Mechanism Studies with Special Boundary Lubricant Chemistry

A mechanism was proposed in SAE Paper #941983, (October, 1994) to explain why “Unique Boundary Chemistry” (UBC) described in said paper (1) required an extended conditioning period for its full antiwear benefits to be realized and (2) why the UBC Chemistry produced a strong antiwear carryover effect, even after relatively short exposure to the engine. This paper will document and discuss results from several metal surface studies employing a variety of metal surface analysis techniques (XPS, Profilometry, and AFM) to support various aspects of the earlier proposed antiwear mechanism. These surface analysis studies were carried out with pertinent boundary lubricated parts from (a) bench tests, (b) engines tested under modified protocol Sequence IIIE conditions described in SAE Paper 941983 and (c) standard ASTM Sequence IIIE and VE tests exposed to the UBC Chemistry.