Friction and wear mechanisms in MoS2/Sb2O3/Au nanocomposite coatings

Fundamental phenomena governing the tribological mechanisms in sputter deposited amorphous MoS2/Sb2O3/Au nanocomposite coatings are reported. In dry environments the nanocomposite has the same low friction coefficient as pure MoS2 (similar to 0.007). However, unlike pure MoS2 coatings, which wear through in air (50% relative humidity), the composite coatings showed minimal wear, with wear factors of similar to 1.2-1.4 x 10(-7) mm(3) Nm(-1) in both dry nitrogen and air. The coatings exhibited non-Amontonian friction behavior, with the friction coefficient decreasing with increasing Hertzian contact stress. Cross-sectional transmission electron microscopy of wear surfaces revealed that frictional contact resulted in an amorphous to crystalline transformation in MoS2 with 2H-basal (0 0 0 2) planes aligned parallel to the direction of sliding. In air the wear surface and subsurface regions exhibited islands of Au. The mating transfer films were also comprised of (0 0 0 2)-oriented basal planes of MoS2, resulting in predominantly self-mated "basal on basal" interfacial sliding and, thus, low friction and wear. (C) 2010 Published by Elsevier Ltd. on behalf of Acta Materialia Inc.