Heat treatment processes can generate steep residual stress (RS) gradients and plastic deformation in metal components due to differential cooling and other effect such as phase transformation. The magnitude of residual stresses generated, and how quickly they vary spatially, will depend upon the material itself and the temperature gradients introduced during the heat treatment process. X-ray diffraction (XRD) techniques can be used to characterize residual stresses, as well as microstructural changes, including dislocation density and particle size in heat treated components. Plain carbon steel cylinders were heat treated, quenched and characterized using these methods. Residual stress measurements were performed via XRD using the Sin2Ψ technique and microstructural characterization was evaluated using the associated peak widths. Measurements were carried out both at the surface and through depth using electropolishing. The results indicate triaxial stress gradients exist in all samples investigated, with concomitant varying microstructural characteristics.