Date of Award

12-1-2016

Degree Name

Master of Science

Department

Mechanical Engineering

First Advisor

Wiltowski, Thomasz

Abstract

In recent decade growing concerns of CO2 emissions from power plants have increased, which led to development of technologies like oxy-fuel combustion process. P91 steel is profoundly used in power plants, but oxy fuel combustion exacerbates corrosion due to recycling of flue gas. This paper studied the kinetics of the corrosion rate on the boiler tubes and furnace and help achieve a corrosion resistant coating over it. Refractory metal diffusion coating is created and tested at high temperature in corrosive atmosphere. This was done by forming Ti and Zr diffusion coating on P91 steel using pack cementation. Coating thickness of 12 and 20 µm were obtained for Ti and Zr respectively. These samples were tested in thermo-gravimetric system by heating at 950˚C for 24 hours in 5% oxygen in Helium gas. Heating in an oxidizing environment lead to exfoliation corrosion on uncoated P91 steel. TGA procedure confirmed less mass change of Ti and Zr coated samples, than that of uncoated P91 steel sample. SEM and depth profiling confirms oxygen penetration is 2.7mm in uncoated P91 steel sample, whereas the Ti and Zr Coated samples oxygen penetration is just 16 and 56 µm respectively.

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