This research takes the principle of localised heat treatment using inert gas jets from concept to delivery of a working prototype system and its application on a specific component. Described is the development of this technology and proof of its thermal capabilities on a number of components and test pieces. Included are discussions on the atmospheric requirements of the system and the development of the system design to minimise the formation of significant oxidation and alpha case. Finally the later sections of this thesis detail the work carried out to understand the underlying principles of this technology and how this understanding can be read across to future applications. This is done in the form of process modelling; the output of this being boundary conditions which can be used to model this technology for a number of applications and geometries in the future.