WEAR AND SLIDING-FRICTION CHARACTERISTICS OF STAINLESS STEEL SS316LN WITHOUT A COATING AND WITH A CrN COATING AT ELEVATED TEMPERATURES AND IN A VACUUM

Stainless steel of type AISI 316LN - one of the structural materials of fast neutron reactors - must have a long service life under conditions that subject it to different types of wear (galling, adhesion, fretting, and abrasion). Cobalt-based hard facings are generally avoided due to induced radioactivity. Nickel-based hard facings are strongly preferred instead. One alternative to both types of coatings is a hard-alloy coating of CrN. This article examines wear and friction characteristics during the sliding of uncoated steel SS316LN and the same steel with a CrN coating. In addition, a specially designed pin-on-disk tribometer is used to perform tests in a vacuum at temperatures of up to 1000 degrees C in order to study the effect of oxygen on the wear of these materials. The morphology of the wear surface and the structure of the subsurface were studied by scanning electron microscopy. The formation of an adhesion layer and the self-welding of mating parts are seen to take place in the microstructure at temperatures above 500 degrees C. It is also found that steel SS316LN undergoes shear strain during sliding wear. The friction coefficient depends on the oxygen content, load, and temperature, while the wear rate depends on the strain-hardening of the surface of the material being tested.