Effect of Prior Shot Blasting on Free Surface Roughening before Environmentally Friendly Lubrication during Plastic Deformation

Abstract

For lubrication in cold forging, environmentally friendly lubricants have been widely used to replace conventional conversion coatings. To prevent seizure and realize high lubrication performance in severe forging process such as enclosed gear forging, lubricants on workpieces should withstand extreme conditions during plastic deformation. Pretreatment shot blasting to the workpieces has been performed to improve lubricant adhesion and lubrication performance, and an appropriate surface topography has been discussed. In this paper, we present the effects of pretreatment shot blasting conditions on free surface roughening before lubrication. Shot blasting with spherical media forms a hardened layer on the workpieces. Intense roughening and partial exfoliation occur on the free surface of the lubricated workpieces after forging. However, another shot blasting with angular media maintains a finely roughened surface with the thin hardened layer on the workpieces after forging, which effectively prevents the exfoliation of the lubricant film.