The welding process induces residual tensile stress that is detrimental to fatigue life. Tensile stresses act to stretch or pull apart the surface of the material. With enough load cycles at a high enough tensile stress, a metal surface will initiate a crack. Significant improvements in fatigue life can be obtained by modifying the residual stress levels in the material. Two methods of performing this are through heat treating and shot peening. Both will be thoroughly analyzed in this paper through the use of x-ray diffraction. X-ray diffraction is the most accurate and best-developed method to characterize the residual stress in polycrystalline material.