Ion-sulfurized lubricating gradient material (LGM), is a state-of-the-art technology conferring excellent
anti-friction and wear-resistant characteristics on metallic parts including gears, splines, and bearings. It
is characterized by a sulfur-proliferated zone composed of sulfides and sulfur-metal solid solution case
with smooth sulfur compositional gradient inside the underlying bulk. A variety of metals and alloys,
including steels, cast irons, super-hard alloys, and bronze, are suitable for ion-sulfurization. This
treatment is carried out at low temperature; therefore, geometric integrity, microstructure and mechanical
properties of the bulk are not compromised. It provides excellent solid lubrication which increases power
efficiency and inhibits adhesive wear, seizure and scuffing in gears. Moreover, the micro-porous
morphology in LGM’s surface accommodates lubricating additives. It improves run-in efficiency of
machinery/automotive units. The contact fatigue in gears and splines is noticeably reduced. The
tribological property of the LGM layer on steel parts can survive an extraordinarily high temperature,
which is rarely surpassed by other processes. With LGM, carbon/alloy steels can be used to substitute
for certain copper alloys in manufacturing specific gears. It fulfills the requirement for maintaining
stronger bulk while achieving superior friction/adhesion/run-in characteristics. In this article, the
engineering characteristics of LGM technology are introduced, and exemplary applications are presented.