Gaseous Nitriding of Metastable Beta Titanium Alloys

Titanium is widely used and is well-established for many engineering applications spanning a broad range of industries with commercially pure and α+β alloys being the most popular systems. In many applications, the need for better tribological properties and high wear resistance is critical for optimal performance in, for example, biomedical implants, additive manufacturing, and for aerospace applications.

This research investigates the surface hardenability and material response to gaseous nitriding treatments of metastable β Ti-15Mo, Ti 15-3 (Ti 15V-3Cr-3Al-3Sn) and Ti Beta III (77.5Ti-12Mo-6Zr-4.5Sn) titanium alloys. These are compared with commercially pure Grade 4 and biphasic α+β Grade 5 (Ti-6Al-4V) alloys. Nitriding treatments of different durations, and at temperatures in the span 750-1050 °C, were carried out in a thermal analyzer where the simultaneous mass uptake and differential scanning calorimetry responses were recorded. Thermogravimetry is a useful in-situ method for the analysis of nitriding kinetics and for quantitative comparison of the nitriding response of different alloys. XRD phase analysis, optical microscopy and SEM/EDS are used to evaluate both the surface and bulk microstructure.