Cyclic steam oxidation of a steel for biomass power plant application

Mobbs, Rebecca-Louise (2018). Cyclic steam oxidation of a steel for biomass power plant application. University of Birmingham. Eng.D.

Preview

Mobbs18EngD.pdf
PDF - Accepted Version
Download (14MB)

Abstract

Austenitic stainless steels are commonly used as heat exchanger tubing in power plants. As a result, this class of steels have been optimised to withstand high temperatures and pressures. However, under these conditions, the alloy will experience oxidation which greatly affects the lifetime of the materials. The increased likelihood of more cyclic operating conditions means a greater level of understanding of the oxidation and spallation behaviour of these alloys is required. High temperature oxidation studies available in the literature principally emphasise isothermal oxidation of flat plates rather than curved surfaces representative of boiler tubing.
The isothermal and cyclic steam oxidation and spallation behaviour of TP347H FG was studied in this thesis. Electron microscopy and elemental characterisation showed the oxide encompasses an inner Fe-Cr-Ni spinel and an outer magnetite layer. A haematite layer forms during initial stages of oxidation in air-saturated steam conditions similar to the oxides formed in plant.
The use of a novel technique, termed STORME, made it possible to identify the chemistry of the spalled oxide and also allowed calculations of the interfacial fracture energy to be made and the spallation mechanism to be identified. Modelling of the spallation observed enables predictions of spallation behaviour to be made.

Type of Work:

Thesis (Doctorates > Eng.D.)

Award Type:

Doctorates > Eng.D.

Supervisor(s):