Characterisation of Residual Stresses in Machined Surfaces of a High Strength Nickel-Base Superalloy

The near surface residual stresses introduced by turning on a nickel-base superalloy RR1000 are studied. X-ray diffraction residual stress measurements have been made in both radial and circumferential directions as a function of depth. These show systematic changes in stress magnitude and depth profile. The extent of the plastic deformation has been determined by the variation of the diffraction peak width in the XRD measurement. Both the residual stresses and the plastic work have been found to vary sharply over the first 100 mu m. The variation in unstressed lattice spacing with depth points to a heat affected zone of 40 mu m in thickness.