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Abstract
Laser surface texturing (LST) is an emerging, effective method for improving the tribological performance of friction units lubricated with oil. In LST technology, a pulsating laser beam is used to create thousands of arranged microdimples on a surface by a material ablation process. These dimples generate hydrodynamic pressure between oil-lubricated parallel sliding surfaces. The impact of LST on lubricating-regime transitions was investigated in this study. Tribological experiments were carried out on pin-on-disk test apparatus at sliding speeds that ranged from 0.15 to 0.75 m/s and nominal contact pressures that ranged from 0.16 to 1.6 MPa. Two types of oil with different viscosities (54.8 cSt and 124.7 cSt at 40°C) were evaluated as lubricants. Electrical resistance between flat-pin and laser-textured disks was used to determine the operating lubrication regime. The test results showed that laser texturing expanded the range of speed-load parameters for hydrodynamic lubrication. LST also reduced the measured friction coefficients of contacts that operated under the hydrodynamic regime. The beneficial effects of laser surface texturing are more pronounced at higher speeds and loads and with higher viscosity oil.
ACKNOWLEDGMENTS
This work was support by the Heavy Vehicle Systems, Office of FreedomCar and Vehicle Technologies of the U.S. Department of Energy, under Contract W-31-109-Eng-38. The authors are grateful to program manager Dr. Sid Diamond for his support and encouragement.
Presented at the STLE/ASME Tribology Conference in Ponte Vedra Beach, Florida October 26-29, 2003
Final manuscript approved January 16, 2004
Review led by Itzhak Green
Notes
a Measured optical data; area includes bulges around dimples (unlapped).