Effect of burnishing and deformation profiling of lubricating microcavities on topography parameters and hardening of flat-topped AISI 420 steel surface

Abstract

This article studies the effect of final finishing of tribological conjunction parts made of AISI 420 steel using a turn-mill center, consisting of successive transitions of finish turning, preliminary burnishing, deformation profiling of lubricating microcavities by a plateau-honing stone, and flat-topped burnishing on the alteration of a set of topography hardening parameters. The study was conducted with the use of optical tri-dimensional profilometry, scanning microscopy, and microdurometry methods. We analyzed the change of height, functional, functional-volumetric, and other surface topography parameters after each of the technological transitions. We also built bearing surface curves to visualize the change of parameters. The 3D-topography parameter analysis of the formed flat-topped surface with lubricating microcavities showed an almost 2.3-time increase in the void volume of cavities Vvv, and, respectively, in their oil absorption power, from 0.044 to 0.1 µm3 /µm2, as compared to a preliminary burnishing. Arithmetical mean deviation of the profile Sa, in comparison with a finish turning, decreased from 1.18 to 0.33 µm. Hardening rate of the original surface after transitions of final finishing amounted to 38.8 %. Microdurometry of the surface layer allowed to conclude that the Vickers pyramid application with a load of 2 N corresponds to the thickness of a burnishing-modified layer with a thickness of not more than 10 µm.