Ceramic Shot-Peening of a Landing Gear Component

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Shot peening is a cold working process in which the surface of a structural part is bombarded with small spherical medium called shot. The shots cause plastic deformation of the metal surface, which results in high compressive residual stresses in the area right beneath the dents. Since fatigue cracks generally originate at the surface of a part, compressive stresses induced by shot peening provide considerable increase in the part life.Landing gear flange pins are traditionally shot-peened by steel shots. However, the steel shots leave residue such as particle embedment, which could be detrimental to the service life of the pins. Also, the overall process using steel shots is lengthy. The most important is that during the high impact bombardment, the spherical shaped steel shots are plastically deformed (change the shape) and are not reusable. Therefore, the industry is trying to adopt ceramic shots that are not only reusable, but also give smoother surface finish and very low level of particle embedment/contamination.The objective of the proposed research is to investigate the possibility of replacing steel shots with harder ceramic shots. The surface quality after ceramic shot peening will be determined by measuring the roughness profile, the microstructure at the peened interface will be studied, and the residual stress will be measured from surface to the center of the specimen by XRD and stress profiles will be generated. The mechanical properties of the peened surface will be investigated via micro-indentation hardness and tensile testing, which will be compared with the unpeened specimen data.