Applicability of micro shot peening as surface modification for rolling sliding interface

Author:  H. Usami, Y. Takizawa, K. Chou, Y. Yamada and M. Ando
Source:  Conf Proc 2014: ICSP-12 Goslar, Germany (pgs.552-557)
Doc ID:  2014136
Year of Publication:  2014
Abstract:  
The present study describes the applicability of micro shot peening as surface modification for reduction of friction loss of thrust needle roller bearing. A micro shot peening system capable of controlling the flow rate and the impact speed individually was developed. The impact media was fine steel beads (50 μm in size) coated with polytetrafluoroethylene (PTFE) powder. The bearing ring and the washer surfaces of the thrust needle roller bearing were shot peened using the developed apparatus. After the peening, transfer of the PTFE from the impact media to the target was confirmed by measuring the contact angle of the oil droplet on the surface. The results indicate that the contact angle was large and the PTFE coated selectively into the dents. Friction properties were evaluated with rolling/sliding and sliding experiments. It was found that the friction loss of the PTFE coated surface decreased in the rolling/sliding and the sliding conditions. The profile measurement and observation of the surface showed that PTFE coating resulted in the restriction of the transfer during the sliding contact. Therefore, it is concluded that the micro shot peening with the PTFE coated beads is an effective means to decrease the friction loss of thrust needle roller bearing.