A new technology, duplex ion nitrocarburizing and sulphurizing technology (DINS), for
friction reduction and anti-scuffing applications of diesel engine cylinder was studied. Duplex ion
nitrocarburized-sulphurized layer was prepared on the surface of CrMoCu alloy cast iron by using
the DINS process. The morphology, phase structure and tribological behaviors under sulphur
contained additive lubrication were investigated. Results show that the sulphide surface layer of the
duplex layer is mainly composed of close-packed hexagonal structured FeS phase and cubic
structured FeS2 phase. The nitrocarburized sub-surface layer of the duplex layer is mainly
composed of Fe2C and Fe3N phases. The harder nitrocarburized layer can provide effective support
to the softer sulphide layer and avoid its lamellar tear. The synergistic effect between the duplex
layer and the sulphur contained additive lubricant, resulted in 10% and 33.3% reduction in coefficient
of friction and wear volume, respectively, compared with those of the sulphurized surface, and 25%
and 50.1% reduction, respectively, compared with those of the plain surface. Bench test of diesel
engine further demonstrated that the DINS process can provide the treated cylinder with superior
properties in anti-scuffing and friction reduction, so that it can be used to prolong the service life of
the cylinder.
