Surface Characterization of Three-Layer Organic Coating Applied on AISI 4130 Steel

Abstract

Resin-bonded molybdenum disulfide (MoS2) is widely applied as a solid lubricant. However, multiple coatings are usually required to meet other requirements in mechanical systems. In this study, a quenched and tempered AISI 4130 steel was used as the substrate, being shot blasted. Furthermore, three layers were successively deposited: a zinc phosphate layer, a phenolic resin (basecoat), and a topcoat based on MoS2. The thicknesses of different layers were obtained by scanning electron microscope and by the ball-cratering method. 3D surface roughness parameters were determined for each step of manufacturing, following three approaches: average values, isotropy level, and distribution of heights. The ball-cratering method was successfully applied for determining the thickness of the zinc phosphate but presented a relative deviation for the others layers. The phosphating step was decisive for the final surface topography of resin-bonded coating in terms of distribution of heights. On the other hand, the isotropy level imposed by the shot blasting of steel was practically unaltered by all manufacturing processes.