ABSTRACT In this experimental study, the influence of various surface treatments on a number of performance metrics of lubricated rolling-sliding contacts are investigated。 The surfaces considered are (i) hard ground surfaces at root-mean-square roughness amplitudes of about 0。4 m, (ii) chemically polished surfaces with an isotropic texture at roughnesses of about 0。1 m,

(iii) highly polished surfaces representing extremely smooth conditions at about 0。02 m and (iv) chemically applied NiB coated surfaces。 These surface treatments are applied to two types of case-hardened base materials: (i) AISI 5120 alloy steel representative of automotive gear steels and (ii) AISI 9310 steel representing the most common aerospace gear steel。 A two-disk test methodology is developed to test these specimens with two types of oils: 80W90 that is a typical ground vehicle fluid and MIL-PRF-23699 as a representative of aerospace gear oils。 With operating conditions defined by normal load (contact pressure), rolling (entraining) speed, slide- to-roll-ratio, oil inlet temperature and oil flow rate, three types of two-disk experiments are performed to evaluate the performance of these surface treatments。 These consist of traction (friction coefficient) tests at various rolling speeds and normal loads, long-cycle wear tests at extreme sliding conditions, and scuffing tests under constant speed and incrementally increasing load conditions with normal and starved oil flow rates。 Results of these two-disk experiments clearly show that a reduction in surface roughness amplitudes results in significant reductions  in the friction and wear coefficients, while enhancing the scuffing performance of the contacts even under starved lubrication conditions。76206

The same surface treatments are also applied to unity-ratio spur gear pairs to quantify their impact on the power losses of gear pairs。 In line with the their respective friction coefficients, smoother surfaces are shown to result in lower mechanical power losses while the spin losses remain unchanged regardless of the surface treatment。

Throughout both two-disk and spur gear experiments, NiB coated test surfaces are observed to lack the required durability to provide any tangible improvements over baseline ground surfaces。 Traction and wear tests with NiB coated rollers are seen exhibit peeling off and accelerated wear of the coating layer。 The same level of deterioration is observed in the gear efficiency tests as well。

Dedicated to my two daughters。

ACKNOWLEDGMENTS

I would like to express my sincere appreciation to Dr。 Ahmet Kahraman for providing me the opportunity to work alongside him and learn from him as a research engineer within the Gear and Power Transmission Research Laboratory。 I also wish to thank him for allowing me to complete my master’s degree coursework while still being a full time employee of his lab。 I also would like to express my sincerest gratitude to Dr。 Donald Houser for his support since I first met him when he hired me as an undergraduate so many years ago。 I would like to thank the project sponsor, Army Research Lab, for the support and assistance。

I would also like to say thank you to Jonny Harianto for his continuing friendship throughout my time with the GearLab。 I would also like to thank the graduate students of the GearLab for providing necessary laughter during both working and testing。

I finally would like to thank my wife for her endless encouragement, as well as the necessary motivation during this endeavor。 Her support throughout this has been the framework for which I can say this degree is built upon。

VITA

December 25, 1981 Born – Dayton, Ohio

Sept。 2001 – March 2005 Undergraduate Research Assistant