Research Projects

Fe and Ni-based alloys used in highly oxidizing environments in applications including fuel cell bipolar plates, spent nuclear reprocessing are pushed to operate in their transpassive regime. Transpassive domain is complicated by presence of additional reactions in addition to dissolution such as the water oxidation or oxygen evolution reaction, formation of secondary surface films, etc.. makes quantification and understanding of mechanisms only using conventional electrochemical measurements difficult. Therefore, we use a suite of complementary non-electrochemical techniques including Respirometry, Atomic emission spectroelectrochemistry (AESEC), and surface analytical tools such as X-Ray photoelectron spectroscopy (XPS) , and in situ X-ray absorption near-edge spectroscopy (XANES) that helps in deconvoluting competing processes taking place at the metal/electrolyte interface. 

Funding Agency: DFG (PI: Prof. Sannakaisa Virtanen) and Alexander von Humboldt Foundation (Sponsorship: Dr. Karthikeyan Hariharan)

2. High temperature oxidation of additively manufactured Ni-based superalloys

It is advantageous to use additively manufactured Ni-based superalloys to produce complex-shaped components used in jet engines thereby reducing the material wastage, machining costs, and production lead times. However, the AM process leads to unique microstructure (grain structure, dislocation substructure, elemental segregation) that can influence the properties including high temperature oxidation. The goal of this project is to understand the role of grain structure, carbide distribution on external scale formation and internal oxidation kinetics in EB-PBF processed Ni-based superalloy 247 benchmarked against commercial cast counterparts. The project combines high-resolution microscopy coupled with computational modeling. 

Funding Agency: Alexander von Humboldt Foundation (Sponsorship: Dr. Karthikeyan Hariharan)

3. High temperature oxidation novel Fe-based superalloys

A2-B2 superalloys based on Fe-Al-Cr-Ni are emerging as attractive alternative for Ni-based superalloys, Ferritic/Austenitic stainless steel up to 700-800C due to their low-cost, low-density with comparable mechanical properties. However, studies are limited with respect to high temperature oxidation. The goal of this project is to understand oxidation mechanisms in dry and wet air in connection to alloy chemistry and microstructure. Methods employed include Raman Spectroscopy and advanced microscopy to study the scale characteristics and underlying microstructure evolution. Furthermore, fundamental mechanisms of very early stage oxidation is studied using state-of-the-art in situ X-ray photoelectron spectroscopy.

Funding Agency: Alexander von Humboldt Foundation (Sponsorship: Dr. Karthikeyan Hariharan)