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.

For lubrication in cold forging, pretreatment by shot blasting to workpieces is widely used to prevent galling and realize high lubrication performance for replacing conventional conversion coatings with environmentally friendly lubricants. Previous studies suggest that an appropriate surface topography on workpieces pretreated by shot blasting improves lubricant adhesion and lubrication performance. Shot blasting generates not only an appropriate surface topography but also freshly activated surfaces on workpieces. In this study, results of surface chemical analysis by X-ray absorption near edge structure (XANES) on a steel surface which is conducted pretreatment by shot blasting and lubricant application. In the lubrication, an environmentally friendly lubricant with phosphorus extreme-pressure additives is used under conditions of different interval times after shot blasting. It was found that lubricant application immediately after pretreatment by shot blasting raised the potential of lubrication performance, as shown by the results of the ball penetration test.