A Novel Approach to Study the Sulfidation Kinetics of Ti-6Al-4V with and Without Iodine for Additive Manufacturing Applications

With the recent developments of self-terminating etching methods for post-processing of 3D printed alloys, there is a need to characterize and qualify these methods to better understand and implement the processes in the industry. One of the methods for post-processing of Ti-6Al-4V (Ti64) is sulfidation followed by the dissolution of the resulting sulfides in an acidic solution while protecting the base alloy. Ti64 reacts with sulfur to form a sulfide scale of the respective metal sulfides at high temperatures. However, the sulfide scale formed is fragile, and it is difficult to characterize the scale to study the kinetics of the sulfidation process. To address this, we propose a novel approach to study the high-temperature corrosion of Ti64 in sulfur and sulfur with iodine environments in this work. The thickness of the metal consumed is used to study the kinetics instead of the scale thickness. The novel approach uses a modified combination of the Arrhenius equation, random walk theory, Pilling-Bedworth ratio, and parabolic oxidation law to determine the activation energy and the pre-exponential factor. In addition, we introduce a new term called “consumption co-efficient” that can be used to predict the amount of metal consumed for different sulfidation temperatures and durations. It was found that the addition of 1 at. % iodine almost doubles the amount of Ti64 consumed. However, the surface finish was rougher than that from only sulfur sulfidation.