Interaction of stainless steel threaded fasteners with stainless steel locking inserts

Abstract

The interaction of stainless steel threaded fasteners with stainless steel locking inserts was investigated with special emphasis on high-vacuum environment applications. Nondestructive and destructive test methods were used in conjunction with information gathered from investigation with a scanning electron microscope coupled with an Energy Dispersive X-ray Spectrometer.

Since high-vacuum environment applications require very limited use (if any) of lubrication for threaded fastening systems, galling between the threaded fastener and the locking insert was determined to be the major concern. Galling occurs at the highly loaded thread interface of the components and is attributed to the adhesive and sliding wear conditions that exist between the two.

Separation between the threads of the threaded fastener and the threads of the locking insert is more important in reducing galling potential then the use of a stronger stainless steel fastening material. For high-vacuum environments, the use of a 0.0001 inch thick flash silver plating on the locking insert provided the best results of the galling reduction methods tested.