Assessment of Mechanical Properties of 17-4 PH Stainless Steel Printed By Bound Metal Deposition (BMD)

Additive manufacturing (AM) is a modern technology that can produce parts from a 3D model by iteratively building the part layer by layer. Some of the benefits of using AM are reduced delivery times, storage needs, and design freedom due to AM being able to produce parts not possible using conventional methods. On the other hand, many well-known defects and residual stress are found in most AM methods. A newer AM process called Bound Metal Deposition (BMD) utilizes a different printing process that is significantly cheaper, easier to operate, and is expected to have almost no residual stress. However, significant defects running parallel to the printing lines have been identified in BMD. This thesis aims to investigate how these defects influence mechanical properties and fatigue capacity, with particular emphasis on variations across different printing orientations. The literature review showed that the mechanical properties of BMD, as well as those of powder bed fusion and direct energy deposition, depended on the direction of the defect relative to the applied force. Specimens, where the defects were parallel with the applied force, had the best mechanical properties, and specimens, where they were perpendicular, had the worst. Additionally, testing performed for this thesis found that specimens whose defects were at a 45-degree angle to the applied force were stronger than those with defects parallel to the printing direction, perhaps due to the mesh created by the lines changing direction iteratively layer by layer. Furthermore, a thorough interpretation of the effect of the defects on fatigue capacity found that the defects are prone to crack initiation and that vertically printed specimens are likely to have the worst fatigue capacity.