Effects of ion implantation on microstructure, endurance and wear behavior of IBAD MoS2

Thin MoS2 coatings were prepared on steel and Si substrates via ion-beam assisted deposition using conditions known to produce dense, basal oriented microstructures. After deposition, the coated substrates were irradiated with 180 keV Ar2+ ions at doses of 1×1015, 1×1016, and 5×1016 ions/cm2. Microstructures of as-deposited and ion irradiated MoS2 coatings were examined using X-ray diffraction, high resolution transmission electron microscopy, and micro-Raman spectroscopy. Friction, wear and endurance were examined under both unidirectional and reciprocating sliding conditions in dry air. The lowest ion irradiation dose altered the initial microstructure, producing basal oriented, nearly defect-free crystalline domains of MoS2 in an amorphous matrix; at the highest dose the coatings were nearly amorphous, but the remaining MoS2 showed mixed orientation. Ion irradiation of the MoS2 coatings did not significantly modify the friction behavior, and only at the highest dose was the endurance altered, decreasing by more than 75%. Two changes in wear behavior were observed in the highest dosed coatings: (1) accelerated wear of the coating and (2) elimination of solid lubricant reservoirs. Destruction of the solid lubricant replenishment process resulted in premature failure of the highest dosed coating.