Evaluation of the Tribological Property of Resin Coating by the Addition of Nylon and Graphite Particles 2012-32-0090
A resin coating was applied to a piston skirt for use in an
internal combustion engine to reduce the frictional resistance on
its surface. The purpose of the authors' study was to observe
the change in surface states with the addition of nylon and
graphite to the coating as solid lubricant particles in order to
investigate the tribological properties of the surface. The authors
observed self-formed microdimples on the resin surface when nylon
particles were added to the polyamide-imide (PAI) coating material.
These microdimples functioned as oil reservoirs similar in size to
the nylon particles.
The authors used PAI as a binder, and graphite particles (5 μm)
and two different grades (5 and 10 μm) of nylon-12 particles as
additives. These materials were mixed in a solvent, and an aluminum
test sample was coated. The test sample was then heated in an oven
to cure the PAI. Next, the texture of the surface was observed. The
tribological properties were measured with a ball-on-disk
tribometer under both oil lubrication and dry conditions.
When only graphite particles were added to PAI, microdimples did
not form on the surface of the coatings. However, the authors
observed microdimples when both nylon and graphite particles were
added. Sliding tests under oil lubrication showed a minimum value
of the friction coefficient when 3-5 vol% of nylon was added. The
addition of nylon particles to the graphite/PAI mixture decreased
the friction coefficient at slow sliding speeds. Under the dry
condition, the addition of a small amount of nylon did not affect
the coefficient, but the friction coefficient decreased as the
amount of graphite particles increased.