Incoloy 908, an iron-nickel base superalloy that was developed as a Nb3Sn jacket material for Cable-In-Conduit Conductors, has been selected as the jacket material for the International Thermonuclear Experimental Reactor (ITER) Toroidal Field (TF) and Central Solenoid (CS) coils. It has a coefficient of expansion matching Nb3Sn (to minimise Jc and Tc degradation due to differential contraction after the reaction heat treatment). The alloy exhibits a characteristic of iron-nickel base superalloys: oxygen embrittlement along grain boundaries as a result of heating in an oxygen atmosphere when tensile surface stresses are present. For applications using Incoloy 908, techniques are required to control levels of either oxygen or tensile surface stresses during heat treatment. R & D results performed to develop and qualify such techniques for industrial applications are presented. The work has concentrated on establishing the lowest achievable oxygen levels inside the cable space during the reaction heat treatment and determining the conditions that can be tolerated inside and outside the jacket before SAGBO occurs. The results were applied in the ITER Model Coil programmes, in which about 5.5 km of conductor have been successfully heat treated.