Surface treatments such as cold expansion are widely used in industry in order to introduce compressive residual stresses in the bulk of the material in the vicinity of holes, up to 2mm beneath the surface. These compressive residual stresses are beneficial since they will prevent crack initiation from the surface and delay crack propagation originating from surface flaws for example. This experiment aims at characterising using neutron diffraction the residual stress fields below the surface in a Ni-base superalloy after cold expansion in order to incorporate the residual stresses within our models to predict its influence on initiation and crack propagation lives. In addition, residual stress relaxation after thermo-mechanical loading at high temperature will also be measured in order to assess the evolution of the beneficial residual stress during service and improve life prediction.