The Evaluation of Ammonia/Hydrogen Combustion on the H Permeation and Embrittlement of Nickel-Base Superalloys

Abstract

Recent studies exploring ammonia as a green hydrogen energy carrier have established its suitability for a variety of combustion technologies including gas turbines, furnaces, and internal combustion engines. Of significant interest are ammonia/hydrogen blends, which possess combustion benefits over pure ammonia, including an extended stability range and higher laminar burning velocity. Despite extensive research characterising the flame properties of these blends, very few studies explore the suitability of existing materials for the manufacture of ammonia/hydrogen combustors. The present study evaluates the impact of ammonia/hydrogen flame chemistry on the H permeation and possible loss of ductility of nickel-superalloys through exposing the samples to pure methane and ammonia/hydrogen flames at atmospheric pressure for a 5-hour period. The effect of the two flame compositions on the materials are compared through thermal desorption analysis (TDA) and room temperature tensile testing. The results showed that exposure to an ammonia/hydrogen combustion environment led to hydrogen being absorbed by the nickel superalloys but a possible variation in ductility is influenced by the combustion conditions. Furthermore, the formation of an oxide layer was shown to likely impact the hydrogen absorption rate of the materials. This work shows that ammonia/hydrogen flame chemistry on combustor materials should not be ignored and warrants further studies on material’s mechanical and environmental stability controlled by nitrogen and hydrogen species permeating at industrially relevant conditions.

Flame–Solid Interaction: Thermomechanical Analysis for a Steady Laminar Stagnation Flow Stoichiometric NH3–H2 Flame at a Plane Wall

“…One study of stainless steels and nickel-base alloys, tested at 793 K and 10 MPa pressure for 100 h, found that alloys containing >23% Cr were more resistant to corrosive attack of intermediate compounds. 19 Recent work 4 characterized various nickel-based alloys employed in the aerospace sector (e.g., Inconel, Hastelloy, and Nimonic) and the impacts that they suffer during combustion of ammonia/ hydrogen blends. The work was conducted using a swirling flame of low power (<10 kW) over a 5 h duration period.…”

“…Therefore, the design engineer of combustion applications must consider the efficient consumption/combustion of fuel and, meanwhile, the resulting mechanical loads, such as thermal stresses, which may destroy the structure. Of course, there are various other requirements, such as the H 2 embrittlement in the material (and nitration when using ammonia gas), in the design, and one can refer to, for example, refs , , and .…”