Investigation of the effects of shot peening on 50crv4 steel containing artificial surface defects

In this study, it is aimed to present the ability of shot peening process to rendere harmless of surface defects arising from material itself or manufacturing process in high-strength steels. Shot peening is a cold working process in which the surface of a part is bombarded with small spherical media called shot increasing the life, strength & performance of metal parts. It produces a compressive residual stress layer and modifyies the subsurface of metals. This application can be applied to a variety of materials and their welded components, such as steels, cast irons, copper and aluminum alloys, titanium alloys and some plastics. In this study, tools were manufactured at 90 ° and 150 ° angle and artificial surface defects were processed on 50CrV4 steel at depths of 0.2-0.4-0.6 mm. In addition, 2 mm deep transverse scratch and 3mm diameter hole were machined. The shot peening process with 10 Almen intensity were applied to the prepared test samples. The fatigue tests were performed by using 20 kN Sincoteck 3-bending fatigue machine with Power Swing Mot high frequency resonator at room temperature in avrg 45 Hz frequency at room temperature. The specimens were fatigued at a constant maximum stress until failure, or the test was stopped after starting of 1 Hz differences if the sample did not fail. The studied stress amplitudes corresponds to 50-75% of the material's 0.2% offset yield strength. The scratched and shot peened surfaces were placed at the bottom and then forces were applied right behind the scratch. As a result, it was found that SP is a useful technique for increasing the structural integrity of components subjected to cyclic stress, even if these components have a detrimental surface defect. It was presented that SP is also effective to regain the hardness loss due to decarburization which the parts can be subjected it during hardening. Keywords: Shot peening, Surface defects in steels, 50Cr 2020, 75 pages