An Afm Investigation of Thin Lubricious Coatings

Abstract

A multifunctional atomic force microscopy (AFM) instrument has been used to investigate the surface characteristics of two proprietary lubricious coatings applied to hardened and tempered low alloy steel substrates. The coating materials, MoST (MoS₂-Ti) and carbon based Graphit-ic, were applied using magnetron sputter deposition technology. The short range roughness of the coatings (R_a and R_q) was in the range 4 - 7 nm. AFM phase contrast imaging revealed that the MoST coatings had a lateral grain size of 400 nm, whilst the Graphit-ic coatings had duplex lateral grain size of 400 and 600 nm. No second phase constituents were detected. The MoST coatings had a hardness of 33.2 ± 3.6 GPa, whilst the Graphit-ic coatings had a hardness of 16.4 ± 0.8 GPa. The MoST coatings were more scratch resistant than the Graphit-ic coatings and were probably also more resistant to abrasion.