Nickel based super alloys are utilized at high temperatures, in aggressive environments, and therefore important for aeroengine applications. RR1000 is a nickel-based superalloy, developed specifically for use in aeroengine turbines. This powder processed alloy resists cracking, corrosion and oxidation when subjected to extreme heat but is prone to micro cracking as the metal solidifies after undergoing conventional welding. Therefore inertia friction welding is currently being developed as a joining technique for this alloy. The cost effective design and safety requirements for aeroengine turbine, pose a fundamental challenge, demanding low residual stress in inertia friction welded RR1000 components. This experiment proposes to investigate the residual stresses in as weld and PWHT inertial friction welds of RR1000, with dissimilar microstructures i.e coarse grain welded with fine grain