Laser gas-assisted nitriding of Ti alloys

In general, titanium alloys are well known for their good mechanical and biocompatibility properties, but poor tribological behavior. Among other processes, laser nitriding has proven to be a promising way to improve the poor tribological behavior of titanium alloys. The current chapter will review the laser-nitriding technique with respect to enhancing the wear performance of titanium alloys. The chapter will explain why laser gas-assisted nitriding is a promising way to improve the wear resistance of titanium alloys. It will discuss different technological approaches to laser nitriding with respect to laser equipment and the required nitrogen atmosphere, and how plasma may aid nitriding efficiency. Further, specific characteristics of the solidification process during laser nitriding will be presented. Comprehensive results on the hardness and cavitation erosion resistance of laser-nitrided titanium alloys will be mentioned, and the fatigue behavior of the laser-nitrided alloy Ti-6Al-4V with derived correlations between the structure and mechanical properties as well as wear resistance will be shown. Finally, conclusions on the applicability and the benefit of the laser-nitriding process and directions for future developments in this field are given.

1. Introduction // 2. Nitriding, Carburizing, and Other Surface Treatments / 2.1. Gas Nitriding / 2.2. Salt Bath Nitriding / 2.3. Plasma Nitriding / 2.4. Ion Implantation / 2.5. Plasma Immersion Ion Implantation / 2.6. Laser Nitriding // 3. CW-Mode Laser Nitriding / 3.1. Processing Technologies / 3.2. Phase Formation and Structural Evolution / 3.3. Mechanical Properties and Wear Behavior // 4. Pulsed Laser Nitriding / 4.1. Ultra Short Laser Irradiation - the Femtosecond Nitriding / 4.2. Nanosecond-Pulsed Treatments / 4.3. Microsecond-Pulsed Nitriding / 4.4. Macro-Pulsing-Nitriding on the Millisecond Time Scale // 5. Plasma-Assisted Nitriding / 5.1. Conventional Plasma Nitriding / 5.2. Laser Assisted versus Conventional Plasma Nitriding // 6. Conclusion // 7. Acknowledgments // 8. References