Fully-funded PhD Studentship for UK/EU students

A 4-year PhD studentship is available in the Centre for Doctoral Training (CDT) in Theory and Simulation of Materials at Imperial College London.

The position is fully funded for EU and UK candidates.

Embrittlement of Ni-based superalloys by oxygen

To save fuel, and to minimise their impact on the environment, commercial jets now try to achieve cruising altitude as quickly as possible after take-off. As a result Ni-based superalloys in the engine are exposed to the highest operational temperatures and stresses for typically 10 times longer than they were originally designed for. This change has led to the occurrence of stress-assisted grain boundary oxidation (SAGBO) in which cracks appear and grow along grain boundaries in the superalloy, necessitating more frequent inspections.

This is a problem of stress-assisted diffusion leading to embrittlement and fracture. A crack forms at a grain boundary. Oxygen diffuses into the boundary and reacts chemically with the metal to form a brittle oxide particle ahead of the crack called an intrusion. The oxygen diffusion is enhanced by the tensile field of the crack and suppressed by the compressive stress within the oxide intrusion caused by its greater volume per metal atom than in the metal itself. Therefore, the stress state immediately ahead of the crack in the presence of the intrusion is a primary concern. The crack grows by fracturing the intrusion, and the intrusion grows by diffusion of oxygen through (or around) the intrusion. There is a steady state in which the rate of crack growth equals the rate of growth of the intrusion by stress-assisted diffusion.

The objectives of this project are to: derive a theory for the crack growth rate; carry out a sensitivity analysis for the crack growth rate; simulate the crack growth rate under realistic conditions; suggest ways in which the crack growth rate may be reduced or suppressed altogether.

Successful candidates will have an aptitude for theory and already have, or expect to achieve, a first class (or equivalent) Bachelor’s or Master’s degree in the physical sciences or engineering. The studentship will start in October 2014.

The project is in collaboration with Rolls Royce. Technical and scientific enquiries may be directed toProf Adrian Sutton FRS. General admissions enquiries should be directed to Ms Miranda Smith.