Dry Sliding of Nitrided NiTiHf

Abstract

The unlubricated friction and wear properties of the superelastic material NiTiHf, treated by either gas nitriding or plasma nitriding, have been investigated. Pin-on-disk testing of the studied materials was performed at sliding speeds from 0.01 to 1 m/s at normal loads of 1, 5, or 10 N. For all of the studied friction pairs (NiTiHf pins vs. nitrided disks) over the given parameters, the steady-state coefficients of friction varied from 0.7 to 1.6, and those of the control (NiTiHf on NiTiHf) varied from 0.5 to 1.2. Pin wear factors ranged from approximately 10⁻⁶ against the NiTiHf and plasma-nitrided disks to approximately 10⁻⁴ for the gas-nitrided disks. The plasma-nitrided disks provided wear protection in several cases and tended to wear by adhesion. The gas-nitrided treatment generated the most pin wear but essentially no disk wear except under the most severe of the studied conditions (1 N load and 1 m/s sliding speed). The results of this study are expected to provide guidance for design of aerospace components such as gears and fasteners.

Keywords:

• Friction
• wear
• nitriding
• intermetallics

Acknowledgements

This study was made possible with the generous technical assistance I received from J. A. Buehler, B. N. Cook, Dr. W. D. Jennings, D. F. Johnson, R. A. Manco II, T. R. McCue, R. J. Pawlik, Dr. R. B. Rogers, K. H. Sirk, and F. Thomas. I am very grateful for the helpful technical discussions I had with Drs. R. J. Bruckner, C. DellaCorte, W. D. Jennings, T. L. Krantz, and E. A. Rolinski and with F.Thomas.

Additional information

Funding

This study was funded by the Transformative Tools and Technologies Project within NASA’s Aeronautics Research Mission Directorate.