Investigation on thermal barrier coating and thermal behaviour at high temperature

Ding, Siwen

Investigation on thermal barrier coating and thermal behaviour at high temperature

Publication Date

July 13, 2017

Creator

Ding, Siwen

Abstract

The oxidation behaviour of diffusion and overlay coating, manufactured by pack cementation and high velocity oxygen fuel (HVOF) techniques, was studied under isothermal condition at a temperature of 1100 °C for up to 500 hours. Detailed analysis on oxide thickness coupled with cross section microstructure observation was carried out. The results shown sub-parabolic oxide growth for all samples. To simulate a real operating condition for the thermal barrier coating (TBC) system, high temperature oxy-acetylene flame based burner rig was designed, manufactured and calibrated. A maximum surface temperature of 1400 °C detected by a single wavelength pyrometer with a 700 °C through sample thickness thermal gradient was achieved. A TBC system in which the ceramic top layer deposited by air plasma spray (APS) technique was tested under such condition. Several damage/failure types were identified in comparison with samples tested under isothermal loading. A novel physical based mathematical moving boundary problem model utilizing asymptotic analysis that predicts the growth of the oxide layer on a binary bond coat system was proposed. The governing equations were discretized and solved numerically using finite difference and Newton’s iteration method respectively. Numerical results obtained from this model had shown a good qualitative agreement from comparison with the experimental studies.

Item Type

ethesis

Thesis Type

PhD

Supervisors