are several heat treatment combinations for A-286 all with slight variations in performance. They can be specified via an AMS number or a 660 Class: A, B, C or D,  with most common specified as class A or D.   The A-286 grades A, B and C all have the same min tensile strength and min yield strength of 130ksi and 85ksi respectively. However grade D is significantly better yield with a min tensile of 130ksi and a min yield of 105ksi. 

By AMS numbers, the most common for A-286 is AMS 5737 (same as Grade A) and then AMS 5732 (same as Grade B). 

A-286 Specifications: AMS 5525, AMS 5732, AMS 5737, AMS 5804, EN 1.4980, GE B50T1181, GE B50T12, GE B50T81, UNS S66286, Werkstoff 1.4980

A 286 Chemistry


Mechanical Properties

A-286 Tensile Curves

 

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