Tribological Properties of Embedded Solid Lubricant Coatings Fabricated by Patterning Methods

In this work we have investigated the tribological properties of embedded solid lubricant coatings and compared them to monolithic and alloy films of the same constituents. Lithographic patterning methods were used to create two-component coatings in which columns of MoS₂ were embedded in a Ti matrix. Coatings were deposited using rf sputter deposition, and co-deposition of MoS₂ and Ti was used to deposit the alloy coatings. A pin-on-disk (POD) test was used to examine the frictional behavior and mechanical stability of the coatings, and was carried out in both low and high humidity conditions. Optical and scanning electron microscopy (SEM) was used to examine the morphology of the wear track after the POD test. Coatings of MoS₂ alone were found to perform well under low-humidity conditions, but poorly under high humidity. Alloying of MoS₂ with Ti was found to provide some improvement under high humidity. The patterned film, which consisted of 2 μm diameter pillars of MoS₂, spaced 10 μm apart and embedded in a Ti film, was found to exhibit friction and wear properties superior to either Ti or MoS₂ alone. The coatings investigated here have potential applications for cutting tools and metal forming dies that will enhance tool life and reduce the energy expended due to frictional forces.