Ultrasonic impact treatment is a relatively new surface modification process that may be potentially applied to impart compressive residual stresses onto oilfield parts experiencing wear, fatigue, and possibly environmentally-assisted cracking. Through severe plastic deformation, ultrasonic impact treatment is herein investigated to surface harden two oilfield alloys, UNS N07718, a premium alloy with satisfactory oilfield performance but occasionally lacking surface hardness and abrasive wear resistance, and UNS G41400, a comparatively low-cost alloy restricted by its corrosion fatigue limit in oilfield rotating equipment. For comparison purposes, the two studied alloys were ultrasonic impact treated under identical conditions and carefully selected to exhibit similar yield strengths (900 MPa). Results from microstructural examinations, micro-hardness indentations, and residual stress measurements all indicate that ultrasonically treated surfaces exhibit superior properties that create opportunities for implementing this new surface modification process in selected oilfield applications.