Welding-repair effect on F357-T6 aluminum castings: analysis of fatigue life

Demands for quality, complexity, and product integrity are crucial in the growing market of castings. Usually, the more complex is the manufacture of the casting, and the more difficult is to preserve the quality requirements. Additionally, casting manufacturing remains economically acceptable when the process scraps are limited in number. Welding repair can be adopted to eliminate some defectiveness due to the casting process although the effect of repairing on the mechanical performance of structural components has to be accounted. In this paper, a welding-repair procedure for cast aluminum samples, specifically designed to reproduce typical refurbishing of a complex full-scale cast frame, was implemented. A set of 14 weld-repaired aluminum samples was tested under fatigue loading condition, and the comparison with the unrepaired casts' behavior is presented. The statistical analysis was performed by Maximum Likelihood Estimation (MLE) method. The repaired casts belonging the Class 1Grade C assignment of the SAE Aerospace material specification (AMS 2175) show a slight lowering of the high cycle fatigue strength. However, in the higher stress regime, a reduction of the median fatigue life of the weld-repaired set was observed. Failure mechanisms of repaired cast samples were investigated and discussed.