Tribological Studies of Lubricated Laser-Textured Point Contacts in Rolling/Sliding Reciprocating Motion with Investigations of Wettability and Nanohardness

Abstract

The friction and wear behaviors of concentrated point contacts formed between lapped bearing steel balls and lapped/laser-textured flat bearing steel surfaces were studied in the boundary/mixed lubrication regimes under reciprocating rolling and sliding motions. Nanohardness variation in the vicinity of the dimples of the textured surface along with lubricant's wettability of the lapped and textured flat surfaces were measured to understand the tribological behaviors at the concentrated contacts. Moreover, the morphologies of wear debris collected from the contacts were investigated using analytical ferrography and scanning electron microscopy (SEM). It has been observed based on the experimental studies under the adopted operating parameters that the friction coefficient reduces to 33 and 27% at the rolling velocity (0.12 m/s) and sliding velocity (0.16 m/s), respectively, at the heavy load (P_H > 0.7 GPa) at the textured point contacts in comparison with lapped point contacts. However, at the light load (P_H ≤ 0.7 GPa), the friction coefficient increases or remains the same with respect to the lapped point contact in rolling motion. The specific wear rates of the balls of the contact (formed between the ball/textured surface) found more (varying in the range 9–69%) in comparison with the balls of the ball/lapped surface contact for all sliding velocities adopted in the investigation.

KEY WORDS:

• Laser Texturing
• Friction
• Wear
• Wettability
• Nanohardness
• Ferrography

ACKNOWLEDGEMENT

The authors acknowledge the help of Taruna Bansala, research scholar, IIT Delhi, in conducting the wettability tests.